F4Discovery using UART1

[chrispadbury]

Posted on March 26, 2012 at 16:03

Hi, I not having much success with using the UART (USART1) on my F4Discovery board (STM32F407). I am pretty new to STM32 and Keil (the IDE I am using). Here's my code:

&sharpinclude ''stm32f4_discovery.h''

&sharpinclude ''stm32f4xx_usart.h''

&sharpinclude ''stm32f4xx.h''

void usartSetup(void);

void USART_PutChar(uint8_t ch);

int main (void) {

    usartSetup();

    USART_PutChar(0);   //I realise this won't send a 0

    USART_PutChar(8);   //I realise this won't send an 8

    USART_PutChar(255);   //I realise this won't send a 255

    while (1) {

        //loop forever

    }

}

void usartSetup (void) {

    USART_InitTypeDef USART_InitStructure;

    //USART_StructInit(&USART_InitStructure);

    USART_InitStructure.USART_BaudRate = 9600;

    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_None;

    USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;

    USART_Init(USART1, &USART_InitStructure);

    USART_Cmd(USART1, ENABLE);

}

void USART_PutChar(uint8_t ch) {

    USART_SendData(USART1, (uint16_t) 0x49);

    while(USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET);

    USART_SendData(USART1, (uint16_t) 0x49);

}

 I'd be very grateful if someone could help. It never sends the 0x49 out of the UART1 TX (have checked pin PA9 and PB6) and then gets endlessly stuck on the while(USART_GetFlagStatus...). I am observing using the Keil debugger and see it get stuck in the while. I also have a scope probe on the TX pin and never see anything.

I am including the stm32f4xx_usart.c driver into the project.

Thanks!

#rs232-uart-usart-f4discover-407 #uart #stm32f4discovery

[Tesla DeLorean]

Posted on March 26, 2012 at 16:20

Problems there with failing to enable clocks, or configure GPIO pins.

// STM32 USART1 (Tx PA.9, Rx PA.10) STM32F4 Discovery - [e-mail]
#include ''stm32f4_discovery.h''
/**************************************************************************************/
void RCC_Configuration(void)
{
/* --------------------------- System Clocks Configuration -----------------*/
/* USART1 clock enable */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
/* GPIOA clock enable */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
}
/**************************************************************************************/
void GPIO_Configuration(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
/*-------------------------- GPIO Configuration ----------------------------*/
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_10;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA, &GPIO_InitStructure);
/* Connect USART pins to AF */
GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_USART1); // USART1_TX
GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_USART1); // USART1_RX
}
/**************************************************************************************/
void USART1_Configuration(void)
{
USART_InitTypeDef USART_InitStructure;
/* USARTx configuration ------------------------------------------------------*/
/* USARTx configured as follow:
- BaudRate = 9600 baud
- Word Length = 8 Bits
- One Stop Bit
- No parity
- Hardware flow control disabled (RTS and CTS signals)
- Receive and transmit enabled
*/
USART_InitStructure.USART_BaudRate = 9600;
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_None;
USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
USART_Init(USART1, &USART_InitStructure);
USART_Cmd(USART1, ENABLE);
}
/**************************************************************************************/
int main(void)
{
RCC_Configuration();
GPIO_Configuration();
USART1_Configuration();
while(1)
{
while(USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET); // Wait for Empty
USART_SendData(USART1, 0x49); // Send 'I'
}
while(1); // Don't want to exit
}

[chrispadbury]

Posted on March 26, 2012 at 16:43

Thanks for this, I didn't think you'd have to configure the GPIO if you were using just the UART (i.e. truning on the UART functionality I presumed would turn off the GPIO on the same pins).

I see a very gruesome trace out of PA9:

I get the same track with either the MAX3232 chip connected or not. The PC interprets it a E9 (233).

[Tesla DeLorean]

Posted on March 26, 2012 at 16:58

Dunno, is USART1 viable on the STM32F4 Discovery on these pins? Check the schematic.

Always assume the hardware isn't going to magically configure itself. Review some of the peripheral examples to get a feeling for how it's done, the API documentation mostly describes the functions, the reference manuals are the best place to understand the hardware. I've been using USART3, I had to mod this example to get you USART1. Here's a build using PB6,7 as the USART1 pins

// STM32 USART1 (Tx PB.6, Rx PB.7) STM32F4 Discovery - [e-mail]
#include ''stm32f4_discovery.h''
/**************************************************************************************/
void RCC_Configuration(void)
{
/* --------------------------- System Clocks Configuration -----------------*/
/* USART1 clock enable */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
/* GPIOB clock enable */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);
}
/**************************************************************************************/
void GPIO_Configuration(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
/*-------------------------- GPIO Configuration ----------------------------*/
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOB, &GPIO_InitStructure);
/* Connect USART pins to AF */
GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_USART1); // USART1_TX
GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_USART1); // USART1_RX
}
/**************************************************************************************/
void USART1_Configuration(void)
{
USART_InitTypeDef USART_InitStructure;
/* USARTx configuration ------------------------------------------------------*/
/* USARTx configured as follow:
- BaudRate = 9600 baud
- Word Length = 8 Bits
- One Stop Bit
- No parity
- Hardware flow control disabled (RTS and CTS signals)
- Receive and transmit enabled
*/
USART_InitStructure.USART_BaudRate = 9600;
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_None;
USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
USART_Init(USART1, &USART_InitStructure);
USART_Cmd(USART1, ENABLE);
}
/**************************************************************************************/
int main(void)
{
RCC_Configuration();
GPIO_Configuration();
USART1_Configuration();
while(1)
{
while(USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET); // Wait for Empty
USART_SendData(USART1, 0x49); // Send 'I'
}
while(1); // Don't want to exit
}

[chrispadbury]

Posted on March 26, 2012 at 17:22

It works with the alternate pins (PB6 as TX). PA9 is connected to an LED which is why it is capacitively slowed and creates a nasty trace (might work at 1200baud :-).

Thank you for your help!

[danielczigany9]

Posted on March 27, 2012 at 09:29

Hello,

you can see on STMF4 Discovery user manual (page 34): on the PA9 there is a 4.7uF capacitor. If you want to use UART1 TX then you must remove this component and you must care about PC0, you must keep it HIGH.

I suggest use UART6, the pins for UART6 is near to UART1 on the header. (PC6 Tx, PC7 Rx).

cd334

[chrispadbury]

Posted on March 27, 2012 at 12:59

Hi

I am now trying to use PortE GPIO output, but it isn't doing as expected.

// STM32 USART1 (Tx PB.6, Rx PB.7) STM32F4 Discovery - [e-mail] 
#include ''stm32f4_discovery.h'' 
void Delay(int ms); 
/**************************************************************************************/ 
void RCC_Configuration(void) 
{ 
/* --------------------------- System Clocks Configuration -----------------*/ 
/* USART1 clock enable */ 
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE); 
/* GPIOB clock enable */ 
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE); 
} 
/**************************************************************************************/ 
void GPIO_Configuration(void) 
{ 
GPIO_InitTypeDef GPIO_InitStructure; 
/*-------------------------- GPIO Configuration ----------------------------*/ 
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7; 
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF; 
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; 
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL; 
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; 
GPIO_Init(GPIOB, &GPIO_InitStructure); 
/* Connect USART pins to AF */ 
GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_USART1); // USART1_TX 
GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_USART1); // USART1_RX 
// Configure Port E : Pins 7-15 as outputs 
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7 | GPIO_Pin_8 | GPIO_Pin_9 | GPIO_Pin_10 | GPIO_Pin_11 | GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15; 
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT; 
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; 
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP; 
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; 
GPIO_Init(GPIOE, &GPIO_InitStructure); 
} 
/**************************************************************************************/ 
void USART1_Configuration(void) 
{ 
USART_InitTypeDef USART_InitStructure; 
/* USARTx configuration ------------------------------------------------------*/ 
/* USARTx configured as follow: 
- BaudRate = 9600 baud 
- Word Length = 8 Bits 
- One Stop Bit 
- No parity 
- Hardware flow control disabled (RTS and CTS signals) 
- Receive and transmit enabled 
*/ 
USART_InitStructure.USART_BaudRate = 9600; 
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_None; 
USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx; 
USART_Init(USART1, &USART_InitStructure); 
USART_Cmd(USART1, ENABLE); 
} 
/**************************************************************************************/ 
int main(void) 
{ 
int i; 
char c; 
RCC_Configuration(); 
GPIO_Configuration(); 
USART1_Configuration(); 
i = 30; 
while(i--) { 
while(USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET); // Wait for Empty 
USART_SendData(USART1, 0x49); // Send 'I' 
//Load the byte onto pins 8-15 of Port E 
//reset all 8 pins 
GPIO_ResetBits(GPIOE, GPIO_Pin_8 | GPIO_Pin_9 | GPIO_Pin_10 | GPIO_Pin_11 | GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15); 
c = i; 
if(c & 0x01) { 
GPIO_SetBits(GPIOE, GPIO_Pin_8); 
} 
if(c & 0x02) { 
GPIO_SetBits(GPIOE, GPIO_Pin_9); 
} 
if(c & 0x04) { 
GPIO_SetBits(GPIOE, GPIO_Pin_10); 
} 
if(c & 0x08) { 
GPIO_SetBits(GPIOE, GPIO_Pin_11); 
} 
if(c & 0x10) { 
GPIO_SetBits(GPIOE, GPIO_Pin_12); 
} 
if(c & 0x20) { 
GPIO_SetBits(GPIOE, GPIO_Pin_13); 
} 
if(c & 0x40) { 
GPIO_SetBits(GPIOE, GPIO_Pin_14); 
} 
if(c & 0x80) { 
GPIO_SetBits(GPIOE, GPIO_Pin_15); 
} 
GPIO_SetBits(GPIOE, GPIO_Pin_7); 
Delay(500); 
GPIO_ResetBits(GPIOE, GPIO_Pin_7); 
Delay(500); 
} 
while(1); // Don't want to exit 
} 
void Delay(int ms) { 
ms = ms * 168000 / 4; 
while (ms) { 
ms--; 
} 
} 

I see the I characters coming out of the RS232 but never see anything on PortE pin7 (or pins 8-15 for that matter). PortE_7 seems to be behaving like an input as well because if I connect it to a different board with a pin configured as an input but with pull-up, PortE_7 follows it to high.

[chrispadbury]

Posted on March 27, 2012 at 13:02

Note: it is a while(1) as the last line of code not just while().

[Tesla DeLorean]

Posted on March 27, 2012 at 16:00

/* GPIOE clock enable */ 
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE, ENABLE); 

[chrispadbury]

Posted on March 27, 2012 at 16:50

Sorry, should have spotted that.

Thanks for your help.

[chrispadbury]

Posted on March 28, 2012 at 17:54

Out of interest, Is there a more elegant way to write to the upper 8 pins of portE. I am more used to eight bit micros, where it is simpler dealing with single bytes all the time.