Add support for Silabs (CP2102, CP210*) devices

[zpg6]

Interested in using this with CP210X devices for use with my ESP32 Dev Kit projects and other UART extenders like CP2102 MICRO USB to UART TTL.

[wuwbobo2021]

Thanks. I will probably implement it later, if you cannot do it for now.

Note for your current usage case: With ESP32-S2 and ESP32-S3, you can use dfu-nusb after gaining the device permission in android-usbser. Besides, ESP32-S2/S3/C3/C6/H2 all support USB CDC flashing in download mode, but the protocol over CDC port is probably ESP32-specific (unlike DFU).

• https://docs.rs/dfu-nusb/0.1.1/dfu_nusb/type.DfuASync.html
• https://docs.espressif.com/projects/arduino-esp32/en/latest/tutorials/cdc_dfu_flash.html
• Is USB CDC mode flashing supported in espflash? esp-rs/espflash#656 (Note that I had confused DFU with the CDC method here)

[zpg6]

@wuwbobo2021 I was thinking of RX, TX, sending breaks (TX), and detecting breaks (RX).

Didn't even have my eye on flashing the esp32 with this... cool idea.

[wuwbobo2021]

Hello. According to https://github.com/esp-rs/espflash/pull/813/files, the ESP32-specific flashing protocol over CDC port is probably available in espflash.

I was thinking of RX, TX, sending breaks (TX), and detecting breaks (RX).

Do you think the Read implementation is wrong? Should it be guaranteed that read() returns after receiving any data, but not wait for filling the slice before timing out? (side note: https://github.com/wuwbobo2021/android-bluetooth-serial-rs definitely waits for filling the slice, that's probably wrong)

PS: android-usbser may be changed to nusb-serial after merging the Android specific code into the upcoming nusb 0.2.