USART Hardware Handshaking

mvi · ‎2008-05-02

Posted on May 02, 2008 at 18:37

mvi · ‎2011-05-17

Posted on May 17, 2011 at 12:34

Hello!

Can someone tell me whether I should take care of any special events on the ISR when the Hardware Handshaking (RTS/CTS) is enabled on a USART?

Or is this automatically done by the hardware, and the data sending or receiving automatically stalled so that an interrupt is not set off?

Code:

if(USART_GetITStatus(USART3, USART_IT_RXNE) != RESET) {

USART_ClearITPendingBit(USART3, USART_IT_RXNE);

}

if(USART_GetITStatus(USART3, USART_IT_TXE) != RESET) {

USART_ClearITPendingBit(USART3, USART_IT_TXE);

}

-Mad D

mvi · ‎2011-05-17

Posted on May 17, 2011 at 12:34

Hi again!

I checked the USART example1, looks like its automatically taken care of... Am I correct?

mvi · ‎2011-05-17

Posted on May 17, 2011 at 12:34

Hello yet again!

As I have mentioned. Im trying to get the USART working with the CTS/RTS signals for flow control.

I have managed to get the receiption working with no extra coding needed than when using it without the CTS/RTS signals. But the TX doesnt seem to be working right.

1) I have verified that the ISR for TX is called.

2) I checked the RX and TX pins, and RX is high where as TX is low.

3) The RTS/CTS pins are both low.

Code:

void USART_Config_Default(void) { // USART3 default configuration /* USART3 configured as follow: - BaudRate = 115200 baud - Word Length = 8 Bits - One Stop Bit - No parity - Hardware flow control enabled (RTS and CTS signals) - Receive and transmit enabled - USART Clock disabled - USART CPOL: Clock is active low - USART CPHA: Data is captured on the second edge - USART LastBit: The clock pulse of the last data bit is not output to the SCLK pin */ USART_InitStructure.USART_BaudRate = 115200; USART_InitStructure.USART_WordLength = USART_WordLength_8b; USART_InitStructure.USART_StopBits = USART_StopBits_1; USART_InitStructure.USART_Parity = USART_Parity_No; USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_RTS_CTS; USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx; USART_InitStructure.USART_Clock = USART_Clock_Disable; USART_InitStructure.USART_CPOL = USART_CPOL_Low; USART_InitStructure.USART_CPHA = USART_CPHA_2Edge; USART_InitStructure.USART_LastBit = USART_LastBit_Disable; /* Configure the USART3 */ USART_Init(USART3, &USART_InitStructure); /* Enable the USART Receive interrupt: this interrupt is generated when the USART3 receive data register is not empty */ USART_ITConfig(USART3, USART_IT_RXNE, ENABLE); /* Enable USART3 */ USART_Cmd(USART3, ENABLE); } void USART3_IRQHandler(void) { // Transmit Data Register Empty. New data can be copied for transmission. if(USART_GetITStatus(USART3, USART_IT_TXE) != RESET) { if (!GPIO_ReadOutputDataBit(GPIOA, GPIO_Pin_7)) { GPIO_SetBits(GPIOA, GPIO_Pin_7); } else { GPIO_ResetBits(GPIOA, GPIO_Pin_7); } if (bTXReadCount < bTXWriteCount) { if (!GPIO_ReadInputDataBit(GPIOB, GPIO_Pin_13)) { // Write one byte to the transmit data register. USART_SendData(USART3, bTXBuffer[bTXReadCount++]); } } else { // Disable the USART3 Transmit interrupt. USART_ITConfig(USART3, USART_IT_TXE, DISABLE); // Reset the indexes. bTXReadCount = 0; bTXWriteCount = 0; // Enable USB endpoint for receiption. SetEPRxValid(ENDP3); } // Clear the USART3 transmit interrupt. USART_ClearITPendingBit(USART3, USART_IT_TXE); } }

Any suggestions?

-Mad D

[ This message was edited by: mvi on 02-05-2008 21:52 ]

[ This message was edited by: mvi on 02-05-2008 21:58 ]

mvi · ‎2011-05-17

Posted on May 17, 2011 at 12:34

Fixed it!

The Rx and Tx init was flipped!!! So Tx was a input acting like pin at high impedance! 🙂