Tool/software:
Hi,
I've been trying to use DMA for large data transfers at high speed and i came accross an issue when using DMA's interrupts.
My program is trying to send a buffer (9638 bytes) to the eUSCI A0 module configured in uart mode. The uart configuration in itself
is working as i'm able to send data through it to my PC with a serial cable.
I made two simple test functions to send the same buffer with DMA, one function uses flag polling and the other uses DMA's interrupts. Here is the code :
static void dma_send(const uint8_t *buf, size_t len){ DMACTL0 = DMA0TSEL_17; // UCA0TXIFG DMA0SA = (uint32_t)buf; DMA0DA = (uint32_t)(&UCA0TXBUF); DMA0SZ = len; DMA0CTL = ( DMADT_0 // single transfer mode | DMADSTINCR_0 // destination addess fixed | DMASRCINCR_3 // source address incremented | DMADSTBYTE | DMASRCBYTE | DMALEVEL // trigger type: level detection ); hw_toggle_led1(); DMA0CTL |= DMAEN; while (!(DMA0CTL & DMAIFG)); hw_toggle_led1();}PLACE_INTERRUPT(isr_dma)#pragma vector=DMA_VECTORstatic void __interrupt isr_dma(void){ __low_power_mode_off_on_exit(); switch (__even_in_range(DMAIV, DMAIV_DMA0IFG)) { case DMAIV_DMA0IFG: { DMA0CTL &= ~DMAIE; break; } }}static void dma_send_irq(const uint8_t *buf, size_t len){ DMACTL0 = DMA0TSEL_17; // UCA0TXIFG DMA0SA = (uint32_t)buf; DMA0DA = (uint32_t)(&UCA0TXBUF); DMA0SZ = len; DMA0CTL = ( DMADT_0 // single transfer mode | DMADSTINCR_0 // destination address fixed | DMASRCINCR_3 // source address incremented | DMADSTBYTE | DMASRCBYTE | DMALEVEL // trigger type: level detection | DMAIE // enable interrupts ); hw_toggle_led1(); DMA0CTL |= DMAEN; __low_power_mode_0(); hw_toggle_led1();}For all my tests, both MCLK and SMCLK (which is used to source the uart) are seted up with DCOCLK running at 25 MHz, using REFOCLK as reference, so the frequency is not really accurate.
I'm calling these functions and pass the buffer as parameter. With "dma_send()" i have no issue, it's working fine, i tried from baudrate 57'600 and up to 3'000'000.
With "dma_send_irq()" however, it seems to be working from baudrate 57'600 up to 1'382'400, but higher than that it's completely bugged, i'm receiving garbage characters on my computer terminal and sometimes the MSP itself crashes.
I made the tests with edge trigger detection as well but i'm getting the same result or worse.
I'd prefer to use the interrupts because the goal would be to use low power mode during the transfer, we're trying to achieve maximum data rate to transfer around 2M bytes of data as quick as possible in the real case application.
Is there an explanation for this behaviour with interrupts enabled ?
Thanks.
