TWI master driver stops sending after successful transfer of 2 bytes

RE: TWI master driver stops sending after successful transfer of 2 bytes

Vidar Berg — Fri, 05 Mar 2021 14:33:24 GMT

Thanks for the update Marko, glad to hear that you found a way to get around this. To me it looks like the problem could be that the slave doesn't release the clock line for some reason and thus preventing the master from clocking out the last byte.

I think it could be interesting to try compare the scope traces of when it works and when it doesn't.

RE: TWI master driver stops sending after successful transfer of 2 bytes

mhammer3 — Fri, 05 Mar 2021 14:26:07 GMT

Hi Vidar

thanks for you reply.

1. Yes, the I2C SCK line remains low after the byte of 36. It should still send the byte of 0x82.

2. No, I have not. It always stops after address + 1 byte of data.

3. 0x36 0x82 is the command of getting the serial identifier. it is not documented in the data sheet, but is used in the sample code provided by Sensirion: https://github.com/Sensirion/embedded-sgp. I verified on a STM32L462RE device this command is working fine.

Anyway, in the meantime I switched to using the Zephyr device driver model analog to the example of "v1.5.0\zephyr\samples\boards\bbc_microbit\line_follower_robot".

This working fine for me.

Although I am curious as to why using the twi driver directly does not work for me, I am good for now and we can close this ticket. I will let you know in case I need to use the driver directly again.

Thanks again for your help.

Marko

RE: TWI master driver stops sending after successful transfer of 2 bytes

Vidar Berg — Fri, 05 Mar 2021 13:43:17 GMT

Hi Marko,

I haven't really studied the data sheet for this particular sensor yet, but I have a few quick follow up questions I was hoping you could answer first:

1. Does the clock signal low remain low after you have sent the last 0x36 byte?

2. Have you able to send multiple bytes for other commands?

3. What is 0x36 0x82 supposed to do. I didn't find 0x82 mentioned anywhere in the datasheet.

Best regards,

Vidar

RE: TWI master driver stops sending after successful transfer of 2 bytes

mhammer3 — Thu, 04 Mar 2021 13:33:53 GMT

All, please note the heading of this ticket is incorrect.

A better title is:

TWI master driver stops sending after successful transfer of slave address + 1 data byte