Getting garbage over USART1

[mcdowell]

Posted on March 29, 2011 at 19:03

Hi 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]

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 Philippe

Hi 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

[christianfaurebouvard9]

Posted on May 31, 2011 at 15:38

Hi,

i'm not sure, but you may need a level shifter between  stm8l-discovery and PC port?