devnum numbering rule

[nidorhuang]

Hi,

Is there a way to determine the relationship between devnum and sysfs device?

I'm trying to write a linux python script to initialize multiple MCP2221A devices. I first checked the sysfs for some basic information such as the number of MCP2221A devices and associated tty device names, then try to process each device one at a time. After processing all devices, I'd like to apply reset to some of them. At this point, I'd like to understand the logic behind the devnum: how to determine the relationship between the actual physical device and the devnum? I first assumed maybe the devnum reflects the sequence of hardware detection in dmesg, however it seems not the case. After checking mcp.read_flash_info()["USB_SERIAL"], I found it is not related to USB_SERIAL either. Got stuck here.

Any suggestion is much appreciated. Thank you.

[electronicayciencia]

Hello.

After checking mcp.read_flash_info()["USB_SERIAL"], I found it is not related to USB_SERIAL either.

Have you tried using enable_cdc_serial? Never tried in Linux.

[nidorhuang]

I have tried enable_cdc_serial manually in linux, and it works well. However the MCP2221A devices does not come with CDC serial number enabled by default. Consider the case if multiple devices connected to the same host, I would like to know which device I need to init with Device(), so I can save config and reset the correct device I'm looking for (from the sysfs), not the other devices. At this point, the CDC serial is still unknown (it can only be revealed after init), so the only option left seems to be the devnum. This is where my question starts.