topic Re: Update DMA source buffer before software trigger in MCUXpresso SDK

Update DMA source buffer before software trigger

r_poelstra — Thu, 11 Feb 2021 10:18:22 GMT

Hi,

I've configured a USART TX DMA channel (using the graphical config tool) that I trigger from software when bytes are available to be transmitted using:

DMA_DoChannelSoftwareTrigger(DMA0_DMA_BASEADDR, DMA0_LOG_UART_DMA_CHANNEL);

This works fine, but only with a fixed number of bytes each trigger.

How can I update the DMA channel so it knows how many bytes it should transfer?

Thanks in advance.

Kind regards,

Remco Poelstra

Re: Update DMA source buffer before software trigger

ZhangJennie — Thu, 18 Feb 2021 09:11:29 GMT

Please let us know your chip part number, thus we can assign right engineer for your issue.

Thanks,

Jun Zhang

Re: Update DMA source buffer before software trigger

r_poelstra — Thu, 18 Feb 2021 09:13:56 GMT

Hi,

I'm using LPC844.

Kind regards,

Remco Poelstra

Re: Update DMA source buffer before software trigger

Alice_Yang — Fri, 19 Feb 2021 09:59:17 GMT

Hello Remco Poelstra,

Yes, the DMA only can transfer fixed number of bits.

And a ring buffer DMA maybe suit for you , there is demo"lpcxpresso845max_usart_transfer_rb_dma" under SDK, you can have a look.

Regards,

Alice

Re: Update DMA source buffer before software trigger

r_poelstra — Tue, 23 Feb 2021 10:27:06 GMT

Thanks for the reply.

I'll look into the ring buffer example. It might indeed be what I need.

Kind regards,

Remco Poelstra