Posted on September 01, 2016 at 15:55
I'm trying to implement an asynchronous USART using ISR to communicate with FTDI and Bluetooth Modules (RX and TX at 115kbps). I have a STM32F446RE with the following test code:
void
USART6_IRQHandler(
void
)
{
if
(__HAL_USART_GET_FLAG(&stdio_handle, USART_FLAG_RXNE))
{
grb_write(&rb_rx, USART6->DR);
__HAL_USART_CLEAR_FLAG(&usart_handle, USART_FLAG_RXNE);
}
if
(__HAL_USART_GET_FLAG(&usart_handle, USART_FLAG_TXE))
{
if
(grb_is_empty(&rb_tx))
{
CLEAR_BIT(USART6->CR1, USART_CR1_TXEIE);
asm
volatile
(
''nop''
);
asm
volatile
(
''nop''
);
}
else
{
uint8_t rx;
grb_read(&rb_tx, &rx);
USART6->DR = rx;
}
}
NVIC_ClearPendingIRQ(USART6_IRQn);
}
int
main()
{
HAL_Init();
SystemInit();
SystemClock_Config();
SystemCoreClockUpdate();
__HAL_RCC_GPIOC_CLK_ENABLE();
__HAL_RCC_USART6_CLK_ENABLE();
/// Init STDIO USART
GPIO_InitTypeDef usart_gpio;
/// TX pin (C6)
usart_gpio.Pin = GPIO_PIN_6;
usart_gpio.Mode = GPIO_MODE_AF_PP;
usart_gpio.Pull = GPIO_NOPULL;
usart_gpio.Speed = GPIO_SPEED_FREQ_HIGH;
usart_gpio.Alternate = GPIO_AF8_USART6;
HAL_GPIO_Init(GPIOC, &usart_gpio);
// RX pin (C7)
usart_gpio.Pin = GPIO_PIN_7;
usart_gpio.Mode = GPIO_MODE_AF_PP;
usart_gpio.Pull = GPIO_NOPULL;
usart_gpio.Speed = GPIO_SPEED_FREQ_HIGH;
usart_gpio.Alternate = GPIO_AF8_USART6;
HAL_GPIO_Init(GPIOC, &usart_gpio);
usart_handle.Instance = USART6;
usart_handle.Init.Mode = USART_MODE_TX_RX;
usart_handle.Init.BaudRate = 9600;
usart_handle.Init.WordLength = USART_WORDLENGTH_8B;
usart_handle.Init.StopBits = USART_STOPBITS_1;
usart_handle.Init.Parity = USART_PARITY_NONE;
usart_handle.Init.CLKLastBit = USART_LASTBIT_DISABLE;
usart_handle.Init.CLKPhase = USART_PHASE_1EDGE;
usart_handle.Init.CLKPolarity = USART_POLARITY_HIGH;
assert
(HAL_USART_DeInit(usart_handle) == HAL_OK);
assert
(HAL_USART_Init(usart_handle) == HAL_OK);
__HAL_USART_ENABLE_IT(usart_handle, USART_IT_RXNE);
HAL_NVIC_ClearPendingIRQ(USART6_IRQn);
HAL_NVIC_SetPriority(USART6_IRQn, 3, 0);
HAL_NVIC_EnableIRQ(USART6_IRQn);
while
(1);
}
If I connect USART6 to an FTDI and use a terminal to send characters I can see the messages flowing in the RX line with an oscilloscope but ISR is never called. If I change the code to transmit using ISR (enable TXE interrupt and putting data in my grb) everything is transmited and visible in the PC terminal.
I tried with a sync version. Inestad of IRQ Handler I have this code:
uint16_t Data =
'a'
;
while
(1)
{
while
(!__HAL_USART_GET_FLAG(&stdio_handle, USART_FLAG_TXE));
// Wait for Empty
USART6->DR = Data;
while
(!__HAL_USART_GET_FLAG(&stdio_handle, USART_FLAG_RXNE));
// Wait for Empty
Data = USART6->DR;
// Collect Char
}
I tried to make an implementation of a loopback UART. I'm using PUTTY for this test and if I keep pressing the same key in the terminal I see some random characters appearing as a response.
Am I doing something wrong? I know that a similar code works for UART, but there is none free in this project.
