LeafLabs Garden » Topic: Serial DMA

LeafLabs Garden » Topic: Serial DMA http://forums.leaflabs.com/topic.php?id=9752 A place to share, learn, and grow... en-US Fri, 22 Jan 2016 00:26:11 +0000 http://bbpress.org/?v=1.0.2 <![CDATA[Search]]> q http://forums.leaflabs.com/search.php jpopadic on "Serial DMA" http://forums.leaflabs.com/topic.php?id=9752#post-21429 Mon, 03 Dec 2012 11:56:07 +0000 jpopadic 21429@http://forums.leaflabs.com/ In my case, it's channel 3 (I'm interested in Rx on USART3), so I was OK from the start (the IRQ was coming through fine, just borked data). USART_DMA_DEV and USART_RX_DMA_CHANNEL are defined at the top of my file to be DMA1 and DMA_CH3, respectively, so no real change there. Swapping DMA_SIZE_8BITS for DMA_SIZE_32BITS on the source side did the trick. gbulmer on "Serial DMA" http://forums.leaflabs.com/topic.php?id=9752#post-21427 Mon, 03 Dec 2012 10:42:04 +0000 gbulmer 21427@http://forums.leaflabs.com/ jpopadic - Rapid detective work, and thank you for posting a solution. However, my reading of that thread, and especially this, the final post: <a href="http://forums.leaflabs.com/topic.php?id=1719#post-10670" rel="nofollow">http://forums.leaflabs.com/topic.php?id=1719#post-10670</a> is that the transfer can be 8bits, but the important parameter was the DMA channel, which needed to be "DMA1, DMA_CH4" I notice that the DMA channel in your posted code has changed from "DMA1, DMA_CH3", which, if I've understood that other thread would not work, to "USART_DMA_DEV, USART_RX_DMA_CHANNEL". What are the values for these? jpopadic on "Serial DMA" http://forums.leaflabs.com/topic.php?id=9752#post-21425 Mon, 03 Dec 2012 09:25:58 +0000 jpopadic 21425@http://forums.leaflabs.com/ Solved my problem myself. Here's the solution for anyone who cares :-) It looks like the USART needs to be accessed as 16- or 32- bits (<a href="http://forums.leaflabs.com/topic.php?id=1719#post-10654" rel="nofollow">http://forums.leaflabs.com/topic.php?id=1719#post-10654</a>) Changing the DMA setup to the following makes everything work: <pre><code>dma_setup_transfer( USART_DMA_DEV, USART_RX_DMA_CHANNEL, &USART_DEV->regs->DR, DMA_SIZE_32BITS, rx_buf, DMA_SIZE_8BITS, (DMA_MINC_MODE | DMA_CIRC_MODE | DMA_TRNS_CMPLT));</code></pre> jpopadic on "Serial DMA" http://forums.leaflabs.com/topic.php?id=9752#post-21422 Mon, 03 Dec 2012 07:37:29 +0000 jpopadic 21422@http://forums.leaflabs.com/ Replying to myself... It looks like the current revision of the example (<a href="https://github.com/leaflabs/libmaple/blob/master/examples/test-usart-dma.cpp" rel="nofollow">https://github.com/leaflabs/libmaple/blob/master/examples/test-usart-dma.cpp</a>) has been updated to use a new API, that isn't in the latest IDE installer. A peek at an earlier revision (<a href="https://github.com/leaflabs/libmaple/blob/b8f61070b0be0dcd539b6563c5820719d841412f/examples/test-usart-dma.cpp" rel="nofollow">https://github.com/leaflabs/libmaple/blob/b8f61070b0be0dcd539b6563c5820719d841412f/examples/test-usart-dma.cpp</a>) is a lot more illuminating. jpopadic on "Serial DMA" http://forums.leaflabs.com/topic.php?id=9752#post-21419 Mon, 03 Dec 2012 06:26:29 +0000 jpopadic 21419@http://forums.leaflabs.com/ I'm trying to use DMA with USART3 to grab some incoming serial data and am having some problems. The interrupt is firing too quickly (chars sent way below TRANSFER_SIZE) and the data isn't written to the right spot (seeing a stack of zeros). The libmaple example here (<a href="https://github.com/leaflabs/libmaple/blob/master/examples/test-usart-dma.cpp" rel="nofollow">https://github.com/leaflabs/libmaple/blob/master/examples/test-usart-dma.cpp</a>) is woefully out of date. Does anyone have a better example? My (truncated) code (v0.0.12): <pre><code>#include <dma.h> #define TRANSFER_SIZE 16 char bytesReceived[TRANSFER_SIZE]; volatile bool dataReady = false; void DMAEvent(){ dma_irq_cause event = dma_get_irq_cause(DMA1, DMA_CH3); switch(event) { case DMA_TRANSFER_COMPLETE: dma_disable(DMA1, DMA_CH3); SerialUSB.println("done."); dataReady = true; break; } } void setup() { dataReady = false; Serial3.begin(9600); USART3->regs->CR3 = USART_CR3_DMAR; // set DMA request on Rx bit dma_init(DMA1); dma_setup_transfer( DMA1, DMA_CH3, &USART3->regs->DR, DMA_SIZE_8BITS, bytesReceived, DMA_SIZE_8BITS, (DMA_MINC_MODE | DMA_CIRC_MODE | DMA_FROM_MEM | DMA_TRNS_CMPLT)); dma_attach_interrupt(DMA1, DMA_CH3, DMAEvent); dma_set_priority(DMA1, DMA_CH3, DMA_PRIORITY_VERY_HIGH); dma_set_num_transfers(DMA1, DMA_CH3, TRANSFER_SIZE); dma_enable(DMA1, DMA_CH3); } void loop() { if(dataReady) { SerialUSB.println("read it back..."); dataReady = false; for(int i = 0; i < TRANSFER_SIZE; ++i) { SerialUSB.print(bytesReceived[i]); } } }</code></pre> Thanks! John