USART on STM32F4 using Arduino board

[ed_62]

Posted on August 21, 2015 at 00:28

NOTE: edited by moderator on Oct 6th, 2016

Hello everyone,

I just received my stm32f4 discovery board yesterday and it works well :). I managed to run a LED blinking example. I now want to display some results in a serial communication. I am trying to interface an Arduino Uno with my stm board. I found an example on the internet :

[[this link/image has been flagged as malicious by our security scan software and has been deleted]]

but I am not able to make it works properly.

I put wires between TX of Arduino- PB7 and RX of Arduino - PB6. Here is my Arduino code :

#include <SoftwareSerial.h>
SoftwareSerial gprsSerial(0, 1);
void
setup() {
// initialize serial communication at 9600 bits per second:
gprsSerial.begin(9600);
Serial.begin(9600);
}
/* Loop() */
void
loop() { 
// Si des données sont disponible en lecture
if
(gprsSerial.available() > 0) {
// Lecture d'un octet depuis le port série
int

 c = gprsSerial.read();
Serial.println(c);}
}

When I click on the reset button of the stm board, I receive these 4 numbers on the Arduinoterminal : 255;28;0;252 I don't know how to deal with these numbers. It represents Byte but what is the relation ? Moreover, If I change the sentence to display.

USART_puts(
''b''
);

I still have 4 numbers : 255;224;0;252

Do you know what it means ? Normally, I should receive more numbers for the sentence than the char. Thank you very much for your help.

[ed_62]

Posted on August 23, 2015 at 20:54

NOTE: edited by moderator on Oct 6th, 2016

I have modified the way I dot it. I linked the pin Reset with the Ground of the Arduino board. So I directly receive the data from the STM32 without writing any code on the Arduino board. But it still doesn't work ... I use this terminal application :

https://sites.google.com/site/terminalbpp/

Here is my code :

#include ''stm32f4xx.h''
#include ''stm32f4xx_gpio.h''
#include ''stm32f4xx_rcc.h''
#include ''stm32f4xx_usart.h''
#include ''misc.h''
inline 
void
Delay(__IO uint32_t nCount);
void
UART_Initialize(
void
);
void
GPIOInitialize(
void
);
void
NVICInitialize(
void
);
void
USART_puts( volatile 
char
*s);
USART_InitTypeDef USART_InitStructure;
GPIO_InitTypeDef GPIO_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
int
main(
void
)
{
GPIOInitialize();
UART_Initialize();
NVICInitialize();
//USART_puts(''B'');
while
(1) {
/* Variable gérant le ''spinner'' */
unsigned 
char
spin = 1;
/* Boucle infini */
for
(;;) {
/* Lecture de l'état du bouton, si appuyé on entre dans le if */
if
(GPIO_ReadInputDataBit(GPIOA, GPIO_Pin_0)) {
USART_SendData(USART1, 'A');
/* ''Ecrit'' les états des led en fonction du spinner (4 bits) */
GPIO_WriteBit(GPIOD, GPIO_Pin_12, (spin & 1) ? 1 : 0); 
// LSB
GPIO_WriteBit(GPIOD, GPIO_Pin_13, (spin & 2) ? 1 : 0); 
//
GPIO_WriteBit(GPIOD, GPIO_Pin_14, (spin & 4) ? 1 : 0); 
//
GPIO_WriteBit(GPIOD, GPIO_Pin_15, (spin & 8) ? 1 : 0); 
// MSB
/* Delai (~1sec en gros) */
Delay(0x3FFFFF);
/* Rotation du ''spinner'' d'un cran */
spin = (spin << 1) & 0x0f;
/* Si le ''spinner'' a dépassé la valeur max : retour au début */
if
(spin == 0)
spin = 1;
}
}
}
}
/* Fonction de delai (trés grossiére) */
void
Delay(__IO uint32_t nCount) {
while
(nCount--)
;
}
void
UART_Initialize(
void
)
{
/* Enable peripheral clock for USART1 */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
/* USART1 configured as follow:
* BaudRate 9600 baud
* Word Length 8 Bits
* 1 Stop Bit
* No parity
* Hardware flow control disabled
* 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 configuration
USART_Cmd(USART1, ENABLE); 
// Enable USART
}
void
GPIOInitialize(
void
)
{
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE); 
//Enable clock for GPIOB
/* Structure permettant de stocker la configuration d'une ou plusieurs broches */
GPIO_InitTypeDef GPIO_InitStructure;
/* Mise en marche des horloge gérant les ports D (led) et A (bouton) */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE); 
// Led
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE); 
// Button
/* Configuration de LED3, LED4, LED5, LED6 en sortie de type ''pushpull'' (mode classique) */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15; 
// LED3, LED4, LED5, LED6
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT; 
// Broches en sortie
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; 
// Mode PushPull
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; 
// Fréquence de commutation maximum
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL; 
// Pas de résistance de pull-up / pull-down
GPIO_Init(GPIOD, &GPIO_InitStructure);
/* USART1 Tx on PB6 | Rx on PB7 */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(GPIOB, &GPIO_InitStructure);
GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_USART1);
//Connect PB6 to USART1_Tx
GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_USART1);
//Connect PB7 to USART1_Rx
/* Configuration du bouton ''User'' en entrée de type ''pushpull'' (mode classique) */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0; 
// Bouton ''User''
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;
// Broches en entrée
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; 
// Mode PushPull
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; 
// Fréquence de commutation maximum
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL; 
// Pas de résistance de pull-up / pull-down
GPIO_Init(GPIOA, &GPIO_InitStructure);
}
void
NVICInitialize(
void
)
{
NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);
}
/*void
USART_puts(volatile 
char
*s){
while
(*s){
// wait until data register is empty
while
( !(USART1->SR & 0x00000040) );
USART_SendData(USART1, *s);
*s++;
}
}*/
#ifdef USE_FULL_ASSERT
void
assert_failed(uint8_t* file, uint32_t line)
{
while
(1)
{}
}
#endif

I am receiving these characters on the terminal : <0>ü I tried to change the sending characters but I still receive these kinds of characters : à, û, ü, <0>... All the parameters seem to be corrects. Do you have an idea ofhow to solve this problem ? There is something which is surprising. IfI connect PB6 ( Tx of STM32) to Rx of Arduino board, I receive nothing on the terminal. i have to connect PB6 to TX of Arduino to make It works... Thank you in advance for your help. ________________ Attachments : Terminal.png : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006I0bn&d=%2Fa%2F0X0000000bbA%2FncDuLsE36UDUPsZk6lD2uBMuXLROR2o2Wp5G9JX3paU&asPdf=false

[Tesla DeLorean]

Posted on August 23, 2015 at 22:27

NOTE: edited by moderator on Oct 6th, 2016

The serial outputs from the STM32 are CMOS levels, RS232 compatible ones.

The STM32F4-DISCO uses an 8 MHz clock source, not a 25 MHz one, make sure the PLL settings are for the right clock source, and that the HSE_VALUE define matches the clock being used. Makes sure to check TXE before writing data to the port, and check RXNE before reading.