So... I've made the jump to an STM32G081 (on an eval card). The advice I received was correct -- while similar, there are enough differences to make the software significantly different. I have successfully set up my clock tree and blinked some LEDs (at expected rates - hence why I think the clocks are correct). I believe the UART clock is 64MHz. I am dividing it by 8 (I think) to get 8MHz for my usart_ker_ckpres. I am now [again] trying to get USART tx to work. I am able to successfully transmit one character. However, I am not receiving anything after that. II think it has to be something with how I am checking "tx done" flags, but I can't spot it. Any advice would be much appreciated.
Configuration:
/**
* @brief UART3 GPIO Configuration (Tx: PC10, Rx: PC11)
*/
void uart_UART3_GPIO_config(void)
{
//PC10-Tx, PC11-Rx
//Enable PortC Clock
RCC->IOPENR |= RCC_IOPENR_GPIOCEN;
//Mode to AF (UART3)
GPIOC->MODER &= ~(GPIO_MODER_MODE10 | GPIO_MODER_MODE11);
GPIOC->MODER |= (GPIO_MODER_MODE11_1 | GPIO_MODER_MODE10_1);
//Set Output(Tx) to push-pull
GPIOC->OTYPER &= ~GPIO_OTYPER_OT10;
//Set output to "high speed"
GPIOC->OSPEEDR &= ~GPIO_OSPEEDR_OSPEED10;
GPIOC->OSPEEDR |= GPIO_OSPEEDR_OSPEED10_1;
//Disable pullups on input
GPIOC->PUPDR &= ~GPIO_PUPDR_PUPD11;
//Map alternate functions (see DS12232, p. 50)
//PC10 --> AF0 = USART3_TX, PC11 --> AF0 = USART3_RX
GPIOC->AFR[1] &= ~(GPIO_AFRH_AFSEL10 | GPIO_AFRH_AFSEL11);
}
/**
* @brief UART3 Peripheral Configuration
*/
void uart_UART3_config(void)
{
//115200, 8N1
//Enable USART3 clock
RCC->APBENR1 |= RCC_APBENR1_USART3EN;
//Set DW length, oversample by 16, parity ctrl disabled, parity even
USART3->CR1 &= ~(USART_CR1_M1 | USART_CR1_M0 | USART_CR1_OVER8 | USART_CR1_PCE | USART_CR1_PS);
//Enable Transmit
USART3->CR1 |= USART_CR1_TE;
//One stop bit
USART3->CR2 &= ~USART_CR2_STOP;
//Disable hardware flow control
USART3->CR3 &= ~(USART_CR3_CTSE | USART_CR3_RTSE);
//Set Prescaler to 64/8 = 8MHz
USART3->PRESC &= ~USART_PRESC_PRESCALER;
USART3->PRESC |= USART_PRESC_PRESCALER_2;
//Set baud rate to 115200 = Fclk/(16*USARTDIV)
// USARTDIV = Fclk/BR = 8MHz/115200 = 69.4444
// 69 = 0x45
// 0.44 --> 0.4444*16 = 7.1104 => 7
//USART3->BRR |= ((0x45UL << 4) | (0x7UL << 0));
// USART3->BRR = 0x341; //Baud: 9600
USART3->BRR = 0x046; //Baud: 115200
//Clear unnecessary flags/enables
USART3->CR2 &= ~(USART_CR2_LINEN | USART_CR2_CLKEN);
USART3->CR3 &= ~(USART_CR3_SCEN | USART_CR3_HDSEL | USART_CR3_IREN);
//Enable USART
USART3->CR1 |= USART_CR1_UE;
}
Transmit:
/**
* @brief UART3 Transmit Function
*/
bool uart_UART3_transmit(uint8_t *data, uint8_t len, uint32_t timeout)
{
//Wait on TXE to start transmit
//Write to DR as TXE flag is HIGH (Tx buffer Empty)
uint8_t dataIdx = 0;
uint32_t startTick = rcc_msGetTicks();
while(dataIdx < len)
{
if(USART3->ISR & USART_ISR_TXE_TXFNF) //Tx buffer empty
{
USART3->TDR = data[dataIdx];
dataIdx++;
}
else { //Manage timeout
if((rcc_msGetTicks() - startTick) >= timeout)
{
gpio_LED_writeRed(LED_ON);
return(false);
}
}
}
//Wait for done flag
while(USART3->ISR & USART_ISR_TCBGT)
{
if((rcc_msGetTicks() - startTick) >= timeout)
{
gpio_LED_writeOrange(LED_ON);
return(false);
}
}
return(true);
}
Usage:
int main(void)
{
uint8_t txChar[] = "JELLO";
cfgPwr(); //Needs to happen first to allow higher clock speeds
rcc_HSE_config();
rcc_SysTick_config(64000); //Clock is 64MHz, want 1ms tick (1kHz)
uart_UART3_GPIO_config();
uart_UART3_config();
gpio_LED_config();
while(1)
{
gpio_LED_toggleGreen();
rcc_msDelay(250);
// gpio_LED_toggleOrange();
rcc_msDelay(250);
// gpio_LED_toggleRed();
rcc_msDelay(250);
gpio_LED_toggleBlue();
rcc_msDelay(250);
// printf("Hello world!\r\n");
uart_UART3_transmit(txChar, 5, 100);
}
}
Is there something seriously wrong with my uart_UART3_transmit function or am I missing a critical bit in my configuration function?
P.S. I am [somewhat] confident in my BRR setting (I know it's hard coded right now...), because when I change the first letter, I receive the right character. In the "usage" example above, I see J (0x4A). If I change txChar to be "HELLO", I see H (0x48) in my terminal window.
