Asprogrammer+21013 May 2026
Windows does not natively support the CH341A in SPI mode correctly. You must replace the default driver with WinUSB or libusb using a tool called Zadig. If you have the wrong driver installed (e.g., a serial COM port driver), ASProgrammer will throw a 21013 error because it cannot claim the USB interface.
Using a multimeter, measure between pin 4 (GND) and pin 8 (VCC) on your SOIC8 chip. You should see either 3.3V or 5V depending on your programmer’s jumper. If you see 0V, your clip is misaligned or your CH341A is dead. If you see 5V on a 3.3V chip, stop immediately—you may have damaged the chip. You need a 3.3V adapter board (or modify the CH341A by cutting the 5V trace).
Download Zadig (version 2.8 or later). Ensure your CH341A is plugged in. asprogrammer+21013
Why WinUSB? Unlike libusb, WinUSB has better timeout handling, directly solving the 21013 sync errors.
| Feature | ASProgrammer+ 21013 | Official CH341A Software |
| :--- | :--- | :--- |
| OS Support | Windows 7, 8, 10, 11 (x86/x64) | Often fails on Windows 10+ |
| Driver | Uses libusbK or CH341PAR | Requires specific, often old drivers |
| Chip Detection | Robust JEDEC ID detection | Manual selection often required |
| File Size | Very small (< 1MB) | Often bloated with ads/bloatware |
| Source Code | Open Source | Closed Source | Windows does not natively support the CH341A in
| Feature | ASprogrammer | Flashrom (CLI) | | :--- | :--- | :--- | | Learning curve | Low (GUI) | High (command line) | | Chip auto-detect | Yes (partial) | Manual | | Visual hex editor | Built-in | None | | Verify after write | Yes | Yes (with flags) |
For quick board repairs, clicking a button is simply faster than typing sudo flashrom -p ch341a_spi -w bios.bin. Why WinUSB
Check these:
| Issue | Fix | |-------|-----| | Driver conflict with CH341SER (COM port) | Use Zadig to change to WinUSB | | Another program using the device (e.g., NeoProgrammer, Flashrom) | Close all other programming software | | USB power issue (especially with 1.8V chips) | Use external power or check voltage jumper on CH341A board | | Faulty CH341A clone | Some cheap clones have bad USB PID/VID – try different USB port or reinstall driver with Zadig |
