Kernel module for CH341 USB-I2C adaptor

zeirix · February 27, 2024, 10:05am

Hello everybody,

can anybody tell me, how to use a CH341 USB-I2C adaptor in dietpi?
I’m using DietPi v9.1.1 on a device model RPi B (armv6l).

I’ve already modprobed the i2c-dev and ch341 modules before connecting the adaptor to one of the USB ports, but in the /dev tree only the internal i2c-1 is showing up.

The adaptor itself shows up in the debug messages:

[855727.220757] usb 1-1.3.1: new full-speed USB device number 12 using dwc_otg
[855727.353170] usb 1-1.3.1: New USB device found, idVendor=1a86, idProduct=5512, bcdDevice= 3.04
[855727.353252] usb 1-1.3.1: New USB device strings: Mfr=0, Product=0, SerialNumber=0

The adaptor itself is working at another computer with another distro. The USB port at the Pi is OK, too.

Thanks a lot!

WarHawk · February 28, 2024, 3:41am

is it plugged into the otg port?
Might be able to build it with this?

There is also this

github.com

gschorcht/i2c-ch341-usb/blob/master/README.md

# CH341A USB to I2C and GPIO Linux kernel driver

The driver can be used with **CH341A** USB to UART/I2C/SPI adapter boards to connect I2C devices to a Linux host.

Additionally, CH341A data pins that are not used for synchronous serial interfaces can be configured as **GPIO** pins. The driver can generate **software interrupts** for all input pins. **One input** pin can be connected with the CH341A interrupt pin to generate **hardware interrupts**. 

The I2C interface driver was initially derived from [CH341 I2C driver from Tse Lun Bien](https://github.com/allanbian1017/i2c-ch341-usb.git) and extended by GPIO and interrupt handling capabilities.

## I2C interface limitations

By default, the driver uses the standard I2C bus speed of **100 kbps**. I2C bus speeds of 20 kbps, **400 kbps** and 750 kbps are also available. 

Currently only basic I2C read and write functions (**`I2C_FUNC_I2C`**) are supported natively. However, SMBus protocols are emulated (**`I2C_FUNC_SMBUS_EMUL`**) with the exception of SMBus Block Read (`I2C_FUNC_SMBUS_READ_BLOCK_DATA`) and SMBus Block Process Call (`I2C_FUNC_SMBUS_BLOCK_PROC_CALL`).

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 driver supports only I2C messages with a **maximum data size of 26 bytes**.

## GPIO limitations

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zeirix · February 28, 2024, 8:43pm

Hi WarHawk,

I’ve made and installed the mentioned driver.
With the ch34x module loaded, the adaptor now seems to be recognized correctly:

[979592.599750] usbcore: registered new interface driver ch34x
[979592.611057] usbserial: USB Serial support registered for ch34x

It also seems to use usbserial

lsmod

Module Size Used by
ch34x 8850 0
i2c_dev 6915 0
usbserial 30953 1 ch34x
…

But, in the device tree nothing changed, the only i2c device is the internal i2c-1 .
Do I need a udev rule for this?

WarHawk · February 29, 2024, 3:25am

unsure…but go to the “Linux” section here…see if the commands help
https://learn.sparkfun.com/tutorials/how-to-install-ch340-drivers/all
You might have to add the user to the dialout group then reboot…

does lsusb show the device mapped to a USB port/device?

Other than that…I’m at a loss

markbirss · July 29, 2024, 6:52pm

system · January 25, 2025, 6:52pm

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