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EK-TM4C123GXL: usb_dev_serial example to other uart port

Fabian Schmitter
Prodigy 10 points
Part Number: EK-TM4C123GXL

I do not make it to redirect the usb-serial to another uart than uart0.

In usb_dev_serial i changed the uart defines to match uart1:

#define USB_UART_BASE        UART1_BASE
#define USB_UART_PERIPH   SYSCTL_PERIPH_UART1
#define USB_UART_INT            INT_UART1
#define TX_GPIO_BASE            GPIO_PORTB_BASE
#define TX_GPIO_PERIPH       SYSCTL_PERIPH_GPIOB
#define TX_GPIO_PIN               GPIO_PIN_1
#define RX_GPIO_BASE           GPIO_PORTB_BASE
#define RX_GPIO_PERIPH       SYSCTL_PERIPH_GPIOB
#define RX_GPIO_PIN               GPIO_PIN_0

In  startup_ccs.c i changed:

void (* const g_pfnVectors[])(void) = {
....
IntDefaultHandler         // UART0 Rx and Tx
USBUARTIntHandler,   // UART1 Rx and Tx
...}

What am i missing?

  • 0
    TI__Guru*** 135225 points

    Hello Fabian,

    Can you explain what issue you are running into? I presume you have FTDI cable attached to UART1 that is then connected to the PC? If so, what behavior are you seeing when you try and send messages?

    Best Regards,

    Ralph Jacobi

  • 0 in reply to Ralph Jacobi
    Prodigy 10 points

    Hello Ralph,

    When i write to the USB Virtual COM-Port the Green On-Board Led flahes with every transmitted byte (as in the example), this seems to work. But it doesnt foward the the Byte to UART1.
    In the other direction the blue Led should flash with every transmitted Byte on UART1, but it doesn't transmit/receive anything over UART1. In the code the USBUARTIntHandler is never reached.

    Yes, my first try was an attached FTDI TTL-232R-RPi Cable. After not getting an uart response from the TIVA i checked with an oscilloscope whether the UART GPIOs toggle. With the FTDI Cable attached, the FTDI Chip transmitts data with the same baud (9600) as set in the TIVA-Code. With only a probe attached to Pins PB0 & PB1 both GPIOs keep beeing low .

    Accordingly, I suspect that UART1, its Interrupt or its GPIOSs are not properly initialised.

    Best regards,
    Fabian

  • 0 in reply to Fabian Schmitter
    TI__Guru*** 135225 points

    Hello Fabian,

    Did you change the DEFAULT_BIT_RATE to 9600? The example is set to run at 115200.

    I can try and test this out with my own FTDI cable tomorrow and see what I can observe, but any detailed investigation may need to wait until Friday.

    Best Regards,

    Ralph Jacobi

  • 0 in reply to Ralph Jacobi
    Prodigy 10 points

    Hello Ralph,

    Yes I also tried different baud rates (9600 & 115200), of course i matched to baudrate on the tiva-board with the settings on my computer (I use putty as terminal). Beside UART1 i also tried UART3 & UART5. No change in behaviour was observed.

    Best regards,
    Fabian

  • 0 in reply to Fabian Schmitter
    TI__Guru*** 135225 points

    Hello Fabian,

    I've been trying to find a solution to the issue with this but haven't been able to work out something yet.

    From what I can tell the issue is that the USB library thinks the UART port is tied up, and the reason may be that there are a couple error bits set for some reason.

    When testing with the ICDI, I don't see these bits getting set and the interface works fine. But something with the FTDI cable is causing the UART peripheral to trip those errors. Even after adding multiple clears and a check in the ISR for the error interrupt I was not able to get it working yet.

    Unfortunately I can't spend further time investigating this today. I will see if I can get back to it on Monday or otherwise pass it on to a colleague to try and debug further. 

    Best Regards,

    Ralph Jacobi

  • +1 in reply to Fabian Schmitter
    TI__Guru**** 184436 points

    Hi,

      I think the problem is that the code is missing the pinmuxing code. I tried on UART1 with PB0 (for RX) and PB1 (for TX) and it is working for me. You need to add the below two lines. 

    MAP_SysCtlPeripheralEnable(TX_GPIO_PERIPH);
    MAP_SysCtlPeripheralEnable(RX_GPIO_PERIPH);
    GPIOPinConfigure(GPIO_PB0_U1RX);
    GPIOPinConfigure(GPIO_PB1_U1TX);
    MAP_GPIOPinTypeUART(TX_GPIO_BASE, TX_GPIO_PIN);
    MAP_GPIOPinTypeUART(RX_GPIO_BASE, RX_GPIO_PIN);

  • 0 in reply to Charles Tsai
    Prodigy 10 points

    Hi Charles

    Thank you very much, this resolved my issue. UART3 and different Baudrates are also working with those both Pins initalised.
    I added the folling lines of code for UART3:

    Added on top of File with the other defines:
    #define TX_UART_PIN            GPIO_PC7_U3TX
    #define RX_UART_PIN            GPIO_PC6_U3RX

    Added to main function:
    ROM_GPIOPinConfigure(TX_UART_PIN);
    ROM_GPIOPinConfigure(RX_UART_PIN);

    Best regards,
    Fabian