USART RTS is high after init

marko239955_stm1_st · ‎2014-11-18

Posted on November 18, 2014 at 14:33

I have STM32RBT6. After initialisation of USART1, the RTS remains high. The code is as follows:

/** USART1 GPIO Configuration

PA9 ------> USART1_TX

PA10 ------> USART1_RX

PA11 ------> USART1_CTS

PA12 ------> USART1_RTS

*/

GPIO_InitTypeDef GPIO_InitStruct;

USART_InitTypeDef usartinit;

NVIC_InitTypeDef NVIC_InitStructure;

/* System Clocks Configuration */

/* USART1 clock enable */

RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);

/* GPIOA clock enable */

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

/*Enable APB2 peripheral clock */

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

/* Configure USART1 RTS and USART1 Tx as alternate function push-pull */

GPIO_InitStruct.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_12;

GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF_PP;

GPIO_Init(GPIOA, &GPIO_InitStruct);

// Override RTS ToDo: check for bug in RTS handling !!!!!!!!!!!!!!!!!!!!!!!!!

GPIO_InitStruct.GPIO_Pin = GPIO_Pin_12;

GPIO_InitStruct.GPIO_Mode = GPIO_Mode_Out_PP;

GPIO_Init(GPIOA, &GPIO_InitStruct);

GPIO_ResetBits(GPIOA, GPIO_Pin_12);

/* Configure USART1 CTS and USART1 Rx as input floating */

GPIO_InitStruct.GPIO_Pin = GPIO_Pin_11 | GPIO_Pin_10;

GPIO_InitStruct.GPIO_Mode = GPIO_Mode_IN_FLOATING;

GPIO_Init(GPIOA, &GPIO_InitStruct);

/* Configure USART1, 115200 baud, harware flow control, 1 stop bit, no parity */

usartinit.USART_BaudRate = 115200;

usartinit.USART_HardwareFlowControl = USART_HardwareFlowControl_RTS_CTS;

usartinit.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;

usartinit.USART_Parity = USART_Parity_No;

usartinit.USART_StopBits = USART_StopBits_1;

usartinit.USART_WordLength = USART_WordLength_8b;

USART_Init(USART1, &usartinit);

USART_Cmd(USART1, ENABLE);

/* Enable USART1 IRQ */

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;

NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);

USART_ITConfig(USART1, USART_IT_RXNE, ENABLE); // enable IRQ on RX

NVIC_EnableIRQ(USART1_IRQn); // Enable IRQ for USART1 in NVIC

I am using STM32F10x Standard Peripherals Library 3.5.1

What am I missing?

Regards,

Marko

#stm32-usart-rts-remains-high

Tesla DeLorean · ‎2014-11-18

Posted on November 18, 2014 at 18:21

What do you have attached to the pin?

In GPIO mode you should be able to drive up/down.

In AF mode, you might want to double check the errata, seem to recall one of the CTS/RTS grouping clashing with CAN, requiring CAN to be remapped elsewhere.

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marko239955_stm1_st · ‎2014-11-18

Posted on November 19, 2014 at 00:31

Thank you. The issue is described in errata. CAN must be remapped to alternate location even when not used.

http://www.st.com/st-web-ui/static/active/en/resource/technical/document/errata_sheet/CD00190234.pdf

Workaround from section 2.8.1:

When USART1_RTS is used, the CAN must be remapped to either another IO configuration

when the CAN is used, or to the unused configuration (CAN_REMAP[1:0] set to “01�?) when

the CAN is not used.

Regards,

Marko