The latest articles on DEV Community by Ishu1519 (@ishu1519). https://dev.to/ishu1519 https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.us-east-2.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F4079020%2F2bc39360-8979-4d45-9bba-34ffa687952f.png https://dev.to/ishu1519 en Ishu1519 Sun, 16 Aug 2026 06:42:27 +0000 https://dev.to/ishu1519/i-built-an-esp32-s3-ch32v003-swio-programmer-51p8 https://dev.to/ishu1519/i-built-an-esp32-s3-ch32v003-swio-programmer-51p8 <p>I wanted to see if an ESP32-S3 could be used as a programmer for the WCH CH32V003 instead of using a dedicated WCH-Link.</p> <p>The final setup is:</p> <p>PC → ESP32-S3 → SWIO → CH32V003</p> <p>The ESP32-S3 handles the timing-sensitive SWIO communication and the CH32 debug/DMI interface. On top of that I implemented target detection, memory access, flash unlock, page erase, programming, read-back verification and reset/run.</p> <h2> Hardware </h2> <ul> <li>ESP32-S3 N8R2</li> <li>CH32V003A4M6 (SOP-16)</li> <li>4.7kΩ–10kΩ SWIO pull-up</li> <li>CP6208 motor driver</li> <li>Small DC motor</li> <li>3.7V Li-ion battery</li> <li>Breadboard</li> </ul> <p>Important connections:</p> <ul> <li>ESP32-S3 GPIO10 → CH32V003 SWIO</li> <li>ESP32-S3 3.3V → CH32V003 VDD</li> <li>Common GND</li> <li>External pull-up on SWIO</li> <li>CH32V003 PC4 → CP6208 control input</li> </ul> <h2> The software stack </h2> <p>The programmer is split into several layers:</p> <div class="highlight js-code-highlight"> <pre class="highlight plaintext"><code> text PC │ │ Python host tool ▼ ESP32-S3 │ │ SWIO ▼ WCH DMI │ ▼ CH32V003 debug module │ ▼ Abstract commands / program buffer │ ▼ Flash controller The ESP32-S3 is doing the SWIO timing directly rather than relying on a separate programmer IC. I used existing open-source CH32/SWIO implementations as references, particularly CNLohr's CH32V003 work and BlueSyncLine's SWIO implementation. Getting SWIO working The first versions did not work. One of the early failures was: SWIO sync: FAILED DMCFGR = 0xFFFFFFFF I had to work through the SWIO startup sequence, timing, receive behavior and physical wiring before getting reliable target responses. Once it was working, the programmer reported: SWIO sync: OK DMI communication: OK Target detect: OK CH32 ID = 0x0713BB91 Target memory read: OK That gave me a stable base for the flash implementation. Flash programming I then added the flash controller operations: flash unlock 64-byte page erase fast page programming read-back verification target reset/run One useful milestone was observing the flash lock transition: FLASH_CTLR before unlock: 0x00008080 FLASH_CTLR after unlock: 0x00000200 After that I tested programming and verification using deterministic data. The programmer was able to write data to the CH32V003 flash and read it back with zero mismatches. The first real application test For the first application I built a tiny bare-metal CH32V003 firmware that drives PC4. Instead of an LED, I used a CP6208 motor driver and a small DC motor. The first attempt failed even though the firmware had been programmed and verified. The CH32 was actually running and PC4 was at about 3.3V. The problem turned out to be the CP6208 input state: the second input was HIGH instead of LOW. That put the driver into the wrong state. After grounding that input, the motor started. That was probably the most useful debugging lesson from the entire project: the programming path can be completely correct while the final hardware application is still wrong. Final host workflow The programmer now has a Python command-line tool. For example: python tools/flash_tool.py --port COM10 --bin firmware/ch32_blink/blink.bin --addr 0x08000000 --reset The final test performed on real hardware was: Target detect: OK Programming: OK Verification: OK Reset/run: OK The programmed CH32V003 then executed the application and drove the motor. Source code GitHub: https://github.com/Ishu1519/esp32s3-ch32-programmer The repository includes: ESP32-S3 programmer firmware CH32V003 target example Python host flasher hardware documentation SWIO/DMI documentation build instructions What's next The current implementation is focused on the CH32V003. The next interesting question is how far the same ESP32-S3 transport can be extended to other WCH RISC-V devices, and whether more debugging functionality can be added beyond programming.  # I Built an ESP32-S3 CH32V003 SWIO Programmer    </code></pre> </div> esp32 embedded hardware riscv