Initialization of uart interrupt in codevisionavr

#Initialization of uart interrupt in codevisionavr serial#

Open the console and hit some keyboard keys. Process main task upon timebase interruptР”В«uild the project and flash the target. Process console incoming byte upon interrupt

Try the following main() function: // Global variables Note that both console_rx_byte and console_rx_irq variables must be declared as global variables to be available both from the main() function and from the USART2_IRQHandler() function. RXNE flags automatically clears when reading RDR. If ((USART2->ISR & USART_ISR_RXNE) = USART_ISR_RXNE) * This function handles USART2 interrupts Now, write a simple interrupt handler: /* Set priority level 1 for USART2 interrupt Next enable USART2 interrupt to propagate thru NVIC controller with priority 1 (this is done in BSP_NVIC_Init() function). If there are some other important tasks to do between RXNE readings, you will likely miss quite a few incoming bytes.Р”В®dit the BSP_Console_Init() function to enable the interrupt upon RXNE event.In the above example, the CPU is fully busy reading the RXNE flag.We already discussed the drawbacks of the polling approach for the push-button: The above main() function is just polling data on the USART2 RX register. When it is set, we transfer the RDR register content into the rx_byte local variable.Р”В«uild the program, flash the target and hit some keyboard keys in the console windows: We continuously test the USART2 RXNE flag.

What this example does is pretty obvious. My_printf('You've hit the '%c' key ', rx_byte) If ( (USART2->ISR & USART_ISR_RXNE) = USART_ISR_RXNE ) If there is something in USART RDR register Terminate the debug session and edit the main() function: // Main program It is your responsibility to read incomming bytes when available, and before a new one arrives and take place in the RDR register or produces an Overrun error. USART peripheral is therefore not storing successive incoming bytes. You can permanently disable the Overrun error detection by setting the OVRDIS bit in the CR3 register.Р”Р„nyway, when you send characters one by one, you can see that RDR only store the last one being received.

You can do that from the debugger register view and make sure ORE resets. If this happens, the RX process will not work anymore until you clear EOR by writing 1 to the ORECF bit, in the ICR register. This bit is set by hardware when the data currently being received cannot be transferred into RDR because it is not empty. Moreover, the flag ORE (Overrun error) is set to 1. If you try to press 2 keys in a row on the keyboard from the terminal application, you will see that only the first one is stored in RDR register. You can continue repeating the above steps with differents keyboard keys, and verify that the last pressed key has always arrived in the RDR register. You will see that 0X62 byte has now arrived in the RDR register. Repeat the above steps, but instead of hitting the key РІР‚ВaРІР‚в„ў at step 3, hit the key РІР‚ВbРІР‚в„ў (only once). Once started, the debugger will stop at the beginning of the main() function, waiting for you to command execution.

#Initialization of uart interrupt in codevisionavr serial#

Open a serial terminal program (Putty) with the correct COM port settings.

Make the main() function as simple as this: // Main program USART2->CR1 |= USART_CR1_TE | USART_CR1_RE 8-bit, 1 start, 1 stop, CTS/RTS disabled

Clear USART2 configuration (reset state) GPIOA->MODER &= ~(GPIO_MODER_MODER2_Msk | GPIO_MODER_MODER3_Msk) Configure PA2 and PA3 as Alternate function Doing so, the PA3 pin is used as the USART2 RX alternate function. Make sure that both TX and RX mode are enabled (should be already there). In this tutorial, we want to receive incoming data from the terminal window as well.Р”В«elow is our function that initialize USART2. So far, we have been using USART2 in TX mode only, to output console messages with my_printf() function.