USART DMA Rx for ESP8266 module

[RomainR.]

Posted on August 03, 2016 at 10:48

Hi All,

Well, I started playing with a ESP8266-01 module with the latest firmware AT Expressive. Now I did communicate a STM32L476 (UART 115200 which is the default baud rate of ESP8266). I use a code generated by IAR Cube HAL Drivers. I configured my project with USART1 RX DMA circular mode. I wrote a SendATCommand () function works properly. And a large variable rxBuffer [] to read the DMA. I correctly get responses rxBuffer module ['A', 'T', '\ r', '\ r', '\ n', '\ r', '\ n', 'O', 'K' , \ r \ n ') for example an AT command \ r \ n Now how can I handle the DMA buffer data (ie OK or ready Rx command) ? Thank you in advance for your assistance.

/* Includes ------------------------------------------------------------------*/
#include ''stm32l4xx_hal.h''
#include <stdio.h>
#include <string.h>
#include <stdbool.h>
#define BUFFER_SIZE 32
#ifdef __GNUC__
/* With GCC/RAISONANCE, small printf (option LD Linker->Libraries->Small printf
set to 'Yes') calls __io_putchar() */
#define PUTCHAR_PROTOTYPE int __io_putchar(int ch)
#else
#define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f)
#endif /* __GNUC__ */
/* Private variables ---------------------------------------------------------*/
UART_HandleTypeDef huart1;
UART_HandleTypeDef huart2;
DMA_HandleTypeDef hdma_usart1_rx;
/* Private variables ---------------------------------------------------------*/
uint8_t rxBuffer[BUFFER_SIZE];
char
esp8266_reset[] = 
''AT+RST\r\n''
;
char
esp8266_AT[] = 
''AT\r\n''
;
char
esp8266_CWMODE1[] = 
''AT+CWMODE=1\r\n''
;
char
esp8266_CWMODE2[] = 
''AT+CWMODE=2\r\n''
;
char
esp8266_CWMODE3[] = 
''AT+CWMODE=3\r\n''
;
int
main(
void
)
{
/* Reset of all peripherals, Initializes the Flash interface and the Systick. */
HAL_Init();
/* Configure the system clock 24MHz HSI + PLL */
SystemClock_Config();
/* Initialize all configured peripherals */
MX_GPIO_Init();
MX_DMA_Init();
MX_USART2_UART_Init();
MX_USART1_UART_Init();
HAL_UART_Receive_DMA(&huart1, rxBuffer, BUFFER_SIZE);
HAL_UART_DMAPause(&huart1);
esp_Reset();
HAL_Delay(1000);
printf
(
''ESP Module HW Reset Done\r\n''
);
/* Send Reset AT command */
send_ATCommand(esp8266_reset, 1000);
HAL_Delay(1000);
printf
(
''Send AT cmd AT+RST\r\n''
);
HAL_UART_DMAResume(&huart1);
/* Infinite loop */
while
(1)
{
/* Wait for user Button is pressed and released */
while
(HAL_GPIO_ReadPin(GPIOC, GPIO_PIN_13) != GPIO_PIN_RESET);
while
(HAL_GPIO_ReadPin(GPIOC, GPIO_PIN_13) != GPIO_PIN_SET);
send_ATCommand(esp8266_AT, 1000);
printf
(
''Send AT cmd AT\r\n''
);
}
}
/* USART1 init function */
static
void
MX_USART1_UART_Init(
void
)
{
huart1.Instance = USART1;
huart1.Init.BaudRate = 115200;
huart1.Init.WordLength = UART_WORDLENGTH_8B;
huart1.Init.StopBits = UART_STOPBITS_1;
huart1.Init.Parity = UART_PARITY_NONE;
huart1.Init.Mode = UART_MODE_TX_RX;
huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
huart1.Init.OverSampling = UART_OVERSAMPLING_16;
huart1.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
huart1.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
if
(HAL_UART_Init(&huart1) != HAL_OK)
{
Error_Handler();
}
}
/* USART2 init function */
static
void
MX_USART2_UART_Init(
void
)
{
huart2.Instance = USART2;
huart2.Init.BaudRate = 115200;
huart2.Init.WordLength = UART_WORDLENGTH_8B;
huart2.Init.StopBits = UART_STOPBITS_1;
huart2.Init.Parity = UART_PARITY_NONE;
huart2.Init.Mode = UART_MODE_TX_RX;
huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
huart2.Init.OverSampling = UART_OVERSAMPLING_16;
huart2.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
huart2.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
if
(HAL_UART_Init(&huart2) != HAL_OK)
{
Error_Handler();
}
}
/** 
* Enable DMA controller clock
*/
static
void
MX_DMA_Init(
void
) 
{
/* DMA controller clock enable */
__HAL_RCC_DMA1_CLK_ENABLE();
/* DMA interrupt init */
/* DMA1_Channel5_IRQn interrupt configuration */
HAL_NVIC_SetPriority(DMA1_Channel5_IRQn, 1, 0);
HAL_NVIC_EnableIRQ(DMA1_Channel5_IRQn);
}
/**
* @brief Retargets the C library printf function to the USART.
* @param None
* @retval None
*/
PUTCHAR_PROTOTYPE
{
/* Place your implementation of fputc here */
/* e.g. write a character to the EVAL_COM1 and Loop until the end of transmission */
HAL_UART_Transmit(&huart2, (uint8_t *)&ch, 1, 0xFFFF); 
return
ch;
}
/**
* @brief Perform a Hard RESET of ESP module
* @param None
* @retval None
*/
static
void
esp_Reset(
void
)
{
HAL_GPIO_WritePin(GPIOD, GPIO_PIN_2, GPIO_PIN_SET);
/* Reset pin go low for 200ms */
HAL_GPIO_WritePin(GPIOD, GPIO_PIN_2, GPIO_PIN_RESET);
HAL_Delay(200);
/* Reset pin go high again */
HAL_GPIO_WritePin(GPIOD, GPIO_PIN_2, GPIO_PIN_SET);
}
/**
* @brief Send an AT command string to ESP module
* @param String command
* @param Timeout in ms
* @retval None
*/
static
void
send_ATCommand(
char
*cmd, uint32_t esp_timeout)
{
if
(esp_timeout > 2000)
esp_timeout = 2000;
uint16_t cmd_len = 
strlen
(cmd);
HAL_UART_Transmit(&huart1, (uint8_t *)cmd, cmd_len, esp_timeout);
}
void
HAL_UART_MspInit(UART_HandleTypeDef* huart)
{
GPIO_InitTypeDef GPIO_InitStruct;
if
(huart->Instance==USART1)
{
/* USER CODE BEGIN USART1_MspInit 0 */
/* USER CODE END USART1_MspInit 0 */
/* Peripheral clock enable */
__HAL_RCC_USART1_CLK_ENABLE();
/**USART1 GPIO Configuration 
PB6 ------> USART1_TX
PB7 ------> USART1_RX 
*/
GPIO_InitStruct.Pin = GPIO_PIN_6|GPIO_PIN_7;
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Pull = GPIO_PULLUP;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
GPIO_InitStruct.Alternate = GPIO_AF7_USART1;
HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
/* Peripheral DMA init*/
hdma_usart1_rx.Instance = DMA1_Channel5;
hdma_usart1_rx.Init.Request = DMA_REQUEST_2;
hdma_usart1_rx.Init.Direction = DMA_PERIPH_TO_MEMORY;
hdma_usart1_rx.Init.PeriphInc = DMA_PINC_DISABLE;
hdma_usart1_rx.Init.MemInc = DMA_MINC_ENABLE;
hdma_usart1_rx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
hdma_usart1_rx.Init.MemDataAlignment = DMA_MDATAALIGN_BYTE;
hdma_usart1_rx.Init.Mode = DMA_NORMAL;
hdma_usart1_rx.Init.Priority = DMA_PRIORITY_MEDIUM;
if
(HAL_DMA_Init(&hdma_usart1_rx) != HAL_OK)
{
Error_Handler();
}
__HAL_LINKDMA(huart,hdmarx,hdma_usart1_rx);
/* USER CODE BEGIN USART1_MspInit 1 */
/* USER CODE END USART1_MspInit 1 */
}
else
if
(huart->Instance==USART2)
{
/* USER CODE BEGIN USART2_MspInit 0 */
/* USER CODE END USART2_MspInit 0 */
/* Peripheral clock enable */
__HAL_RCC_USART2_CLK_ENABLE();
/**USART2 GPIO Configuration 
PA2 ------> USART2_TX
PA3 ------> USART2_RX 
*/
GPIO_InitStruct.Pin = USART_TX_Pin|USART_RX_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
GPIO_InitStruct.Alternate = GPIO_AF7_USART2;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
}
}

#hal

[AvaTar]

Posted on August 03, 2016 at 14:45

> I configured my project with USART1 RX DMA circular mode.

IMHO not the best choice for a protocol with arbitrary-length commands. Fixed length reception (DMA or FIFO) only coincidentally (read: never) matches the command length, thus commands get stuck in the FIFO/DMA buffer, to get ''pushed through'' only by the next command. Almost impossible to get reception an processing in sync that way. I always use single-character interrupts for such protocols.

[RomainR.]

Posted on August 03, 2016 at 15:53

I always use single-character interrupts for such protocols.

Yep, that's what I'm trying to implement (USART Rx interrupt, one byte at a time)The problem is that in the response of the ESP8266, the first character is '\ n' (followed by '\ r' 'O' 'K' '\ r' '\ n', so I just wanted to detect this '\ n' to complete the handling of the packet in the Rx interrupt routine.To continue...Thank you Avatar

[AvaTar]

Posted on August 04, 2016 at 10:03

> The problem is that in the response of the ESP8266, the first character is '\ n' (followed by '\ r' 'O' 'K' '\ r' '\ n', so I just wanted to detect this '\ n' to complete the handling of the packet in the Rx interrupt routine.

I have not yet worked with this - or similar - WiFi modems, so I can hardly claim much experience. However, starting a packet with the termination character ('\n') seems a bit like a break of protocol to me. Perhaps you could just ignore such starting terminators, i.e. drop '\n' characters for buffer index zero. If I understood your issue correctly ...