TWI - Reading more that 255 packet size

[Zoran]

Hi All,

I have looked through the devzone and cannot find a solution to this. I am using the nRF52832 SDK 15.2. Working with a BNO080 IMU over TWI.

I need to read more than 255 byte packet size (276 bytes) in one pass from the sensor upon power up. The BNO080 must upload all of this data before sending IMU data.

when i try reading one byte at a time in a loop, it does not work.

Is there any way to do this?

Regards,

Zoran

[Dmitry]

Hi Zoran,

there's a hardware limitation of 52832 - one transaction is limited to 255 bytes (all other chips have much higher limitation). Here is a solution for two consecutive TX transfers without STOP/RESTART between them, I believe for RX you can do similar trick.

[Zoran]

Thanks for that. How can I enable EDMA in code after the first long sequence of data from the IMU? I thought this was just enabled in the config file?

[Dmitry]

Yes, modules are enabled in sdk_config. Try to set both NRFX_TWI_ENABLED and NRFX_TWIM_ENABLED, then create twi and twim instances with equal settings. For long sequence, call nrfx_twi_init, read your data, call nrfx_twi_uninit (release resources) then nrfx_twim_init (switch to EDMA module). I didn't do such thing and can't say whether it will work without modifications in sdk code, but it worth to try.

But first, check twi module to ensure that it works for your case )