Document maximum I2C transfer size of 64 bytes
maxgerhardt opened this issue · 5 comments
Nowhere in the code is it mentioned that I2C write calls of up to only 64 bytes are allowed -- all bigger transfers will fail with error message
onion-i2c:: write issue for register 0x01, errno is 122: Not supported
Debug output from your liboniondebug when such a write is requested:
onion-i2c:: writing buffer:
buffer[0]: 0x01
buffer[1]: 0xab
buffer[2]: 0xab
buffer[3]: 0xab
buffer[4]: 0xab
buffer[5]: 0xab
buffer[6]: 0xab
buffer[7]: 0xab
buffer[8]: 0xab
buffer[9]: 0xab
buffer[10]: 0xab
buffer[11]: 0xab
buffer[12]: 0xab
buffer[13]: 0xab
buffer[14]: 0xab
buffer[15]: 0xab
buffer[16]: 0xab
buffer[17]: 0xab
buffer[18]: 0xab
buffer[19]: 0xab
buffer[20]: 0xab
buffer[21]: 0xab
buffer[22]: 0xab
buffer[23]: 0xab
buffer[24]: 0xab
buffer[25]: 0xab
buffer[26]: 0xab
buffer[27]: 0xab
buffer[28]: 0xab
buffer[29]: 0xab
buffer[30]: 0xab
buffer[31]: 0xab
buffer[32]: 0xab
buffer[33]: 0xab
buffer[34]: 0xab
buffer[35]: 0xab
buffer[36]: 0xab
buffer[37]: 0xab
buffer[38]: 0xab
buffer[39]: 0xab
buffer[40]: 0xab
buffer[41]: 0xab
buffer[42]: 0xab
buffer[43]: 0xab
buffer[44]: 0xab
buffer[45]: 0xab
buffer[46]: 0xab
buffer[47]: 0xab
buffer[48]: 0xab
buffer[49]: 0xab
buffer[50]: 0xab
buffer[51]: 0xab
buffer[52]: 0xab
buffer[53]: 0xab
buffer[54]: 0xab
buffer[55]: 0xab
buffer[56]: 0xab
buffer[57]: 0xab
buffer[58]: 0xab
buffer[59]: 0xab
buffer[60]: 0xab
buffer[61]: 0xab
buffer[62]: 0xab
buffer[63]: 0xab
buffer[64]: 0xab
onion-i2c:: write issue for register 0x01, errno is 122: Not supported
The used function was i2c_writeBufferRaw.
Could this transfer size also be increased? Some chips (e.g. I2C to SPI bridges) will allow for higher transfer sizes (in that case, 200 bytes). With the 64 byte limit that would take 4 I2C write calls instead of one if the limit was higher.
As far as I recall, the limit is 256 bytes in hardware. Can't remember where I saw that tho.
I'll set it to 256 and we can try it out
@maxgerhardt Release v0.7 of libonioni2c that includes this change. Please try it out and let me know how it goes
This issue still prevails with the newest version. It results in the same error message when trying to write 65 bytes or more: onion-i2c:: write issue for register 0x01, errno is 122: Not supported (thrown in https://github.com/OnionIoT/i2c-exp-driver/blob/master/src/lib/onion-i2c.c#L108). I think this needs changes deeper in the kernel code? The driver just write()s to the device file and the I2C device file rejects it.
Update: I did update to the newest 0b188 version by doing a factory reset & oupgrade, result is still the same.
Per https://onion.io/2bt-i2c-firmware-update/ this should be fixed, but I don't see any new commit here or in the LEDE source repository. Where are the changes for validation?
You are correct, firmware b194 and up should have this fixed. See this commit in the Onion LEDE source repo: OnionIoT/source@0ea89f4