I'm using STM32F407G-DISC1 board, SYS_TICK handler is not getting called after enabling flags in SysTick Control and Status Register which is at 0xE000E010 memory mapped location. SysTick Reload Value Register value is set to 15999.
void init_systick_timer(uint32_t tick_hz)
{
uint32_t *pSRVR = (uint32_t*)0xE000E014;
uint32_t *pSCSR = (uint32_t*)0xE000E010;
/* calculation of reload value */
uint32_t count_value = (SYSTICK_TIM_CLK/tick_hz)-1;
//Clear the value of SVR
*pSRVR &= ~(0x00FFFFFFFF);
//load the value in to SVR
*pSRVR |= count_value;
//do some settings
*pSCSR |= ( 1 << 1); //Enables SysTick exception request:
*pSCSR |= ( 1 << 2); //Indicates the clock source, processor clock source
//enable the systick
*pSCSR |= ( 1 << 0); //enables the counter
}
void SysTick_Handler(void)
{
}
I would rather recomment to do not reinvent the wheel and use standard STM provided CMSIS headers.
Your way of defining the registers is incorrect. It will not work correctly if decide to read theis values back. Compiler will simple optimize the reads from the memory out. They have to be volatile.
But abstracting from that you need to enable the interrupt in the NVIC controller. Without that the systick timer will only set the pending flag without invoking the handler.
Related
I have an ATTiny that is supposed to receive commands over UART. I have a simple display of eight LEDs that should show the contents of the most recent byte received. I am using an interrupt to read data as it is received. No matter what data I send UDR always reads 0xFF in the interrupt. I know the interrupt is being triggered since the display changes from 0x00 to 0xFF, but it never displays the value I sent over the serial bus.
This is how I enable UART.
UBRRH = UBRRH_VALUE;
UBRRL = UBRRL_VALUE;
#if USE_2X
UCSRA |= (1U << U2X);
#else
UCSRA &= ~(1U << U2X);
#endif
// Enable receiver and interrupt
UCSRB = (1U << RXEN) | (1U << RXCIE);
// No parity, 8 Data Bits, 1 Stop Bit
UCSRC = (1U << UCSZ1) | (1U << UCSZ0);
This is the code in the interrupt. I have tested display() and it functions correctly on its own thus implying message is always 0xFF.
ISR(USART_RXC_vect) {
uint8_t message = UDR;
display(message);
}
I am confident that my computer is sending the correct information, but I have only tested it with a pseudo-terminal to print out the sent bytes. I intend to snoop the hardware connection with an oscilloscope, but I don't believe that is the issue. Is there something that is causing UDR to always read as 0xFF?
Edit:
I have snooped the connection with an oscilloscope and have verified that the computer is sending the correct data, at the correct rate. However, the ATTiny is not operating at the correct baud rate. At 2400 baud pulses should be about 400 microseconds long, however the microcontroller is producing pulses over 3 milliseconds long. This explains why it would always read 0xFF, the computer would send nearly the entire byte when the controller thought it was receiving the start bit, when the controller tried to read the remaining data the lines would be undriven, resulting in it reading all ones. I still don't know why this is the case as I believe I am properly setting the baud rate on the controller.
Edit:
The issue has been resolved. By default the clock prescaler is set to 8, so the device was only operating at 1MHz, not 8MHz. Setting the clock prescaler to 1 solved the problem.
There can be several problems with uart communication. First check some things:
Is controller configured with the right clock?
Internal/External
Is F_CPU defined for <util/setbaud.h>?
Is BAUD defined for <util/setbaud.h>?
Are you using a controller like ATmega16 that has special register access?
If you are using an external clock (that should not be devided) is CKDIV8 disabled in FUSES or in special registers at some controllers?
Is:
Baudrate,
Paritybit,
Stopbit
setup corret on Transmitter and Receiver
Debug:
If you are using a PC for communication, create a loopback at the UART adapter and check with a terminal (TeraTerm, Putty, ...) if the messages you send are received correctly.
You also can enable the TX controller and check if loopback is working on your uC.
If it is possible try to write the received data to some leds to check if some date is received
Is GND betweend receiver and transmitter connected?
Are the voltage levels between transmitter and receiver the same?
Do transmitter and receiver have its own source? (Then do not connect VCC!)
Check if the clock on the controller is correct (switch on an led with _delay_ms() function every second)
Example Program
#define F_CPU 12000000UL
#define BAUD 9600UL
#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/setbaud.h>
ISR(USART_RXC_vect)
{
volatile unsigned char message = UDR;
// If it is possible try to write the received data to
// LEDs (if there are some at your board)
display(message);
}
int main()
{
// To allow changes to clock prescaler it is necessary to set the
// CCP register (Datasheet page 23)!
CCP = 0xD8;
// RESET the clock prescaler from /8 to /1 !!!!
// Or it is necessary to divide F_CPU through the CLK_PRESCALER
CLKPSR = 0x00;
UBRRH = UBRRH_VALUE;
UBRRL = UBRRL_VALUE;
#if USE_2X
UCSRA |= (1<<U2X);
#else
UCSRA &= ~(1<<U2X);
#endif
// Enable receiver and interrupt
UCSRB = (1U << RXEN) | (1U << RXCIE);
// No parity, 8 Data Bits, 1 Stop Bit
// Not necessary! Mostly ATmega controller
// have 8 bit mode initialized at startup
//UCSRC = (1U << UCSZ1) | (1U << UCSZ0);
// If you are using ATmega8/16 it is necessary to do some
// special things to write to the UBRRH and UCSRC register!
// See ATmega16 datasheet at page 162
// Do not forget to enable interrupts globally!
sei();
while(1);
}
Please explain what the display() function is doing...
I'm working on an stm32l467 and trying to run an ISR when i push the user-push-button. Everything looks to be setup correctly. I have looked at the registers in the debugger (Keil uV) and everything looks good, but when i push the button I end up in the default handler and can't understand why the handler is not running.
Running in the debugger i can see that when i push the button, i get an interrupt-pending (EXTI->PR1) flag, but the code then jumps to the the default handler. I can't see what i'm missing. I know there are easier ways to setup interrupts using the HAL layer, i'm just trying to understand what registers must be accessed from a low-level.
Can anyone suggest a missing step to this?
#include <stm32l4xx.h>
#define DELAY 1
void delay1Hz(void);
bool buttonInterrupt = false;
int main(void)
{
__disable_irq();
/* Configure the clocks */
RCC->CR &= 0xFFFFFF07; //Clear ~MSIRANGE bits and MSIRGSEL bit
RCC->CR |= 0x00000088; //Set MSI to 16MHz and MSIRGSEL bit
RCC->AHB2ENR |= 0x00000001; //Enable PA5 clocks
/* Enable PA0 for output */
GPIOA->MODER &= 0xFFFFF3FF; //Clear GPIOA[5] MODER bits
GPIOA->MODER |= 0x00000400; //Enable GPIOA[5] for output
RCC->AHB2ENR |= 0x4; //ENABLE GPIOC port clk
GPIOC->MODER &= 0xF3FFFFFF; //Clear GPIOC[13] for input mode
RCC->APB2ENR |= 1; //Enable SYSCFG clk
SYSCFG->EXTICR[3] &= ~0x00F0; //CLEAR_BIT the EXTI[13] bits
SYSCFG->EXTICR[3] |= 0x20; //Enable GPIOC for EXTI[13]
EXTI->IMR1 |= 0x2000; //Unmask EXTI13
EXTI->FTSR1 |= 0x2000; //Enable falling edge trigger on pb
NVIC_EnableIRQ(EXTI15_10_IRQn); //Enable EXTI15-to-10 interrupts
__enable_irq();
for (;;)
{
if(buttonInterrupt == true) {
//flash LED's (doesn't get here)
}
}
}
void initTim2() {
//timer 2 code - not causing a problem
}
void delay1Hz() {
//delay code - not interrupt controlled
}
/* This doesn't run */
void EXTI15_10_IRQHandler(void) {
buttonInterrupt = true;
EXTI->PR1 = 0x2000;
}
Never mind: There seems to be some problem with a delay i have with timer-2. It's not using interrupts, so i'm surprised it's causing trouble. But if i take it out and use a different delay, the interrupt from the above code works fine. It's an odd one.
I've bought an STM32F411 nucleo board and now I'm trying to understand various bits and pieces of the HAL. Starting with external interrupts seemed to be a good idea, because the board has a push button which is connected to PC13. So I've set up a simple toggle-the-frequency blinky. The code below is a bit simplified:
#define LED_PIN GPIO_PIN_5
#define BTN_PIN GPIO_PIN_13
static uint32_t blink_period = 250;
int main(void)
{
HAL_Init();
SystemClock_Config();
__GPIOA_CLK_ENABLE();
GPIO_InitTypeDef pinConfig;
pinConfig.Pin = (LED_PIN);
pinConfig.Pull = GPIO_NOPULL;
pinConfig.Mode = GPIO_MODE_OUTPUT_PP;
pinConfig.Speed = GPIO_SPEED_FAST;
HAL_GPIO_Init(GPIOA, &pinConfig);
__GPIOC_CLK_ENABLE();
pinConfig.Pin = (BTN_PIN);
pinConfig.Pull = GPIO_NOPULL;
pinConfig.Mode = GPIO_MODE_IT_FALLING;
pinConfig.Speed = GPIO_SPEED_LOW;
HAL_GPIO_Init(GPIOC, &pinConfig);
HAL_NVIC_SetPriority(EXTI15_10_IRQn, 0x0F, 0x00);
HAL_NVIC_EnableIRQ(EXTI15_10_IRQn);
while (1)
{
HAL_GPIO_TogglePin(GPIOA, LED_PIN);
HAL_Delay(blink_period);
}
}
void EXTI15_10_IRQHandler(void)
{
HAL_GPIO_EXTI_IRQHandler(BTN_PIN);
}
void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin)
{
if(GPIO_Pin == BTN_PIN)
{
if (blink_period == 500)
{
blink_period = 250;
}
else
{
blink_period = 500;
}
}
}
When I push the button, an interrupt is generated and the blinky frequency changes from 1 to 2 Hz (or vice-versa). This works as intended, but why? I forgot to clear the pending interrupt flag, so the ISR should be called over and over. The datasheet clearly states that
When the selected edge occurs on the external interrupt line, an interrupt request is generated. The pending bit corresponding to the interrupt line is also set. This request is
reset by writing a ‘1’ in the pending register.
Reading a bit further reveals that this is a bit different for events:
When the selected edge occurs on the event line, an event pulse is generated. The pending bit corresponding to the event line is not set.
However, I'm not setting the button pin mode to any of the GPIO_MODE_EVT_... modes so I'm not using the event mechanism (to be honest I don't yet know what that even is - I just think that I'm not using it. Any hints are welcome).
So somewhere I should have to call void HAL_NVIC_ClearPendingIRQ (IRQn_Type IRQn), shouldn't I? It seems that clearing the flag by software is not necessary, because the ISR is not called more than once per falling edge. I've added a breakpoint in HAL_GPIO_EXTI_Callback to verify this.
Edit
As mentioned in the comments, the flag clearing code is in ST's implementation of the GPIO interrupt handler:
void HAL_GPIO_EXTI_IRQHandler(uint16_t GPIO_Pin)
{
/* EXTI line interrupt detected */
if(__HAL_GPIO_EXTI_GET_IT(GPIO_Pin) != RESET)
{
__HAL_GPIO_EXTI_CLEAR_IT(GPIO_Pin);
HAL_GPIO_EXTI_Callback(GPIO_Pin);
}
}
This handler needs to be called by the actual ISR (which is done in my code) and it clears the pending flag corresponding to the GPIO_Pin argument. So I have to write an ISR which sorts out which flags are set, and call HAL_GPIO_EXTI_IRQHandler for each, which in turn calls my HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin), again with the pin as an argument. For each external interrupt, the pin number would get checked some ~3 times (in the ISR, in the handler and in the callback)!
If that is the solution, I want my problem back.
You don't have to call HAL_NVIC_ClearPendingIRQ (IRQn_Type IRQn) because the pending bit in the NVIC will be cleared automatically upon entering HAL_GPIO_EXTI_IRQHandler.
The HAL_GPIO_EXTI_IRQHandler() implementation clears the pending bit in the peripheral, not in the NVIC. If it didn't clear the pending bit by calling __HAL_GPIO_EXTI_CLEAR_IT(GPIO_Pin), then the handler would be called again and again. The point is that you must distinguish between the interrupt pending bit in the peripheral and the pending bit in the NVIC.
I'm trying to set up an external interrupt on my LPC812 uC. I've made the following code
#include "LPC8xx.h"
#define RLED 7 // red LED
bool pause = false;
void PININT0_IRQHandler(void)
{
pause = !pause;
}
int main(void) {
LPC_GPIO_PORT->DIR0 |= 1<<RLED; // set pin as output
LPC_GPIO_PORT->SET0 = 1<<RLED;
NVIC_EnableIRQ(PININT0_IRQn);
while (1)
{
if(!pause)
{
LPC_GPIO_PORT->CLR0 = 1<<RLED;
}
}
}
But it isn't working. Am I missing something?
I'm not familiar with NXP MCUs.
But at least place break piont inside PININT0_IRQHandler, to understand clearly that interrupt is not generated.
Also it will be nice to clear interrupt flag inside handler.
Some peripherals need interrupt permission in peripheral registers in addition to NVIC setup.
Did you setup input pin somewhere?
Your code only initialize GPIO 7 pin as output.
When I press PF8 button, I want the blackfin goes into a ISR and the counter increases 1.
I should clear or set a bit which indicates the processor has entered the ISR, but I don't know how to clear it.
My processor is BF533.
Here is my code:
// prototype
EX_INTERRUPT_HANDLER(FlagA_ISR);
volatile int count = 0;
void main(void)
{
// Register FlagA ISR to interrupt vector group 12
register_handler(ik_ivg12, FlagA_ISR);
// set direction of programmable flag PF8 to input
*pFIO_DIR &= ~PF8;
ssync();
// interrupt enable PF8
*pFIO_INEN |= PF8;
ssync();
// give interrupt when FIO_FLAG_D PF8 changes
*pFIO_MASKA_D |= PF8;
ssync();
// Bind FlagA interrupt to IVG12
*pSIC_IAR2 |= 0x00005000; // flag A IVG12
ssync();
// Enable PFA in system interrupt mask register
*pSIC_IMASK = 0x00080000;
ssync();
// enable IVG12 in core interrupt mask register
*pIMASK |= 0x00001000;
ssync();
// wait for interrupt
while(count < 5);
printf("5 interrupts received");
}
EX_INTERRUPT_HANDLER(FlagA_ISR)
{
count++;
// Needed to clear or set a bit to indicate that the processor has entered the ISR
}
I have just figured out how to solve this question.
The PFx are connected to the FIO_FLAG. We can clear our interrupt status by clearing FIO_FLAG.
Here is the code:
*pFIO_FLAG_D &= ~PF8;
ssync();
//or, you can try:
*pFIO_FLAG_C |= PF8;
ssync();