nRF52 TWI easyDMA feature

[FA]

Hi,

I want to know that if the TWI easyDMA in nRF52 can help in achieving this task:

• we want to read from TWI each 10msec based on a timer interrupt and write the values in an array, e.g., A

• meanwhile we want to transfer an array, e.g., B. Assume we can choose between non-connectable advertising or being in a connection.

Is this possible? Normally we should wait for the reading to finish, and then transmit in the 10msec window. Can DMA help in eliminating this sequence?

Thanks!

[endnode]

Hi,

I guess it's not EasyDMA (alone) but rather PPI (see the description here). It should be possible to launch TWI transfer upon Timer end event (all that purely in HW without need to wake or interrupt CPU) but still you will probably need some management in your app. I did similar with PWM and SPI just by using NRF drivers from SDK 10/11 (they use EasyDMA and I've used two rotating 128-byte buffers to keep the PWM continuous, you are limited to 255B for single transfer on SPI and TWI anyway). It worked with interrupts at 1ms range, so 10ms shouldn't be a problem.

Cheers Jan

[FA]

Well, I don't think the case is really complicated knowing the capability of PPI and easyDMA, which I don't have full knowledge yet. Again, the only thing needed is storing in RAM. Reading is always the same in terms of bytes, we are storing all in one array. The timer handler just does this, nothing else. At some point, we want the radio to work for let's say 100 msec. This means 10 TWI reads. We don't want to miss these reads due to radio being active.