UART to send command like generic terminal

Stephen Keng

Intellectual 560 points

Hi all,

I've been trying to operate a motor controller via RS232 from TIVA.

SCX11 controller RS-232c Specification:

Transmission - Start-stop synchronous method, NRZ (Non-Return Zero), full-duplex

Data length - 8bits, 1stop, no parity

Transmission speed - 9600

Protocol - TTY (CR+LF)

Terminal Specification
• ASCII mode
• VT100 compatible recommended
• Handshake: None
• Transmission CR: C-R
• Word wrap: None
• Local echo: None
• Beep sound: ON

My code:

void	CUART::initRS(void)
{
    //
    // Enable the GPIO Peripheral used by the UART.
    //
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOP);

    //
    // Enable UART6
    //
    SysCtlPeripheralEnable(SYSCTL_PERIPH_UART6);


    UARTConfigSetExpClk(UART6_BASE, _ui32SysClock, 9600,  	//was 8*115200
                            (UART_CONFIG_WLEN_8 | UART_CONFIG_STOP_ONE |
                             UART_CONFIG_PAR_NONE));
    UARTDisable(UART6_BASE);

    //
    // Configure GPIO Pins for UART mode.
    //
    GPIOPinConfigure(GPIO_PP0_U6RX);
    GPIOPinConfigure(GPIO_PP1_U6TX);
    GPIOPinTypeUART(GPIO_PORTP_BASE, GPIO_PIN_0 | GPIO_PIN_1);

    UARTEnable(UART6_BASE);
    //
    // Initialize the UART for console I/O.
    //
//    UARTStdioConfig(7, 9600, _ui32SysClock);

}

/*___________________________________________________
 *
 *
 */
void	CUART::txRS(char ascii)
{
	UARTCharPut(UART6_BASE, ascii);

}

/*___________________________________________________
 *
 *
 */

void	CUART::txSCX()
{
	char command;

	command = 'm';
	txRS(command);
	command = 'a';
	txRS(command);
	command = ' ';
	txRS(command);
	command = '1';
	txRS(command);

command = 0x0d;
txRS(command);
command = 0x0a;
txRS(command);

I looked into the terminal and see that the TIVA is only sending “m/r /n” instead of “ma 1/r/n”

See attached picture. First line is PC attempt, second line is TIVA attempt.

Looking through the forum posts I realized I may need delay/interrupt but I'm unsure if that is the cause of the problem

Any help appreciated

Thanks,

Stephen

over 10 years ago

0 Stephen Keng over 10 years ago

Intellectual 560 points

The controller works when there is delay between bytes.

void	CUART::txSCX()
{
	char command;
	uint32_t num = 120000;

	command = 'm';
	txRS(command);
	SysCtlDelay(num);
	command = 'a';
	txRS(command);
	SysCtlDelay(num);
	command = ' ';
	txRS(command);
	SysCtlDelay(num);
	command = '1';
	txRS(command);
	SysCtlDelay(num);
	command = 0x0d;
	txRS(command);
	SysCtlDelay(num);
	command = 0x0a;
	txRS(command);
}

A delay of 3ms is required between bytes sent.

Is there a more elegant method?

0 Amit Ashara over 10 years ago

TI__Guru**** 244400 points

Hello Stephen

Instead of using UARTCharPut if you replace it with the following then does it still work w/o adding the 3 ms delay.

SysCtlDelay(100);
while(HWREG(UART6_BASE + UART_O_FR) & UART_FR_TXFF)
{
}
HWREG(UART6_BASE+ UART_O_DR) = ascii;

Also it would be worth checking in the original code

1. Is the character showing on U0TX
2. Is the TXFIFO Enabled before the transmission (UARTEnable should do that)

Regards
Amit

0 Stephen Keng over 10 years ago in reply to Amit Ashara

Intellectual 560 points

Hi Amit,

The replacement you suggested does not work.
I assume it is because the while loop "delay" is not long enough...

Cheers,
Stephen

0 Amit Ashara over 10 years ago in reply to Stephen Keng

TI__Guru**** 244400 points

Hello Stephen,

What about the #1 and #2?

Regards
Amit

0 Stephen Keng over 10 years ago in reply to Amit Ashara

Intellectual 560 points

Sorry, did you mean U6TX? I might be misinterpreting things
#1 Because U0TX is being used for another purpose. U6TX sends "m" like before
#2 UARTEnable(UART6_BASE); is called before CUART::txSCX()

0 Amit Ashara over 10 years ago in reply to Stephen Keng

TI__Guru**** 244400 points

Hello Stephen,

Yes, I meant U6TX. Do all the characters being sent w/o delay show up on the U6TX or does only "m" come up?

Regards
Amit

0 Stephen Keng over 10 years ago in reply to Amit Ashara

Intellectual 560 points

I only see "m" on terminal when I use your code (no delays between bytes)

When I use a delay I see "ma 1"

Maybe 3ms delay is necessary?

0 Amit Ashara over 10 years ago in reply to Stephen Keng

TI__Guru**** 244400 points

Hello Stephen,

It seems that the issue is on the PC side application that it cannot accept characters that fast. May be flow control would be required to get rid of the Delay Loop.

Regards
Amit

0 Stephen Keng over 10 years ago in reply to Amit Ashara

Intellectual 560 points

Hi Amit,

I figured that as well. Thanks for helping

Stephen

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UART to send command like generic terminal