diff --git a/sherpa-onnx/csrc/CMakeLists.txt b/sherpa-onnx/csrc/CMakeLists.txt
index aa50c4ab..382541f9 100644
--- a/sherpa-onnx/csrc/CMakeLists.txt
+++ b/sherpa-onnx/csrc/CMakeLists.txt
@@ -155,7 +155,9 @@ if(SHERPA_ONNX_ENABLE_RKNN)
   list(APPEND sources
     ./rknn/online-stream-rknn.cc
     ./rknn/online-transducer-greedy-search-decoder-rknn.cc
+    ./rknn/online-zipformer-ctc-model-rknn.cc
     ./rknn/online-zipformer-transducer-model-rknn.cc
+    ./rknn/utils.cc
   )
 
 endif()
diff --git a/sherpa-onnx/csrc/online-ctc-decoder.h b/sherpa-onnx/csrc/online-ctc-decoder.h
index 65305e6a..4b01d678 100644
--- a/sherpa-onnx/csrc/online-ctc-decoder.h
+++ b/sherpa-onnx/csrc/online-ctc-decoder.h
@@ -43,12 +43,14 @@ class OnlineCtcDecoder {
 
   /** Run streaming CTC decoding given the output from the encoder model.
    *
-   * @param log_probs A 3-D tensor of shape (N, T, vocab_size) containing
-   *                  lob_probs.
+   * @param log_probs A 3-D tensor of shape
+   *                  (batch_size, num_frames, vocab_size) containing
+   *                  lob_probs in row major.
    *
    * @param  results Input & Output parameters..
    */
-  virtual void Decode(Ort::Value log_probs,
+  virtual void Decode(const float *log_probs, int32_t batch_size,
+                      int32_t num_frames, int32_t vocab_size,
                       std::vector<OnlineCtcDecoderResult> *results,
                       OnlineStream **ss = nullptr, int32_t n = 0) = 0;
 
diff --git a/sherpa-onnx/csrc/online-ctc-fst-decoder.cc b/sherpa-onnx/csrc/online-ctc-fst-decoder.cc
index dea90918..817450c9 100644
--- a/sherpa-onnx/csrc/online-ctc-fst-decoder.cc
+++ b/sherpa-onnx/csrc/online-ctc-fst-decoder.cc
@@ -91,30 +91,23 @@ static void DecodeOne(const float *log_probs, int32_t num_rows,
   processed_frames += num_rows;
 }
 
-void OnlineCtcFstDecoder::Decode(Ort::Value log_probs,
+void OnlineCtcFstDecoder::Decode(const float *log_probs, int32_t batch_size,
+                                 int32_t num_frames, int32_t vocab_size,
                                  std::vector<OnlineCtcDecoderResult> *results,
                                  OnlineStream **ss, int32_t n) {
-  std::vector<int64_t> log_probs_shape =
-      log_probs.GetTensorTypeAndShapeInfo().GetShape();
-
-  if (log_probs_shape[0] != results->size()) {
+  if (batch_size != results->size()) {
     SHERPA_ONNX_LOGE("Size mismatch! log_probs.size(0) %d, results.size(0): %d",
-                     static_cast<int32_t>(log_probs_shape[0]),
-                     static_cast<int32_t>(results->size()));
+                     batch_size, static_cast<int32_t>(results->size()));
     exit(-1);
   }
 
-  if (log_probs_shape[0] != n) {
-    SHERPA_ONNX_LOGE("Size mismatch! log_probs.size(0) %d, n: %d",
-                     static_cast<int32_t>(log_probs_shape[0]), n);
+  if (batch_size != n) {
+    SHERPA_ONNX_LOGE("Size mismatch! log_probs.size(0) %d, n: %d", batch_size,
+                     n);
     exit(-1);
   }
 
-  int32_t batch_size = static_cast<int32_t>(log_probs_shape[0]);
-  int32_t num_frames = static_cast<int32_t>(log_probs_shape[1]);
-  int32_t vocab_size = static_cast<int32_t>(log_probs_shape[2]);
-
-  const float *p = log_probs.GetTensorData<float>();
+  const float *p = log_probs;
 
   for (int32_t i = 0; i != batch_size; ++i) {
     DecodeOne(p + i * num_frames * vocab_size, num_frames, vocab_size,
diff --git a/sherpa-onnx/csrc/online-ctc-fst-decoder.h b/sherpa-onnx/csrc/online-ctc-fst-decoder.h
index 992276d6..430bad93 100644
--- a/sherpa-onnx/csrc/online-ctc-fst-decoder.h
+++ b/sherpa-onnx/csrc/online-ctc-fst-decoder.h
@@ -19,8 +19,8 @@ class OnlineCtcFstDecoder : public OnlineCtcDecoder {
   OnlineCtcFstDecoder(const OnlineCtcFstDecoderConfig &config,
                       int32_t blank_id);
 
-  void Decode(Ort::Value log_probs,
-              std::vector<OnlineCtcDecoderResult> *results,
+  void Decode(const float *log_probs, int32_t batch_size, int32_t num_frames,
+              int32_t vocab_size, std::vector<OnlineCtcDecoderResult> *results,
               OnlineStream **ss = nullptr, int32_t n = 0) override;
 
   std::unique_ptr<kaldi_decoder::FasterDecoder> CreateFasterDecoder()
diff --git a/sherpa-onnx/csrc/online-ctc-greedy-search-decoder.cc b/sherpa-onnx/csrc/online-ctc-greedy-search-decoder.cc
index e813c987..0ef14826 100644
--- a/sherpa-onnx/csrc/online-ctc-greedy-search-decoder.cc
+++ b/sherpa-onnx/csrc/online-ctc-greedy-search-decoder.cc
@@ -13,23 +13,16 @@
 namespace sherpa_onnx {
 
 void OnlineCtcGreedySearchDecoder::Decode(
-    Ort::Value log_probs, std::vector<OnlineCtcDecoderResult> *results,
+    const float *log_probs, int32_t batch_size, int32_t num_frames,
+    int32_t vocab_size, std::vector<OnlineCtcDecoderResult> *results,
     OnlineStream ** /*ss=nullptr*/, int32_t /*n = 0*/) {
-  std::vector<int64_t> log_probs_shape =
-      log_probs.GetTensorTypeAndShapeInfo().GetShape();
-
-  if (log_probs_shape[0] != results->size()) {
+  if (batch_size != results->size()) {
     SHERPA_ONNX_LOGE("Size mismatch! log_probs.size(0) %d, results.size(0): %d",
-                     static_cast<int32_t>(log_probs_shape[0]),
-                     static_cast<int32_t>(results->size()));
+                     batch_size, static_cast<int32_t>(results->size()));
     exit(-1);
   }
 
-  int32_t batch_size = static_cast<int32_t>(log_probs_shape[0]);
-  int32_t num_frames = static_cast<int32_t>(log_probs_shape[1]);
-  int32_t vocab_size = static_cast<int32_t>(log_probs_shape[2]);
-
-  const float *p = log_probs.GetTensorData<float>();
+  const float *p = log_probs;
 
   for (int32_t b = 0; b != batch_size; ++b) {
     auto &r = (*results)[b];
diff --git a/sherpa-onnx/csrc/online-ctc-greedy-search-decoder.h b/sherpa-onnx/csrc/online-ctc-greedy-search-decoder.h
index 0af37593..95f42541 100644
--- a/sherpa-onnx/csrc/online-ctc-greedy-search-decoder.h
+++ b/sherpa-onnx/csrc/online-ctc-greedy-search-decoder.h
@@ -16,8 +16,8 @@ class OnlineCtcGreedySearchDecoder : public OnlineCtcDecoder {
   explicit OnlineCtcGreedySearchDecoder(int32_t blank_id)
       : blank_id_(blank_id) {}
 
-  void Decode(Ort::Value log_probs,
-              std::vector<OnlineCtcDecoderResult> *results,
+  void Decode(const float *log_probs, int32_t batch_size, int32_t num_frames,
+              int32_t vocab_size, std::vector<OnlineCtcDecoderResult> *results,
               OnlineStream **ss = nullptr, int32_t n = 0) override;
 
  private:
diff --git a/sherpa-onnx/csrc/online-model-config.cc b/sherpa-onnx/csrc/online-model-config.cc
index 10fb2669..bfac64ec 100644
--- a/sherpa-onnx/csrc/online-model-config.cc
+++ b/sherpa-onnx/csrc/online-model-config.cc
@@ -76,6 +76,15 @@ bool OnlineModelConfig::Validate() const {
           transducer.decoder.c_str(), transducer.joiner.c_str());
       return false;
     }
+
+    if (!zipformer2_ctc.model.empty() &&
+        EndsWith(zipformer2_ctc.model, ".rknn")) {
+      SHERPA_ONNX_LOGE(
+          "--provider is %s, which is not rknn, but you pass rknn model "
+          "filename for zipformer2_ctc: '%s'",
+          provider_config.provider.c_str(), zipformer2_ctc.model.c_str());
+      return false;
+    }
   }
 
   if (provider_config.provider == "rknn") {
@@ -89,6 +98,15 @@ bool OnlineModelConfig::Validate() const {
           transducer.joiner.c_str());
       return false;
     }
+
+    if (!zipformer2_ctc.model.empty() &&
+        EndsWith(zipformer2_ctc.model, ".onnx")) {
+      SHERPA_ONNX_LOGE(
+          "--provider rknn, but you pass onnx model filename for "
+          "zipformer2_ctc: '%s'",
+          zipformer2_ctc.model.c_str());
+      return false;
+    }
   }
 
   if (!tokens_buf.empty() && FileExists(tokens)) {
diff --git a/sherpa-onnx/csrc/online-recognizer-ctc-impl.h b/sherpa-onnx/csrc/online-recognizer-ctc-impl.h
index 797d90f0..32f6ac4d 100644
--- a/sherpa-onnx/csrc/online-recognizer-ctc-impl.h
+++ b/sherpa-onnx/csrc/online-recognizer-ctc-impl.h
@@ -24,12 +24,11 @@
 
 namespace sherpa_onnx {
 
-static OnlineRecognizerResult Convert(const OnlineCtcDecoderResult &src,
-                                      const SymbolTable &sym_table,
-                                      float frame_shift_ms,
-                                      int32_t subsampling_factor,
-                                      int32_t segment,
-                                      int32_t frames_since_start) {
+OnlineRecognizerResult ConvertCtc(const OnlineCtcDecoderResult &src,
+                                  const SymbolTable &sym_table,
+                                  float frame_shift_ms,
+                                  int32_t subsampling_factor, int32_t segment,
+                                  int32_t frames_since_start) {
   OnlineRecognizerResult r;
   r.tokens.reserve(src.tokens.size());
   r.timestamps.reserve(src.tokens.size());
@@ -182,7 +181,10 @@ class OnlineRecognizerCtcImpl : public OnlineRecognizerImpl {
     std::vector<std::vector<Ort::Value>> next_states =
         model_->UnStackStates(std::move(out_states));
 
-    decoder_->Decode(std::move(out[0]), &results, ss, n);
+    std::vector<int64_t> log_probs_shape =
+        out[0].GetTensorTypeAndShapeInfo().GetShape();
+    decoder_->Decode(out[0].GetTensorData<float>(), log_probs_shape[0],
+                     log_probs_shape[1], log_probs_shape[2], &results, ss, n);
 
     for (int32_t k = 0; k != n; ++k) {
       ss[k]->SetCtcResult(results[k]);
@@ -196,8 +198,9 @@ class OnlineRecognizerCtcImpl : public OnlineRecognizerImpl {
     // TODO(fangjun): Remember to change these constants if needed
     int32_t frame_shift_ms = 10;
     int32_t subsampling_factor = 4;
-    auto r = Convert(decoder_result, sym_, frame_shift_ms, subsampling_factor,
-                     s->GetCurrentSegment(), s->GetNumFramesSinceStart());
+    auto r =
+        ConvertCtc(decoder_result, sym_, frame_shift_ms, subsampling_factor,
+                   s->GetCurrentSegment(), s->GetNumFramesSinceStart());
     r.text = ApplyInverseTextNormalization(r.text);
     return r;
   }
@@ -306,7 +309,10 @@ class OnlineRecognizerCtcImpl : public OnlineRecognizerImpl {
     std::vector<OnlineCtcDecoderResult> results(1);
     results[0] = std::move(s->GetCtcResult());
 
-    decoder_->Decode(std::move(out[0]), &results, &s, 1);
+    std::vector<int64_t> log_probs_shape =
+        out[0].GetTensorTypeAndShapeInfo().GetShape();
+    decoder_->Decode(out[0].GetTensorData<float>(), log_probs_shape[0],
+                     log_probs_shape[1], log_probs_shape[2], &results, &s, 1);
     s->SetCtcResult(results[0]);
   }
 
diff --git a/sherpa-onnx/csrc/online-recognizer-impl.cc b/sherpa-onnx/csrc/online-recognizer-impl.cc
index 810e0a17..c8f4c269 100644
--- a/sherpa-onnx/csrc/online-recognizer-impl.cc
+++ b/sherpa-onnx/csrc/online-recognizer-impl.cc
@@ -27,6 +27,7 @@
 #include "sherpa-onnx/csrc/text-utils.h"
 
 #if SHERPA_ONNX_ENABLE_RKNN
+#include "sherpa-onnx/csrc/rknn/online-recognizer-ctc-rknn-impl.h"
 #include "sherpa-onnx/csrc/rknn/online-recognizer-transducer-rknn-impl.h"
 #endif
 
@@ -37,12 +38,15 @@ std::unique_ptr<OnlineRecognizerImpl> OnlineRecognizerImpl::Create(
   if (config.model_config.provider_config.provider == "rknn") {
 #if SHERPA_ONNX_ENABLE_RKNN
     // Currently, only zipformer v1 is suported for rknn
-    if (config.model_config.transducer.encoder.empty()) {
+    if (config.model_config.transducer.encoder.empty() &&
+        config.model_config.zipformer2_ctc.model.empty()) {
       SHERPA_ONNX_LOGE(
-          "Only Zipformer transducers are currently supported by rknn. "
-          "Fallback to CPU");
-    } else {
+          "Only Zipformer transducers and CTC models are currently supported "
+          "by rknn. Fallback to CPU");
+    } else if (!config.model_config.transducer.encoder.empty()) {
       return std::make_unique<OnlineRecognizerTransducerRknnImpl>(config);
+    } else if (!config.model_config.zipformer2_ctc.model.empty()) {
+      return std::make_unique<OnlineRecognizerCtcRknnImpl>(config);
     }
 #else
     SHERPA_ONNX_LOGE(
diff --git a/sherpa-onnx/csrc/rknn/online-recognizer-ctc-rknn-impl.h b/sherpa-onnx/csrc/rknn/online-recognizer-ctc-rknn-impl.h
new file mode 100644
index 00000000..9edd45a4
--- /dev/null
+++ b/sherpa-onnx/csrc/rknn/online-recognizer-ctc-rknn-impl.h
@@ -0,0 +1,204 @@
+// sherpa-onnx/csrc/rknn/online-recognizer-ctc-rknn-impl.h
+//
+// Copyright (c)  2025  Xiaomi Corporation
+
+#ifndef SHERPA_ONNX_CSRC_RKNN_ONLINE_RECOGNIZER_CTC_RKNN_IMPL_H_
+#define SHERPA_ONNX_CSRC_RKNN_ONLINE_RECOGNIZER_CTC_RKNN_IMPL_H_
+
+#include <algorithm>
+#include <ios>
+#include <memory>
+#include <sstream>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "sherpa-onnx/csrc/file-utils.h"
+#include "sherpa-onnx/csrc/macros.h"
+#include "sherpa-onnx/csrc/online-ctc-decoder.h"
+#include "sherpa-onnx/csrc/online-ctc-fst-decoder.h"
+#include "sherpa-onnx/csrc/online-ctc-greedy-search-decoder.h"
+#include "sherpa-onnx/csrc/online-recognizer-impl.h"
+#include "sherpa-onnx/csrc/rknn/online-stream-rknn.h"
+#include "sherpa-onnx/csrc/rknn/online-zipformer-ctc-model-rknn.h"
+#include "sherpa-onnx/csrc/symbol-table.h"
+
+namespace sherpa_onnx {
+
+// defined in ../online-recognizer-ctc-impl.h
+OnlineRecognizerResult ConvertCtc(const OnlineCtcDecoderResult &src,
+                                  const SymbolTable &sym_table,
+                                  float frame_shift_ms,
+                                  int32_t subsampling_factor, int32_t segment,
+                                  int32_t frames_since_start);
+
+class OnlineRecognizerCtcRknnImpl : public OnlineRecognizerImpl {
+ public:
+  explicit OnlineRecognizerCtcRknnImpl(const OnlineRecognizerConfig &config)
+      : OnlineRecognizerImpl(config),
+        config_(config),
+        model_(
+            std::make_unique<OnlineZipformerCtcModelRknn>(config.model_config)),
+        endpoint_(config_.endpoint_config) {
+    if (!config.model_config.tokens_buf.empty()) {
+      sym_ = SymbolTable(config.model_config.tokens_buf, false);
+    } else {
+      /// assuming tokens_buf and tokens are guaranteed not being both empty
+      sym_ = SymbolTable(config.model_config.tokens, true);
+    }
+
+    InitDecoder();
+  }
+
+  template <typename Manager>
+  explicit OnlineRecognizerCtcRknnImpl(Manager *mgr,
+                                       const OnlineRecognizerConfig &config)
+      : OnlineRecognizerImpl(mgr, config),
+        config_(config),
+        model_(
+            std::make_unique<OnlineZipformerCtcModelRknn>(config.model_config)),
+        sym_(mgr, config.model_config.tokens),
+        endpoint_(config_.endpoint_config) {
+    InitDecoder();
+  }
+
+  std::unique_ptr<OnlineStream> CreateStream() const override {
+    auto stream = std::make_unique<OnlineStreamRknn>(config_.feat_config);
+    stream->SetZipformerEncoderStates(model_->GetInitStates());
+    stream->SetFasterDecoder(decoder_->CreateFasterDecoder());
+    return stream;
+  }
+
+  bool IsReady(OnlineStream *s) const override {
+    return s->GetNumProcessedFrames() + model_->ChunkSize() <
+           s->NumFramesReady();
+  }
+
+  void DecodeStreams(OnlineStream **ss, int32_t n) const override {
+    for (int32_t i = 0; i != n; ++i) {
+      DecodeStream(reinterpret_cast<OnlineStreamRknn *>(ss[i]));
+    }
+  }
+
+  OnlineRecognizerResult GetResult(OnlineStream *s) const override {
+    OnlineCtcDecoderResult decoder_result = s->GetCtcResult();
+
+    // TODO(fangjun): Remember to change these constants if needed
+    int32_t frame_shift_ms = 10;
+    int32_t subsampling_factor = 4;
+    auto r =
+        ConvertCtc(decoder_result, sym_, frame_shift_ms, subsampling_factor,
+                   s->GetCurrentSegment(), s->GetNumFramesSinceStart());
+    r.text = ApplyInverseTextNormalization(r.text);
+    return r;
+  }
+
+  bool IsEndpoint(OnlineStream *s) const override {
+    if (!config_.enable_endpoint) {
+      return false;
+    }
+
+    int32_t num_processed_frames = s->GetNumProcessedFrames();
+
+    // frame shift is 10 milliseconds
+    float frame_shift_in_seconds = 0.01;
+
+    // subsampling factor is 4
+    int32_t trailing_silence_frames = s->GetCtcResult().num_trailing_blanks * 4;
+
+    return endpoint_.IsEndpoint(num_processed_frames, trailing_silence_frames,
+                                frame_shift_in_seconds);
+  }
+
+  void Reset(OnlineStream *s) const override {
+    // segment is incremented only when the last
+    // result is not empty
+    const auto &r = s->GetCtcResult();
+    if (!r.tokens.empty()) {
+      s->GetCurrentSegment() += 1;
+    }
+
+    // clear result
+    s->SetCtcResult({});
+
+    // clear states
+    reinterpret_cast<OnlineStreamRknn *>(s)->SetZipformerEncoderStates(
+        model_->GetInitStates());
+
+    s->GetFasterDecoderProcessedFrames() = 0;
+
+    // Note: We only update counters. The underlying audio samples
+    // are not discarded.
+    s->Reset();
+  }
+
+ private:
+  void InitDecoder() {
+    if (!sym_.Contains("<blk>") && !sym_.Contains("<eps>") &&
+        !sym_.Contains("<blank>")) {
+      SHERPA_ONNX_LOGE(
+          "We expect that tokens.txt contains "
+          "the symbol <blk> or <eps> or <blank> and its ID.");
+      exit(-1);
+    }
+
+    int32_t blank_id = 0;
+    if (sym_.Contains("<blk>")) {
+      blank_id = sym_["<blk>"];
+    } else if (sym_.Contains("<eps>")) {
+      // for tdnn models of the yesno recipe from icefall
+      blank_id = sym_["<eps>"];
+    } else if (sym_.Contains("<blank>")) {
+      // for WeNet CTC models
+      blank_id = sym_["<blank>"];
+    }
+
+    if (!config_.ctc_fst_decoder_config.graph.empty()) {
+      decoder_ = std::make_unique<OnlineCtcFstDecoder>(
+          config_.ctc_fst_decoder_config, blank_id);
+    } else if (config_.decoding_method == "greedy_search") {
+      decoder_ = std::make_unique<OnlineCtcGreedySearchDecoder>(blank_id);
+    } else {
+      SHERPA_ONNX_LOGE(
+          "Unsupported decoding method: %s for streaming CTC models",
+          config_.decoding_method.c_str());
+      exit(-1);
+    }
+  }
+
+  void DecodeStream(OnlineStreamRknn *s) const {
+    int32_t chunk_size = model_->ChunkSize();
+    int32_t chunk_shift = model_->ChunkShift();
+
+    int32_t feat_dim = s->FeatureDim();
+
+    const auto num_processed_frames = s->GetNumProcessedFrames();
+    std::vector<float> features =
+        s->GetFrames(num_processed_frames, chunk_size);
+    s->GetNumProcessedFrames() += chunk_shift;
+
+    auto &states = s->GetZipformerEncoderStates();
+    auto p = model_->Run(features, std::move(states));
+    states = std::move(p.second);
+
+    std::vector<OnlineCtcDecoderResult> results(1);
+    results[0] = std::move(s->GetCtcResult());
+
+    auto attr = model_->GetOutAttr();
+
+    decoder_->Decode(p.first.data(), attr.dims[0], attr.dims[1], attr.dims[2],
+                     &results, reinterpret_cast<OnlineStream **>(&s), 1);
+    s->SetCtcResult(results[0]);
+  }
+
+ private:
+  OnlineRecognizerConfig config_;
+  std::unique_ptr<OnlineZipformerCtcModelRknn> model_;
+  std::unique_ptr<OnlineCtcDecoder> decoder_;
+  SymbolTable sym_;
+  Endpoint endpoint_;
+};
+
+}  // namespace sherpa_onnx
+
+#endif  // SHERPA_ONNX_CSRC_RKNN_ONLINE_RECOGNIZER_CTC_RKNN_IMPL_H_
diff --git a/sherpa-onnx/csrc/rknn/online-zipformer-ctc-model-rknn.cc b/sherpa-onnx/csrc/rknn/online-zipformer-ctc-model-rknn.cc
new file mode 100644
index 00000000..52a7b2ba
--- /dev/null
+++ b/sherpa-onnx/csrc/rknn/online-zipformer-ctc-model-rknn.cc
@@ -0,0 +1,390 @@
+// sherpa-onnx/csrc/rknn/online-zipformer-ctc-model-rknn.cc
+//
+// Copyright (c)  2025  Xiaomi Corporation
+
+#include "sherpa-onnx/csrc/rknn/online-zipformer-ctc-model-rknn.h"
+
+#include <memory>
+#include <sstream>
+#include <string>
+#include <unordered_map>
+#include <utility>
+#include <vector>
+
+#if __ANDROID_API__ >= 9
+#include "android/asset_manager.h"
+#include "android/asset_manager_jni.h"
+#endif
+
+#if __OHOS__
+#include "rawfile/raw_file_manager.h"
+#endif
+
+#include "sherpa-onnx/csrc/file-utils.h"
+#include "sherpa-onnx/csrc/rknn/macros.h"
+#include "sherpa-onnx/csrc/rknn/utils.h"
+#include "sherpa-onnx/csrc/text-utils.h"
+
+namespace sherpa_onnx {
+
+class OnlineZipformerCtcModelRknn::Impl {
+ public:
+  ~Impl() {
+    auto ret = rknn_destroy(ctx_);
+    if (ret != RKNN_SUCC) {
+      SHERPA_ONNX_LOGE("Failed to destroy the context");
+    }
+  }
+
+  explicit Impl(const OnlineModelConfig &config) : config_(config) {
+    {
+      auto buf = ReadFile(config.zipformer2_ctc.model);
+      Init(buf.data(), buf.size());
+    }
+
+    int32_t ret = RKNN_SUCC;
+    switch (config_.num_threads) {
+      case 1:
+        ret = rknn_set_core_mask(ctx_, RKNN_NPU_CORE_AUTO);
+        break;
+      case 0:
+        ret = rknn_set_core_mask(ctx_, RKNN_NPU_CORE_0);
+        break;
+      case -1:
+        ret = rknn_set_core_mask(ctx_, RKNN_NPU_CORE_1);
+        break;
+      case -2:
+        ret = rknn_set_core_mask(ctx_, RKNN_NPU_CORE_2);
+        break;
+      case -3:
+        ret = rknn_set_core_mask(ctx_, RKNN_NPU_CORE_0_1);
+        break;
+      case -4:
+        ret = rknn_set_core_mask(ctx_, RKNN_NPU_CORE_0_1_2);
+        break;
+      default:
+        SHERPA_ONNX_LOGE(
+            "Valid num_threads for rk npu is 1 (auto), 0 (core 0), -1 (core "
+            "1), -2 (core 2), -3 (core 0_1), -4 (core 0_1_2). Given: %d",
+            config_.num_threads);
+        break;
+    }
+    if (ret != RKNN_SUCC) {
+      SHERPA_ONNX_LOGE(
+          "Failed to select npu core to run the model (You can ignore it if "
+          "you "
+          "are not using RK3588.");
+    }
+  }
+
+  // TODO(fangjun): Support Android
+
+  std::vector<std::vector<uint8_t>> GetInitStates() const {
+    // input_attrs_[0] is for the feature
+    // input_attrs_[1:] is for states
+    // so we use -1 here
+    std::vector<std::vector<uint8_t>> states(input_attrs_.size() - 1);
+
+    int32_t i = -1;
+    for (auto &attr : input_attrs_) {
+      i += 1;
+      if (i == 0) {
+        // skip processing the attr for features.
+        continue;
+      }
+
+      if (attr.type == RKNN_TENSOR_FLOAT16) {
+        states[i - 1].resize(attr.n_elems * sizeof(float));
+      } else if (attr.type == RKNN_TENSOR_INT64) {
+        states[i - 1].resize(attr.n_elems * sizeof(int64_t));
+      } else {
+        SHERPA_ONNX_LOGE("Unsupported tensor type: %d, %s", attr.type,
+                         get_type_string(attr.type));
+        SHERPA_ONNX_EXIT(-1);
+      }
+    }
+
+    return states;
+  }
+
+  std::pair<std::vector<float>, std::vector<std::vector<uint8_t>>> Run(
+      std::vector<float> features,
+      std::vector<std::vector<uint8_t>> states) const {
+    std::vector<rknn_input> inputs(input_attrs_.size());
+
+    for (int32_t i = 0; i < static_cast<int32_t>(inputs.size()); ++i) {
+      auto &input = inputs[i];
+      auto &attr = input_attrs_[i];
+      input.index = attr.index;
+
+      if (attr.type == RKNN_TENSOR_FLOAT16) {
+        input.type = RKNN_TENSOR_FLOAT32;
+      } else if (attr.type == RKNN_TENSOR_INT64) {
+        input.type = RKNN_TENSOR_INT64;
+      } else {
+        SHERPA_ONNX_LOGE("Unsupported tensor type %d, %s", attr.type,
+                         get_type_string(attr.type));
+        SHERPA_ONNX_EXIT(-1);
+      }
+
+      input.fmt = attr.fmt;
+      if (i == 0) {
+        input.buf = reinterpret_cast<void *>(features.data());
+        input.size = features.size() * sizeof(float);
+      } else {
+        input.buf = reinterpret_cast<void *>(states[i - 1].data());
+        input.size = states[i - 1].size();
+      }
+    }
+
+    std::vector<float> out(output_attrs_[0].n_elems);
+
+    // Note(fangjun): We can reuse the memory from input argument `states`
+    // auto next_states = GetInitStates();
+    auto &next_states = states;
+
+    std::vector<rknn_output> outputs(output_attrs_.size());
+    for (int32_t i = 0; i < outputs.size(); ++i) {
+      auto &output = outputs[i];
+      auto &attr = output_attrs_[i];
+      output.index = attr.index;
+      output.is_prealloc = 1;
+
+      if (attr.type == RKNN_TENSOR_FLOAT16) {
+        output.want_float = 1;
+      } else if (attr.type == RKNN_TENSOR_INT64) {
+        output.want_float = 0;
+      } else {
+        SHERPA_ONNX_LOGE("Unsupported tensor type %d, %s", attr.type,
+                         get_type_string(attr.type));
+        SHERPA_ONNX_EXIT(-1);
+      }
+
+      if (i == 0) {
+        output.size = out.size() * sizeof(float);
+        output.buf = reinterpret_cast<void *>(out.data());
+      } else {
+        output.size = next_states[i - 1].size();
+        output.buf = reinterpret_cast<void *>(next_states[i - 1].data());
+      }
+    }
+
+    auto ret = rknn_inputs_set(ctx_, inputs.size(), inputs.data());
+    SHERPA_ONNX_RKNN_CHECK(ret, "Failed to set inputs");
+
+    ret = rknn_run(ctx_, nullptr);
+    SHERPA_ONNX_RKNN_CHECK(ret, "Failed to run the model");
+
+    ret = rknn_outputs_get(ctx_, outputs.size(), outputs.data(), nullptr);
+    SHERPA_ONNX_RKNN_CHECK(ret, "Failed to get model output");
+
+    for (int32_t i = 0; i < next_states.size(); ++i) {
+      const auto &attr = input_attrs_[i + 1];
+      if (attr.n_dims == 4) {
+        // TODO(fangjun): The transpose is copied from
+        // https://github.com/airockchip/rknn_model_zoo/blob/main/examples/zipformer/cpp/process.cc#L22
+        // I don't understand why we need to do that.
+        std::vector<uint8_t> dst(next_states[i].size());
+        int32_t n = attr.dims[0];
+        int32_t h = attr.dims[1];
+        int32_t w = attr.dims[2];
+        int32_t c = attr.dims[3];
+        ConvertNCHWtoNHWC(
+            reinterpret_cast<const float *>(next_states[i].data()), n, c, h, w,
+            reinterpret_cast<float *>(dst.data()));
+        next_states[i] = std::move(dst);
+      }
+    }
+
+    return {std::move(out), std::move(next_states)};
+  }
+
+  int32_t ChunkSize() const { return T_; }
+
+  int32_t ChunkShift() const { return decode_chunk_len_; }
+
+  int32_t VocabSize() const { return vocab_size_; }
+
+  rknn_tensor_attr GetOutAttr() const { return output_attrs_[0]; }
+
+ private:
+  void Init(void *model_data, size_t model_data_length) {
+    auto ret = rknn_init(&ctx_, model_data, model_data_length, 0, nullptr);
+    SHERPA_ONNX_RKNN_CHECK(ret, "Failed to init model '%s'",
+                           config_.zipformer2_ctc.model.c_str());
+
+    if (config_.debug) {
+      rknn_sdk_version v;
+      ret = rknn_query(ctx_, RKNN_QUERY_SDK_VERSION, &v, sizeof(v));
+      SHERPA_ONNX_RKNN_CHECK(ret, "Failed to get rknn sdk version");
+
+      SHERPA_ONNX_LOGE("sdk api version: %s, driver version: %s", v.api_version,
+                       v.drv_version);
+    }
+
+    rknn_input_output_num io_num;
+    ret = rknn_query(ctx_, RKNN_QUERY_IN_OUT_NUM, &io_num, sizeof(io_num));
+    SHERPA_ONNX_RKNN_CHECK(ret, "Failed to get I/O information for the model");
+
+    if (config_.debug) {
+      SHERPA_ONNX_LOGE("model: %d inputs, %d outputs",
+                       static_cast<int32_t>(io_num.n_input),
+                       static_cast<int32_t>(io_num.n_output));
+    }
+
+    input_attrs_.resize(io_num.n_input);
+    output_attrs_.resize(io_num.n_output);
+
+    int32_t i = 0;
+    for (auto &attr : input_attrs_) {
+      memset(&attr, 0, sizeof(attr));
+      attr.index = i;
+      ret = rknn_query(ctx_, RKNN_QUERY_INPUT_ATTR, &attr, sizeof(attr));
+      SHERPA_ONNX_RKNN_CHECK(ret, "Failed to get attr for model input %d", i);
+      i += 1;
+    }
+
+    if (config_.debug) {
+      std::ostringstream os;
+      std::string sep;
+      for (auto &attr : input_attrs_) {
+        os << sep << ToString(attr);
+        sep = "\n";
+      }
+      SHERPA_ONNX_LOGE("\n----------Model inputs info----------\n%s",
+                       os.str().c_str());
+    }
+
+    i = 0;
+    for (auto &attr : output_attrs_) {
+      memset(&attr, 0, sizeof(attr));
+      attr.index = i;
+      ret = rknn_query(ctx_, RKNN_QUERY_OUTPUT_ATTR, &attr, sizeof(attr));
+      SHERPA_ONNX_RKNN_CHECK(ret, "Failed to get attr for model output %d", i);
+      i += 1;
+    }
+
+    if (config_.debug) {
+      std::ostringstream os;
+      std::string sep;
+      for (auto &attr : output_attrs_) {
+        os << sep << ToString(attr);
+        sep = "\n";
+      }
+      SHERPA_ONNX_LOGE("\n----------Model outputs info----------\n%s",
+                       os.str().c_str());
+    }
+
+    rknn_custom_string custom_string;
+    ret = rknn_query(ctx_, RKNN_QUERY_CUSTOM_STRING, &custom_string,
+                     sizeof(custom_string));
+    SHERPA_ONNX_RKNN_CHECK(ret, "Failed to read custom string from the model");
+    if (config_.debug) {
+      SHERPA_ONNX_LOGE("customs string: %s", custom_string.string);
+    }
+    auto meta = Parse(custom_string);
+
+    if (config_.debug) {
+      for (const auto &p : meta) {
+        SHERPA_ONNX_LOGE("%s: %s", p.first.c_str(), p.second.c_str());
+      }
+    }
+
+    if (meta.count("T")) {
+      T_ = atoi(meta.at("T").c_str());
+    }
+
+    if (meta.count("decode_chunk_len")) {
+      decode_chunk_len_ = atoi(meta.at("decode_chunk_len").c_str());
+    }
+
+    vocab_size_ = output_attrs_[0].dims[2];
+
+    if (config_.debug) {
+#if __OHOS__
+      SHERPA_ONNX_LOGE("T: %{public}d", T_);
+      SHERPA_ONNX_LOGE("decode_chunk_len_: %{public}d", decode_chunk_len_);
+      SHERPA_ONNX_LOGE("vocab_size: %{public}d", vocab_size);
+#else
+      SHERPA_ONNX_LOGE("T: %d", T_);
+      SHERPA_ONNX_LOGE("decode_chunk_len_: %d", decode_chunk_len_);
+      SHERPA_ONNX_LOGE("vocab_size: %d", vocab_size_);
+#endif
+    }
+
+    if (T_ == 0) {
+      SHERPA_ONNX_LOGE(
+          "Invalid T. Please use the script from icefall to export your model");
+      SHERPA_ONNX_EXIT(-1);
+    }
+
+    if (decode_chunk_len_ == 0) {
+      SHERPA_ONNX_LOGE(
+          "Invalid decode_chunk_len. Please use the script from icefall to "
+          "export your model");
+      SHERPA_ONNX_EXIT(-1);
+    }
+  }
+
+ private:
+  OnlineModelConfig config_;
+  rknn_context ctx_ = 0;
+
+  std::vector<rknn_tensor_attr> input_attrs_;
+  std::vector<rknn_tensor_attr> output_attrs_;
+
+  int32_t T_ = 0;
+  int32_t decode_chunk_len_ = 0;
+  int32_t vocab_size_ = 0;
+};
+
+OnlineZipformerCtcModelRknn::~OnlineZipformerCtcModelRknn() = default;
+
+OnlineZipformerCtcModelRknn::OnlineZipformerCtcModelRknn(
+    const OnlineModelConfig &config)
+    : impl_(std::make_unique<Impl>(config)) {}
+
+template <typename Manager>
+OnlineZipformerCtcModelRknn::OnlineZipformerCtcModelRknn(
+    Manager *mgr, const OnlineModelConfig &config)
+    : impl_(std::make_unique<OnlineZipformerCtcModelRknn>(mgr, config)) {}
+
+std::vector<std::vector<uint8_t>> OnlineZipformerCtcModelRknn::GetInitStates()
+    const {
+  return impl_->GetInitStates();
+}
+
+std::pair<std::vector<float>, std::vector<std::vector<uint8_t>>>
+OnlineZipformerCtcModelRknn::Run(
+    std::vector<float> features,
+    std::vector<std::vector<uint8_t>> states) const {
+  return impl_->Run(std::move(features), std::move(states));
+}
+
+int32_t OnlineZipformerCtcModelRknn::ChunkSize() const {
+  return impl_->ChunkSize();
+}
+
+int32_t OnlineZipformerCtcModelRknn::ChunkShift() const {
+  return impl_->ChunkShift();
+}
+
+int32_t OnlineZipformerCtcModelRknn::VocabSize() const {
+  return impl_->VocabSize();
+}
+
+rknn_tensor_attr OnlineZipformerCtcModelRknn::GetOutAttr() const {
+  return impl_->GetOutAttr();
+}
+
+#if __ANDROID_API__ >= 9
+template OnlineZipformerCtcModelRknn::OnlineZipformerCtcModelRknn(
+    AAssetManager *mgr, const OnlineModelConfig &config);
+#endif
+
+#if __OHOS__
+template OnlineZipformerCtcModelRknn::OnlineZipformerCtcModelRknn(
+    NativeResourceManager *mgr, const OnlineModelConfig &config);
+#endif
+
+}  // namespace sherpa_onnx
diff --git a/sherpa-onnx/csrc/rknn/online-zipformer-ctc-model-rknn.h b/sherpa-onnx/csrc/rknn/online-zipformer-ctc-model-rknn.h
new file mode 100644
index 00000000..49242a4e
--- /dev/null
+++ b/sherpa-onnx/csrc/rknn/online-zipformer-ctc-model-rknn.h
@@ -0,0 +1,46 @@
+// sherpa-onnx/csrc/rknn/online-zipformer-ctc-model-rknn.h
+//
+// Copyright (c)  2025  Xiaomi Corporation
+#ifndef SHERPA_ONNX_CSRC_RKNN_ONLINE_ZIPFORMER_CTC_MODEL_RKNN_H_
+#define SHERPA_ONNX_CSRC_RKNN_ONLINE_ZIPFORMER_CTC_MODEL_RKNN_H_
+
+#include <memory>
+#include <utility>
+#include <vector>
+
+#include "rknn_api.h"  // NOLINT
+#include "sherpa-onnx/csrc/online-model-config.h"
+
+namespace sherpa_onnx {
+
+class OnlineZipformerCtcModelRknn {
+ public:
+  ~OnlineZipformerCtcModelRknn();
+
+  explicit OnlineZipformerCtcModelRknn(const OnlineModelConfig &config);
+
+  template <typename Manager>
+  OnlineZipformerCtcModelRknn(Manager *mgr, const OnlineModelConfig &config);
+
+  std::vector<std::vector<uint8_t>> GetInitStates() const;
+
+  std::pair<std::vector<float>, std::vector<std::vector<uint8_t>>> Run(
+      std::vector<float> features,
+      std::vector<std::vector<uint8_t>> states) const;
+
+  int32_t ChunkSize() const;
+
+  int32_t ChunkShift() const;
+
+  int32_t VocabSize() const;
+
+  rknn_tensor_attr GetOutAttr() const;
+
+ private:
+  class Impl;
+  std::unique_ptr<Impl> impl_;
+};
+
+}  // namespace sherpa_onnx
+
+#endif  // SHERPA_ONNX_CSRC_RKNN_ONLINE_ZIPFORMER_CTC_MODEL_RKNN_H_
diff --git a/sherpa-onnx/csrc/rknn/online-zipformer-transducer-model-rknn.cc b/sherpa-onnx/csrc/rknn/online-zipformer-transducer-model-rknn.cc
index 67a81fdf..7b6d505d 100644
--- a/sherpa-onnx/csrc/rknn/online-zipformer-transducer-model-rknn.cc
+++ b/sherpa-onnx/csrc/rknn/online-zipformer-transducer-model-rknn.cc
@@ -1,6 +1,6 @@
 // sherpa-onnx/csrc/rknn/online-zipformer-transducer-model-rknn.cc
 //
-// Copyright (c)  2023  Xiaomi Corporation
+// Copyright (c)  2025  Xiaomi Corporation
 
 #include "sherpa-onnx/csrc/rknn/online-zipformer-transducer-model-rknn.h"
 
@@ -22,68 +22,11 @@
 
 #include "sherpa-onnx/csrc/file-utils.h"
 #include "sherpa-onnx/csrc/rknn/macros.h"
+#include "sherpa-onnx/csrc/rknn/utils.h"
 #include "sherpa-onnx/csrc/text-utils.h"
 
 namespace sherpa_onnx {
 
-// chw -> hwc
-static void Transpose(const float *src, int32_t n, int32_t channel,
-                      int32_t height, int32_t width, float *dst) {
-  for (int32_t i = 0; i < n; ++i) {
-    for (int32_t h = 0; h < height; ++h) {
-      for (int32_t w = 0; w < width; ++w) {
-        for (int32_t c = 0; c < channel; ++c) {
-          // dst[h, w, c] = src[c, h, w]
-          dst[i * height * width * channel + h * width * channel + w * channel +
-              c] = src[i * height * width * channel + c * height * width +
-                       h * width + w];
-        }
-      }
-    }
-  }
-}
-
-static std::string ToString(const rknn_tensor_attr &attr) {
-  std::ostringstream os;
-  os << "{";
-  os << attr.index;
-  os << ", name: " << attr.name;
-  os << ", shape: (";
-  std::string sep;
-  for (int32_t i = 0; i < static_cast<int32_t>(attr.n_dims); ++i) {
-    os << sep << attr.dims[i];
-    sep = ",";
-  }
-  os << ")";
-  os << ", n_elems: " << attr.n_elems;
-  os << ", size: " << attr.size;
-  os << ", fmt: " << get_format_string(attr.fmt);
-  os << ", type: " << get_type_string(attr.type);
-  os << ", pass_through: " << (attr.pass_through ? "true" : "false");
-  os << "}";
-  return os.str();
-}
-
-static std::unordered_map<std::string, std::string> Parse(
-    const rknn_custom_string &custom_string) {
-  std::unordered_map<std::string, std::string> ans;
-  std::vector<std::string> fields;
-  SplitStringToVector(custom_string.string, ";", false, &fields);
-
-  std::vector<std::string> tmp;
-  for (const auto &f : fields) {
-    SplitStringToVector(f, "=", false, &tmp);
-    if (tmp.size() != 2) {
-      SHERPA_ONNX_LOGE("Invalid custom string %s for %s", custom_string.string,
-                       f.c_str());
-      SHERPA_ONNX_EXIT(-1);
-    }
-    ans[std::move(tmp[0])] = std::move(tmp[1]);
-  }
-
-  return ans;
-}
-
 class OnlineZipformerTransducerModelRknn::Impl {
  public:
   ~Impl() {
@@ -285,7 +228,7 @@ class OnlineZipformerTransducerModelRknn::Impl {
     for (int32_t i = 0; i < next_states.size(); ++i) {
       const auto &attr = encoder_input_attrs_[i + 1];
       if (attr.n_dims == 4) {
-        // TODO(fangjun): The transpose is copied from
+        // TODO(fangjun): The ConvertNCHWtoNHWC is copied from
         // https://github.com/airockchip/rknn_model_zoo/blob/main/examples/zipformer/cpp/process.cc#L22
         // I don't understand why we need to do that.
         std::vector<uint8_t> dst(next_states[i].size());
@@ -293,8 +236,9 @@ class OnlineZipformerTransducerModelRknn::Impl {
         int32_t h = attr.dims[1];
         int32_t w = attr.dims[2];
         int32_t c = attr.dims[3];
-        Transpose(reinterpret_cast<const float *>(next_states[i].data()), n, c,
-                  h, w, reinterpret_cast<float *>(dst.data()));
+        ConvertNCHWtoNHWC(
+            reinterpret_cast<const float *>(next_states[i].data()), n, c, h, w,
+            reinterpret_cast<float *>(dst.data()));
         next_states[i] = std::move(dst);
       }
     }
@@ -527,11 +471,9 @@ class OnlineZipformerTransducerModelRknn::Impl {
 #if __OHOS__
       SHERPA_ONNX_LOGE("T: %{public}d", T_);
       SHERPA_ONNX_LOGE("decode_chunk_len_: %{public}d", decode_chunk_len_);
-      SHERPA_ONNX_LOGE("context_size: %{public}d", context_size_);
 #else
       SHERPA_ONNX_LOGE("T: %d", T_);
       SHERPA_ONNX_LOGE("decode_chunk_len_: %d", decode_chunk_len_);
-      SHERPA_ONNX_LOGE("context_size: %d", context_size_);
 #endif
     }
   }
@@ -597,6 +539,11 @@ class OnlineZipformerTransducerModelRknn::Impl {
       SHERPA_ONNX_EXIT(-1);
     }
 
+    context_size_ = decoder_input_attrs_[0].dims[1];
+    if (config_.debug) {
+      SHERPA_ONNX_LOGE("context_size: %d", context_size_);
+    }
+
     i = 0;
     for (auto &attr : decoder_output_attrs_) {
       memset(&attr, 0, sizeof(attr));
diff --git a/sherpa-onnx/csrc/rknn/online-zipformer-transducer-model-rknn.h b/sherpa-onnx/csrc/rknn/online-zipformer-transducer-model-rknn.h
index bc821afa..e99aaf98 100644
--- a/sherpa-onnx/csrc/rknn/online-zipformer-transducer-model-rknn.h
+++ b/sherpa-onnx/csrc/rknn/online-zipformer-transducer-model-rknn.h
@@ -14,8 +14,11 @@
 
 namespace sherpa_onnx {
 
-// this is for zipformer v1, i.e., the folder
-// pruned_transducer_statelss7_streaming from icefall
+// this is for zipformer v1 and v2, i.e., the folder
+// pruned_transducer_statelss7_streaming
+// and
+// zipformer
+// from icefall
 class OnlineZipformerTransducerModelRknn {
  public:
   ~OnlineZipformerTransducerModelRknn();
diff --git a/sherpa-onnx/csrc/rknn/utils.cc b/sherpa-onnx/csrc/rknn/utils.cc
new file mode 100644
index 00000000..e1581ed4
--- /dev/null
+++ b/sherpa-onnx/csrc/rknn/utils.cc
@@ -0,0 +1,73 @@
+// sherpa-onnx/csrc/utils.cc
+//
+// Copyright      2025  Xiaomi Corporation
+
+#include "sherpa-onnx/csrc/rknn/utils.h"
+
+#include <sstream>
+#include <unordered_map>
+#include <vector>
+
+#include "sherpa-onnx/csrc/macros.h"
+#include "sherpa-onnx/csrc/text-utils.h"
+
+namespace sherpa_onnx {
+
+void ConvertNCHWtoNHWC(const float *src, int32_t n, int32_t channel,
+                       int32_t height, int32_t width, float *dst) {
+  for (int32_t i = 0; i < n; ++i) {
+    for (int32_t h = 0; h < height; ++h) {
+      for (int32_t w = 0; w < width; ++w) {
+        for (int32_t c = 0; c < channel; ++c) {
+          // dst[h, w, c] = src[c, h, w]
+          dst[i * height * width * channel + h * width * channel + w * channel +
+              c] = src[i * height * width * channel + c * height * width +
+                       h * width + w];
+        }
+      }
+    }
+  }
+}
+
+std::string ToString(const rknn_tensor_attr &attr) {
+  std::ostringstream os;
+  os << "{";
+  os << attr.index;
+  os << ", name: " << attr.name;
+  os << ", shape: (";
+  std::string sep;
+  for (int32_t i = 0; i < static_cast<int32_t>(attr.n_dims); ++i) {
+    os << sep << attr.dims[i];
+    sep = ",";
+  }
+  os << ")";
+  os << ", n_elems: " << attr.n_elems;
+  os << ", size: " << attr.size;
+  os << ", fmt: " << get_format_string(attr.fmt);
+  os << ", type: " << get_type_string(attr.type);
+  os << ", pass_through: " << (attr.pass_through ? "true" : "false");
+  os << "}";
+  return os.str();
+}
+
+std::unordered_map<std::string, std::string> Parse(
+    const rknn_custom_string &custom_string) {
+  std::unordered_map<std::string, std::string> ans;
+  std::vector<std::string> fields;
+  SplitStringToVector(custom_string.string, ";", false, &fields);
+
+  std::vector<std::string> tmp;
+  for (const auto &f : fields) {
+    SplitStringToVector(f, "=", false, &tmp);
+    if (tmp.size() != 2) {
+      SHERPA_ONNX_LOGE("Invalid custom string %s for %s", custom_string.string,
+                       f.c_str());
+      SHERPA_ONNX_EXIT(-1);
+    }
+    ans[std::move(tmp[0])] = std::move(tmp[1]);
+  }
+
+  return ans;
+}
+
+}  // namespace sherpa_onnx
diff --git a/sherpa-onnx/csrc/rknn/utils.h b/sherpa-onnx/csrc/rknn/utils.h
new file mode 100644
index 00000000..077d3f65
--- /dev/null
+++ b/sherpa-onnx/csrc/rknn/utils.h
@@ -0,0 +1,23 @@
+// sherpa-onnx/csrc/utils.h
+//
+// Copyright      2025  Xiaomi Corporation
+
+#ifndef SHERPA_ONNX_CSRC_RKNN_UTILS_H_
+#define SHERPA_ONNX_CSRC_RKNN_UTILS_H_
+
+#include <string>
+#include <unordered_map>
+
+#include "rknn_api.h"  // NOLINT
+
+namespace sherpa_onnx {
+void ConvertNCHWtoNHWC(const float *src, int32_t n, int32_t channel,
+                       int32_t height, int32_t width, float *dst);
+
+std::string ToString(const rknn_tensor_attr &attr);
+
+std::unordered_map<std::string, std::string> Parse(
+    const rknn_custom_string &custom_string);
+}  // namespace sherpa_onnx
+
+#endif  // SHERPA_ONNX_CSRC_RKNN_UTILS_H_
diff --git a/sherpa-onnx/csrc/sherpa-onnx.cc b/sherpa-onnx/csrc/sherpa-onnx.cc
index 7f0db215..3af4f412 100644
--- a/sherpa-onnx/csrc/sherpa-onnx.cc
+++ b/sherpa-onnx/csrc/sherpa-onnx.cc
@@ -83,6 +83,7 @@ for a list of pre-trained models to download.
   po.Read(argc, argv);
   if (po.NumArgs() < 1) {
     po.PrintUsage();
+    fprintf(stderr, "Error! Please provide at lease 1 wav file\n");
     exit(EXIT_FAILURE);
   }