Getting garbage over USART1

Question

Posted on March 29, 2011 at 19:03Hi All, I have taken some of the sample code that comes with the stm8l-discovery eval board to try and talk to hyperterm on from stm8.  when i try to send anything all I see is garbage on the hyperterm screen...  I have verified both side have the same settings, 115200, no polarity, 1 stop bit, 8 bit word length - butstill it does not work. Can I get some help to get this working?  My sample code snippet is as follows - can someone explain what I am doing wrong? &sharpdefine DBG_COM1                   USART1 &sharpdefine DBG_COM1_GPIO              GPIOC &sharpdefine DBG_COM1_CLK               CLK_Peripheral_USART1 &sharpdefine DBG_COM1_RxPin             GPIO_Pin_2 &sharpdefine DBG_COM1_TxPin             GPIO_Pin_3 &sharpdefine DBG_COM1_ClkPin            GPIO_Pin_4 typedef enum {    COM1 = 0 } COM_TypeDef; USART_TypeDef* COM_USART[COMn] = {     DBG_COM1 };   GPIO_TypeDef* COM_PORT[COMn] = {     DBG_COM1_GPIO }; const uint8_t COM_USART_CLK[COMn] = {     DBG_COM1_CLK }; const uint8_t COM_TX_PIN[COMn] = {     DBG_COM1_TxPin }; const uint8_t COM_RX_PIN[COMn] = {     DBG_COM1_RxPin }; const uint8_t COM_CLK_PIN[COMn] = {     DBG_COM1_ClkPin }; static void COMInit(COM_TypeDef COM, uint32_t USART_BaudRate,                        USART_WordLength_TypeDef USART_WordLength,                        USART_StopBits_TypeDef USART_StopBits,                        USART_Parity_TypeDef USART_Parity,                        USART_Mode_TypeDef USART_Mode) {     USART_DeInit(COM_USART[COM]);    /* Enable USART clock */    CLK_PeripheralClockConfig((CLK_Peripheral_TypeDef)COM_USART_CLK[COM], ENABLE);      /* Configure USART Tx as alternate function push-pull  (software pull up)*/    GPIO_ExternalPullUpConfig(COM_PORT[COM], COM_TX_PIN[COM] | COM_RX_PIN[COM] , ENABLE);      /* USART configuration */    USART_Init(COM_USART[COM], USART_BaudRate,               USART_WordLength,               USART_StopBits,               USART_Parity,               USART_Mode); } main() { ...    COMInit(COM1, (uint32_t)115200, USART_WordLength_8b, USART_StopBits_1,                     USART_Parity_No, USART_Mode_Tx | USART_Mode_Rx);              USART_Cmd(COM_USART[COM1], ENABLE);      //try to send a few bytes to hyperterm    USART_SendData8(DBG_COM1, 0x41);    while (USART_GetFlagStatus(DBG_COM1, USART_FLAG_TC) == RESET);    USART_SendData8(DBG_COM1, 0x42);    while (USART_GetFlagStatus(DBG_COM1, USART_FLAG_TC) == RESET); ... when i do these writes all I see is garbage on PC hyperterm screen... My h/w setup is as follows: PC2 pin jumpered to TX on DB9 connector PC3 pin jumpered to RX on DB9 connector #usart-rs232

vincent.philippe · Answer

Posted on April 06, 2011 at 10:24 Hi, If you see garbage, I think that you have perhaps baud rate problems. In first I will check the baud rate initialization.In fact, if you check in the driver functions the baud rate frequency depends of CPU clock frequency. I can suggest to you to check if these points: > Check which clock is used in your application (LSI, HSI, ...); > Check the CPU clock frequency; > Check in USART register the values setted; This is the first way .... Other points, questions: > In you application do you send the caracters one by one (place one break point after the first caracter is sent ( line: while( ....) ) and check it.? > Have you try the reception from hyperterminal? I hope that these points can help you. Best regards PhilippeHi All, I have taken some of the sample code that comes with the stm8l-discovery eval board to try and talk to hyperterm on from stm8.  when i try to send anything all I see is garbage on the hyperterm screen...  I have verified both side have the same settings, 115200, no polarity, 1 stop bit, 8 bit word length - butstill it does not work. Can I get some help to get this working?  My sample code snippet is as follows - can someone explain what I am doing wrong? #define DBG_COM1                   USART1 #define DBG_COM1_GPIO              GPIOC #define DBG_COM1_CLK               CLK_Peripheral_USART1 #define DBG_COM1_RxPin             GPIO_Pin_2 #define DBG_COM1_TxPin             GPIO_Pin_3 #define DBG_COM1_ClkPin            GPIO_Pin_4 typedef enum {    COM1 = 0 } COM_TypeDef; USART_TypeDef* COM_USART[COMn] = {     DBG_COM1 };   GPIO_TypeDef* COM_PORT[COMn] = {     DBG_COM1_GPIO }; const uint8_t COM_USART_CLK[COMn] = {     DBG_COM1_CLK }; const uint8_t COM_TX_PIN[COMn] = {     DBG_COM1_TxPin }; const uint8_t COM_RX_PIN[COMn] = {     DBG_COM1_RxPin }; const uint8_t COM_CLK_PIN[COMn] = {     DBG_COM1_ClkPin }; static void COMInit(COM_TypeDef COM, uint32_t USART_BaudRate,                        USART_WordLength_TypeDef USART_WordLength,                        USART_StopBits_TypeDef USART_StopBits,                        USART_Parity_TypeDef USART_Parity,                        USART_Mode_TypeDef USART_Mode) {     USART_DeInit(COM_USART[COM]);    /* Enable USART clock */    CLK_PeripheralClockConfig((CLK_Peripheral_TypeDef)COM_USART_CLK[COM], ENABLE);      /* Configure USART Tx as alternate function push-pull  (software pull up)*/    GPIO_ExternalPullUpConfig(COM_PORT[COM], COM_TX_PIN[COM] | COM_RX_PIN[COM] , ENABLE);      /* USART configuration */    USART_Init(COM_USART[COM], USART_BaudRate,               USART_WordLength,               USART_StopBits,               USART_Parity,               USART_Mode); } main() { ...    COMInit(COM1, (uint32_t)115200, USART_WordLength_8b, USART_StopBits_1,                     USART_Parity_No, USART_Mode_Tx | USART_Mode_Rx);              USART_Cmd(COM_USART[COM1], ENABLE);      //try to send a few bytes to hyperterm    USART_SendData8(DBG_COM1, 0x41);    while (USART_GetFlagStatus(DBG_COM1, USART_FLAG_TC) == RESET);    USART_SendData8(DBG_COM1, 0x42);    while (USART_GetFlagStatus(DBG_COM1, USART_FLAG_TC) == RESET); ... when i do these writes all I see is garbage on PC hyperterm screen... My h/w setup is as follows: PC2 pin jumpered to TX on DB9 connector PC3 pin jumpered to RX on DB9 connector

Sign up

Login with SSO

Login to the community

Login with SSO

Scanning file for viruses.

This file cannot be downloaded