TWI maximum data transfer size in nRF52832

[Mariusz_ELP]

Is it possible to transfer 258 bytes over the TWI interface of the nRF52832 in one transaction ? The manual says that RXD.MAXCNT is 8 bit wide only. I need to read 258 bytes in one transaction. Is it possible on this device ? Thank you for help.

[Susheel Nuguru]

The maximum you can read is only 255 bytes in one transaction. This is, unfortunately, a hard limitation. But you can try to use EasyDMA List, split it into two 129 bytes transaction. You would get all 258 bytes this way by triggering just one TWI call, but there would be a stop/start bit after 129 bytes has been transferred. If your device can live with it, then listing is a way to go. Some solutions do not want the stop/start bit injected (that is they need it to be one single transaction without any stop/start bits injected), in this case the maximum single transaction is 255 bytes long.

[Mariusz_ELP]

Thank you for the confirmation. Unfortunately the stop/start bit is not allowed in my data transfer. I have to do it in one transaction. Fortunately the limitation is not critical in my project. I can skip and mask these last 3 bytes of data. Is there any other nRF device, which support longer transfers ? Thank you!

[awneil]

Mariusz_ELP said:

Is there any other nRF device, which support longer transfers ?

I think nRF52840 and nRF52810 ?

[Susheel Nuguru]

Yes , instead of nRF52832, you can use below

nRF52810 - 10 bit MAXCNT 

nRF52811 -  14 bit MAXCNT

nRF52840 -  16-bit MAXCNT

Choose the best one that suits best in your memory/peripheral needs 

[Mariusz_ELP]

Thanks !