This is a Rust embedded-hal implementation for the ch341 chips, such as the inexpensive ch341t-dongle (1.31 USD as of Nov 2022).
This enables development of embedded device drivers on a PC without the use of a microcontroller, using the same hal trait definitions. The ch341 devices interface with a PC via USB, and provide a synchronous serial engine to interface with I2C embedded devices.
This library uses libusb internally and thus does not rely on any device-specific kernel driver. The implementation is influenced by the out-of-tree linux driver i2c-ch341-usb.
By default, the library uses the standard I2C bus speed of 100 kbps. I2C bus speeds of 20 kbps, 400 kbps and 750 kbps are also available.
The CH341A only supports 7 bit addressing.
Due of the limited CH341A USB endpoint buffer size of 32 byte that is used for I2C data as well as adapter in-band signaling, the library supports only I2C messages with a maximum data size of 26 bytes.
ch341 chips can alternatively be configured as UART devices or as I2C adapters (which is what we want).
On the module shown, this is controlled via a jumper. Make sure your jumper is set to I2C mode before
plugging the device. It should enumerate like so in sudo lsusb:
Bus 001 Device 029: ID 1a86:5512 QinHeng Electronics CH341 in EPP/MEM/I2C mode, EPP/I2C adapter
See full lsusb output
You need to have libusb libraries installed in your system (e.g sudo apt install libusb-1.0-0 libusb-1.0-0-dev)
In order to avoid running your code as root to gain access to the ch341 device in Linux, you may want to create a uded rule file e.g /etc/udev/rules.d/99-ch341.rules with the following contents:
SUBSYSTEM=="usb", ATTRS{idVendor}=="1a86", ATTRS{idProduct}=="5512", MODE:="0666"
And plug / unplug the device for the udev settings to apply.
Checkout the examples folder for code examples, build the examples using cargo build --examples