EDMA with UART5 on Tower K64

razed11 — Sat, 15 Dec 2018 00:39:36 GMT

I am using the Tower system with a K64 and serial board. Starting with the EDMA UART example that comes with SDK 2.4.2 I modified the defines to use UART5 (the UART that connects to the serial board RS-232 level shifter). I simplified the body of the example in the following way:

UART_ReceiveEDMA(DEMO_UART, &g_uartEdmaHandle, &receiveXfer);

U32 count = ~0;

while (1)
{
U32 subcount;

UART_TransferGetReceiveCountEDMA(DEMO_UART, &g_uartEdmaHandle, &subcount);

if (subcount != count)
{
count = subcount;

printf("Count: %d\n", count);

}

sleep(10);
}

When I connect to a terminal emulator I can see the message sent using UART_SendEDMA (not shown).

If I press a key once I can see that the receive DMA buffer is immediately filled with that single character and the callback occurs. The count reported by the task remains at zero.

Is there a problem with using UART5? I noticed that there are not separate enumerations for RX and TX in the DMA MUX definition as there are for some UARTs but only kDmaRequestMux0UART5.

#define DEMO_UART UART5

#define DEMO_UART_CLKSRC kCLOCK_BusClk

#define DEMO_UART_CLK_FREQ 60'000'000

#define UART_TX_DMA_CHANNEL 0U

#define UART_RX_DMA_CHANNEL 1U

#define EXAMPLE_UART_DMAMUX_BASEADDR DMAMUX0

#define EXAMPLE_UART_DMA_BASEADDR DMA0

#define UART_TX_DMA_REQUEST kDmaRequestMux0UART5

#define UART_RX_DMA_REQUEST kDmaRequestMux0UART5

#define ECHO_BUFFER_LENGTH 8

Reading elsewhere it seems that there is no way to pull data from the receive buffer until the exact number is specified. I found this surprising as very often the number of bytes is unknown. For example, I am reading from a bar code scanner and the code ends with a carriage return. So I need the ability to pull data out of the buffer until I see that character.

Re: EDMA with UART5 on Tower K64

mjbcswitzerland — Sat, 15 Dec 2018 04:18:10 GMT

Kenny

The K64 UARTs 4 and 5 have a single DMA channel and so one can use either Rx DMA or Tx DMA on each but not both at the same time.

Regards

Mark

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EDMA with UART5 on Tower K64

Re: EDMA with UART5 on Tower K64