Variable-length I2C transmissions

[mlac]

Hi there,

I must interact with an I2C slave that sends variable-length messages. The first byte of the transactions describes the length of the remaining bytes.

i2c_write_read_cb() expects a fixed number of bytes to read, so I'm unsure how to use the API to interact with this slave.

Thanks in advance!

- Laci

[Amanda Hsieh]

Hello,

Most of the staff is away for a long weekend in Norway, so there will be some delays in response time. I appreciate your patience.

[Sigurd]

Hi!

Maybe you could try splitting the operation in 2.

First a i2c_write_read_cb(), and then a i2c_read() with the rest of the bytes ?

[mlac]

Hi Sigurd,

I have to use a single I2C transaction for reading because the slave is implemented this way. Should I extend Zephyr with a special I2C read function that satisfies my requirements? Based on the API reference, I don't see any other solutions.

[Sigurd]

Hi,

Yes, that might be the best solution.  Another approach might be to use i2c_write_read_cb() with the max numbers of bytes possible to read, and then discard the excess bytes. But it sounds like creating a new special I2C read function is the best option.