i2c_burst_write difference nrf52 and nrf91 series

RE: i2c_burst_write difference nrf52 and nrf91 series

Simon — Wed, 03 Feb 2021 12:40:33 GMT

I looked into this, and got a better overview of what's going on.

When writing to a register, the following should appear on the SDA line:

Send start command
Send 7 bit start address + write bit
Send register address
Send data to be written to the register

You are trying to write 0xC688 to the configuration register with address 0x01 of an I2C slave with address 0x88.

What the nRF52840 does, based on the trace

Send start command
Send 7 bit start address (0x88) + write bit
Send register address (0x01)
Send data to be written to the register (0xC6 + 0x08)

What the nRF9160 does, based on the trace

Send start command
Send 7 bit start address (0x88) + write bit
Send register address (0x01)
Send 7 bit start address (0x88) + write bit
- This is where it differs from the nrf52, it splits the message up in two pieces
Send register address (0xC6)
Send data to be written to the register (0xC6 + 0x08)
- This is why it fails, because this is not register 0x01
Send data (0x08)

I suspect the issue is that for the nRF9160, the function i2c_nrfx_twim_transfer() does not concatenate the messages for some reason, and calls nrfx_twim_xfer() two times. I'm not sure why if this is the case.

Could you try to do some debugging in the function i2c_nrfx_twim_transfer(), both when the nRF52840 is used, as well as the nRF9160. Check if nrfx_twim_xfer() is called one or two times.

By the way if "nordic,nrf-twim" is set in the dts/overlay file, i2c_nrfx_twim.c will be used, and if "nordic,nrf-twi" is set, i2c_nrfx_twi.c will be used

Best regards,

Simon

RE: i2c_burst_write difference nrf52 and nrf91 series

Maaike — Fri, 22 Jan 2021 07:53:53 GMT

As expected using i2c_write instead of i2c_burst_write solved my problem.
I do still wonder why i2c_burst_write does not work on the nRF91 and it does work on the nRF52.

Kind regards,
Maaike

RE: i2c_burst_write difference nrf52 and nrf91 series

Simon — Mon, 18 Jan 2021 08:38:43 GMT

Have you gotten any progress on this? Pull request 25867 may be helpful, it adds an option to concat smaller payloads.

Best regards,

Simon

RE: i2c_burst_write difference nrf52 and nrf91 series

Simon — Wed, 06 Jan 2021 13:14:27 GMT

Sorry for the delay on this. I'm back at work and will look into this case.

Best regards,

Simon

RE: i2c_burst_write difference nrf52 and nrf91 series

Maaike — Tue, 29 Dec 2020 09:23:12 GMT

I was able to check it with the logic analyser and there is a difference between the nrf52 and nrf91 in writing to the configuration register. In the reading of the ID register there is no difference.

Some addresses and values:
I2C address read = 0x44
I2C address write = 0xC4
MANUFACTURER_ID register address = 0x7E
CONFIGURATION register address = 0x01
MANUFACTURER_ID = 0x5449
Configuration value to write = 0b1100011xxxx01000, where x are read only fields.
Expected configuration value to read = 0xC688 (0b1100011010001000)

Below the read ID register and the write and read to the configuration register of both the nrf91 and nrf52 are posted.

nrf91 read ID register

nrf52 read ID register

nrf91 write read configuration register

nrf52 write read configuration register

RE: i2c_burst_write difference nrf52 and nrf91 series

Simon — Thu, 24 Dec 2020 00:30:41 GMT

A huge part of the support team are currently on Christmas vacaction, and you may experience delayed answers. Most of the staff will be back by january 4th and you can expect an answer after then. My apologies for this.

Best regards,

Simon

RE: i2c_burst_write difference nrf52 and nrf91 series

Maaike — Wed, 23 Dec 2020 13:36:50 GMT

Hi Simon,

I will check the i2c output with the logic analyser.
Due to the Christmas holidays it might take a week (or 2) till I can get back to you with the results.

Have a good holiday!
Kind regards,
Maaike

RE: i2c_burst_write difference nrf52 and nrf91 series

Simon — Wed, 23 Dec 2020 12:52:28 GMT

Could you try to attach a logic analyzer to the I2C pins and see if the output differs between the nRF52 and the nRF91 when you use the i2c_burst_write function. That would be interesting to see. I'll soon take christmas vacation for some days, so I don't have time to do it myself before then.

Best regards,

Simon