USART on STM32F4 using Arduino board

Question

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 · Answer

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 voidDelay(__IO uint32_t nCount);voidUART_Initialize(void);voidGPIOInitialize(void);voidNVICInitialize(void);voidUSART_puts( volatile char*s);USART_InitTypeDef USART_InitStructure;GPIO_InitTypeDef GPIO_InitStructure;NVIC_InitTypeDef NVIC_InitStructure;intmain(void){GPIOInitialize();UART_Initialize();NVICInitialize();//USART_puts(''B'');while(1) {/* Variable gérant le ''spinner'' */unsigned charspin = 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); // LSBGPIO_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) */voidDelay(__IO uint32_t nCount) {while(nCount--);}voidUART_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 configurationUSART_Cmd(USART1, ENABLE); // Enable USART}voidGPIOInitialize(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); // LedRCC_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, LED6GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT; // Broches en sortieGPIO_InitStructure.GPIO_OType = GPIO_OType_PP; // Mode PushPullGPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; // Fréquence de commutation maximumGPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL; // Pas de résistance de pull-up / pull-downGPIO_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_TxGPIO_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 entréeGPIO_InitStructure.GPIO_OType = GPIO_OType_PP; // Mode PushPullGPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; // Fréquence de commutation maximumGPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL; // Pas de résistance de pull-up / pull-downGPIO_Init(GPIOA, &GPIO_InitStructure);}voidNVICInitialize(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);}/*voidUSART_puts(volatile char*s){while(*s){// wait until data register is emptywhile( !(USART1->SR & 0x00000040) );USART_SendData(USART1, *s);*s++;}}*/#ifdef USE_FULL_ASSERTvoidassert_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

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