nRF libUART transmit data from read only memory

[liammcnair]

Hello,

I am using libUARTE and libUARTE ASYNC for reliable communication over UART. 

I need to transmit data that is stored in read only memory but this module seems to only support transmitting data from read/writable memory. Is there any way to do this other then to make a copy of all the data to another location?

I am using existing code that I should not be changing and it stores a bunch of predefined data packets in read only memory. I could probably change the linker script to store my constant data in read/write memory but that is not a great solution either.

It seems very odd that this module doesn't support transmitting data from constant data (I've never experienced an SDK like this). I'm sure someone had a reason for implementing it this way, I am curious as to why?

If I pass the data from read only memory then nothing gets written out the UART.

Any advice is much appreciated!

Thanks,

Liam

I am using:

SDK: nRF SDK 17.0.2

Device: nRF52840

Compiler: armgcc

[Vidar Berg]

Hello Liam,

This is a HW limitation, unfortunately. The EasyDMA can only access data from RAM, not flash. 

Best regards,

Vidar

[liammcnair]

Thanks Vidar, that makes sense. I hadn't thought of the possibility that it is a hardware limitation. I guess we will either copy data to RAM or not use DMA. I think the best solution in the long rung run will be to store the data in ram.

Thanks again,

Liam