STM32429I-EVAL Can't get higher data rate than 1 megabit over USART.

[thomas2]

Posted on May 14, 2014 at 11:29

I've tried porting the stm32cubef4UART DMA example to use USART, but I still can't achieve faster speeds than 1 megabit. The MCU can apparently support speeds of up to 11 megabits, am I simply asking too much of the peripheral? My output essentially becomes random letters.

My configuration is as such: Main:

int
main(
void
)
{ 
/* STM32F4xx HAL library initialization:
- Configure the Flash prefetch, instruction and Data caches
- Configure the Systick to generate an interrupt each 1 msec
- Set NVIC Group Priority to 4
- Global MSP (MCU Support Package) initialization
*/
HAL_Init();
/* Configure the system clock to 180 Mhz */
SystemClock_Config();
/* Configure LED1, LED2 and LED3 */
BSP_LED_Init(LED1);
BSP_LED_Init(LED2);
BSP_LED_Init(LED3);
/*##-1- Configure the UART peripheral ######################################*/
/* Put the USART peripheral in the Asynchronous mode (UART Mode) */
/* UART1 configured as follow:
- Word Length = 8 Bits
- Stop Bit = One Stop bit
- Parity = ODD parity
- BaudRate = 9600 baud
- Hardware flow control disabled (RTS and CTS signals) */
UsartHandle.Instance = USARTx;
UsartHandle.Init.BaudRate = 1048576;
UsartHandle.Init.WordLength = USART_WORDLENGTH_8B;
UsartHandle.Init.StopBits = USART_STOPBITS_1;
UsartHandle.Init.Parity = USART_PARITY_NONE;
//UsartHandle.Init.HwFlowCtl = UART_HWCONTROL_NONE;
UsartHandle.Init.Mode = USART_MODE_TX;
UsartHandle.Init.CLKLastBit = USART_LASTBIT_DISABLE;
UsartHandle.Init.CLKPhase = USART_PHASE_1EDGE;
UsartHandle.Init.CLKPolarity = USART_POLARITY_LOW;
if
(HAL_USART_Init(&UsartHandle) != HAL_OK)
{
/* Initialization Error */
Error_Handler(); 
}
//Spam messages over serial.
while
(1)
{
/*##-2- Start the transmission process #####################################*/
/* User start transmission data through ''TxBuffer'' buffer */
if
(HAL_USART_Transmit_DMA(&UsartHandle, (uint8_t*)aTxBuffer, TXBUFFERSIZE)!= HAL_OK)
{
/* Transfer error in transmission process */
Error_Handler(); 
}
while
(HAL_USART_GetState(&UsartHandle) != HAL_USART_STATE_READY)
{
} 
}
}

Clock setup:

static
void
SystemClock_Config(
void
)
{
RCC_ClkInitTypeDef RCC_ClkInitStruct;
RCC_OscInitTypeDef RCC_OscInitStruct;
/* Enable Power Control clock */
__PWR_CLK_ENABLE();
/* The voltage scaling allows optimizing the power consumption when the device is 
clocked below the maximum system frequency, to update the voltage scaling value 
regarding system frequency refer to product datasheet. */
__HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);
/* Enable HSE Oscillator and activate PLL with HSE as source */
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
RCC_OscInitStruct.HSEState = RCC_HSE_ON;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
RCC_OscInitStruct.PLL.PLLM = 25;
RCC_OscInitStruct.PLL.PLLN = 360;
RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
RCC_OscInitStruct.PLL.PLLQ = 7;
HAL_RCC_OscConfig(&RCC_OscInitStruct);
HAL_PWREx_ActivateOverDrive();
/* Select PLL as system clock source and configure the HCLK, PCLK1 and PCLK2 
clocks dividers */
RCC_ClkInitStruct.ClockType = (RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2);
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4; 
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2; 
HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5);
}

USART MSP Init:

void
HAL_USART_MspInit(USART_HandleTypeDef *husart)
{
static
DMA_HandleTypeDef hdma_tx;
static
DMA_HandleTypeDef hdma_rx;
GPIO_InitTypeDef GPIO_InitStruct;
/*##-1- Enable peripherals and GPIO Clocks #################################*/
/* Enable GPIO clock */
USARTx_TX_GPIO_CLK_ENABLE();
USARTx_RX_GPIO_CLK_ENABLE();
/* Enable USART1 clock */
USARTx_CLK_ENABLE(); 
/* Enable DMA2 clock */
DMAx_CLK_ENABLE(); 
/*##-2- Configure peripheral GPIO ##########################################*/
/* UART TX GPIO pin configuration */
GPIO_InitStruct.Pin = GPIO_PIN_10|GPIO_PIN_9|GPIO_PIN_8;
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_LOW;
GPIO_InitStruct.Alternate = GPIO_AF7_USART1;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
/*##-3- Configure the DMA streams ##########################################*/
/* Configure the DMA handler for Transmission process */
hdma_tx.Instance = USARTx_TX_DMA_STREAM;
hdma_tx.Init.Channel = USARTx_TX_DMA_CHANNEL;
hdma_tx.Init.Direction = DMA_MEMORY_TO_PERIPH;
hdma_tx.Init.PeriphInc = DMA_PINC_DISABLE;
hdma_tx.Init.MemInc = DMA_MINC_ENABLE;
hdma_tx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
hdma_tx.Init.MemDataAlignment = DMA_MDATAALIGN_BYTE;
hdma_tx.Init.Mode = DMA_NORMAL;
hdma_tx.Init.Priority = DMA_PRIORITY_LOW;
hdma_tx.Init.FIFOMode = DMA_FIFOMODE_DISABLE; 
hdma_tx.Init.FIFOThreshold = DMA_FIFO_THRESHOLD_FULL;
hdma_tx.Init.MemBurst = DMA_MBURST_INC4;
hdma_tx.Init.PeriphBurst = DMA_PBURST_INC4;
HAL_DMA_Init(&hdma_tx); 
/* Associate the initialized DMA handle to the UART handle */
__HAL_LINKDMA(husart, hdmatx, hdma_tx);
/* Configure the DMA handler for reception process */
hdma_rx.Instance = USARTx_RX_DMA_STREAM;
hdma_rx.Init.Channel = USARTx_RX_DMA_CHANNEL;
hdma_rx.Init.Direction = DMA_PERIPH_TO_MEMORY;
hdma_rx.Init.PeriphInc = DMA_PINC_DISABLE;
hdma_rx.Init.MemInc = DMA_MINC_ENABLE;
hdma_rx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
hdma_rx.Init.MemDataAlignment = DMA_MDATAALIGN_BYTE;
hdma_rx.Init.Mode = DMA_NORMAL;
hdma_rx.Init.Priority = DMA_PRIORITY_HIGH;
hdma_rx.Init.FIFOMode = DMA_FIFOMODE_DISABLE; 
hdma_rx.Init.FIFOThreshold = DMA_FIFO_THRESHOLD_FULL;
hdma_rx.Init.MemBurst = DMA_MBURST_INC4;
hdma_rx.Init.PeriphBurst = DMA_PBURST_INC4; 
HAL_DMA_Init(&hdma_rx);
/* Associate the initialized DMA handle to the the UART handle */
__HAL_LINKDMA(husart, hdmarx, hdma_rx);
/*##-4- Configure the NVIC for DMA #########################################*/
/* NVIC configuration for DMA transfer complete interrupt (USART1_TX) */
HAL_NVIC_SetPriority(USARTx_DMA_TX_IRQn, 0, 1);
HAL_NVIC_EnableIRQ(USARTx_DMA_TX_IRQn);
/* NVIC configuration for DMA transfer complete interrupt (USART1_RX) */
HAL_NVIC_SetPriority(USARTx_DMA_RX_IRQn, 0, 0); 
HAL_NVIC_EnableIRQ(USARTx_DMA_RX_IRQn);
}

Am I missing anything obvious? Any help would be appreciated. Thanks in advance. #stm32429i-eval-usart

[waclawek.jan]

Posted on May 14, 2014 at 12:42

Did you calculate the bit duration error? What is the receiver, is it capable to receive the given baudrate?  And what is your hardware used to connect to the receiver?

JW

[Tesla DeLorean]

Posted on May 14, 2014 at 12:44

Am I missing anything obvious? Any help would be appreciated. Thanks in advance.

What's the maximum bandwidth of RS232 level shifters? What do the signals look like on a scope?

[thomas2]

Posted on May 14, 2014 at 13:01

Hi thanks for the reply. What exactly do you mean by bit duration error? I'm using linux with minicom to receive the serial, which can accept baudrates of over 1 megabit. (Windows appears to cap it at that). I'm using a simple serial to USB adapter. Thanks in advance.

[Tesla DeLorean]

Posted on May 14, 2014 at 13:14

http://waijung.aimagin.com/st3241eb_datasheet.pdf

- ''±15 kV ESD protected 3 to 5.5 V, 400 kbps, RS-232 transceiver with auto-power-down'' ''The device is guaranteed to run at data rates of 250 kbps while maintaining RS-232 output levels.''

[waclawek.jan]

Posted on May 14, 2014 at 13:19

> What exactly do you mean by bit duration error?

The difference between the desired bit duration, and the real duration, given by rounding of the baudrate divider. > I'm using linux with minicom to receive the serial, which can accept baudrates of over 1 megabit. (Windows appears to cap it at that). I'm using a simple serial to USB adapter. Is that ''simple serial to USB adapter'' capable of receiving the desired baudrate? Again, there are errors involved. You may enter a number in minicom, but it does not mean the receiver actually works at that baudrate. JW

[thomas2]

Posted on May 14, 2014 at 15:36

Thanks. Looks like i'll choose another protocol for my application. Most likely Ethernet. 

[Tesla DeLorean]

Posted on May 14, 2014 at 16:01

Thanks. Looks like i'll choose another protocol for my application. Most likely Ethernet. 

Well probably a smart plan, asynchronous serial is ill suited to high rates, which is why we have USB and ETHERNET type standards.