diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml
index 71fde7d..d325329 100644
--- a/.github/workflows/build.yaml
+++ b/.github/workflows/build.yaml
@@ -133,6 +133,49 @@ jobs:
         path: dist
 
 
+  build-riscv:
+    runs-on: ubuntu-24.04
+    env:
+      MPY_DIR: ./micropython
+      MICROPYTHON_BIN: ./micropython/ports/unix/build-nomodules/micropython
+    steps:
+    - uses: actions/checkout@v4
+      with:
+        submodules: true
+    - name: Install OS dependencies
+      run: sudo add-apt-repository universe
+    - uses: actions/setup-python@v5
+      with:
+        python-version: '3.10'
+    - uses: actions/checkout@v4
+      with:
+        repository: jonnor/micropython
+        path: micropython
+        ref: v1.25.0-armv6m-abs-relocations
+    - name: Install Python dependencies
+      run: pip install -r requirements.txt
+
+    - name: Setup MicroPython ESP32
+      working-directory: micropython
+      run: |
+        source tools/ci.sh && ci_esp32_idf_setup && ci_gcc_riscv_setup
+        make -C mpy-cross
+    - name: Setup submodules esp32
+      working-directory: micropython/ports/esp32
+      run: source ../../esp-idf/export.sh && make submodules
+    - name: Build custom firmware with extmod, ESP32
+      run: |
+        source micropython/esp-idf/export.sh && pip install -r requirements.txt
+        echo make extmod PORT=esp32 BOARD=ESP32_GENERIC_C6
+    - name: Build nadmod xtensawin
+      run: source micropython/esp-idf/export.sh && pip install -r requirements.txt && make dist ARCH=rv32imc V=1
+    - name: Archive dist artifacts
+      uses: actions/upload-artifact@v4
+      with:
+        name: emlearn-micropython-build-riscv
+        path: dist
+
+
   build-macos:
     runs-on: macos-latest
     env:
@@ -178,7 +221,7 @@ jobs:
   deploy-pages:
     permissions:
       contents: write
-    needs: [build-linux, build-arm, build-esp32, build-macos]
+    needs: [build-linux, build-arm, build-esp32, build-macos, build-riscv]
     runs-on: ubuntu-latest
     
     steps:
diff --git a/README.md b/README.md
index 0237bd2..e809343 100644
--- a/README.md
+++ b/README.md
@@ -80,16 +80,34 @@ git clone https://github.com/emlearn/emlearn-micropython
 ```
 
 #### Prerequisites
-These come in addition to the prequisites described above.
 
-Make sure you have the dependencies needed to build for your platform.
-See [MicroPython: Building native modules](https://docs.micropython.org/en/latest/develop/natmod.html).
+You will need to have **Python 3.10+ or later** already installed.
 
-We assume that micropython is installed in the same place as this repository.
+We assume that **micropython** git repository available.
+It is assumed to be at the same level as this repository in the file system.
 If using another location, adjust `MPY_DIR` accordingly.
-
 You should be using MicroPython 1.25 (or newer).
 
+Make sure you have the **build toolchain** needed for your platform.
+See [MicroPython: Building native modules](https://docs.micropython.org/en/latest/develop/natmod.html),
+and the documentation for the MicroPython port/architecture of interest.
+
+#### Download dependencies
+
+Fetch git submodules
+
+```
+git submodule update --init
+```
+
+Recommend using a Python virtual environment.
+
+Install Python packages
+```
+pip install -r requirements.txt
+```
+
+
 #### Build
 
 Build the .mpy native module
diff --git a/requirements.txt b/requirements.txt
index 3a89384..9c11383 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,3 +2,4 @@ emlearn>=0.21.2
 scikit-learn>=1.0.0
 ar>=1.0.0
 pyelftools>=0.31
+setuptools>=71.0.0
diff --git a/src/emlearn_iir_q15/iir_filter.c b/src/emlearn_iir_q15/iir_filter.c
index a918029..382fa2d 100644
--- a/src/emlearn_iir_q15/iir_filter.c
+++ b/src/emlearn_iir_q15/iir_filter.c
@@ -5,8 +5,9 @@
 
 #include <string.h>
 
-// memset is used by some standard C constructs
-#if !defined(__linux__)
+// memset is used by some standard C constructs. Missing on some platforms, but not all...
+// Unfortunately cannot use weak symbols with mpy_ld
+#if !(defined(__linux__) || defined(__riscv__) || defined(__riscv))
 void *memcpy(void *dst, const void *src, size_t n) {
     return mp_fun_table.memmove_(dst, src, n);
 }