Why the maximum value of Tim4Encoder is 127 rather than 32767?

[SYoun.1]

int16_t GetTim4Encoder(){
 Tim4Encoder = __HAL_TIM_GET_COUNTER(&htim4);
 //__HAL_TIM_SET_COUNTER(&htim4,0);
 return Tim4Encoder;
}

[waclawek.jan]

What's the value of other TIM4 registers, mainly TIM4_ARR?

JW

[SYoun.1]

Thank you for answering the question. I am a beginner of STM32 so I know little about the registers. This is SerialPrint() function.

void SerialPrint(uint32_t Tx){
	if(Tx == 0){
		TxMessages[0] = '0';
		HAL_UART_Transmit(&huart1 ,(uint8_t*)&TxMessages, 1, 0xFFFF);
	}
	else{
		tmp = abs(Tx);
		j = 0;
		length = 0;
		while(tmp != 0){
			TxMessagesTmp[j++] = tmp%10 + '0';
			tmp /= 10;
			length++;
		}
		if(Tx > 0){
			for(j = 0;j < length;j++){
				TxMessages[j] = TxMessagesTmp[length-j-1];
			}
			HAL_UART_Transmit(&huart1 ,(uint8_t*)&TxMessages, length, 0xFFFF);
		}
		else if(Tx < 0){
			TxMessages[0] = '-';
			for(j = 1;j < length + 1;j++){
				TxMessages[j] = TxMessagesTmp[length-j];
			}
			HAL_UART_Transmit(&huart1 ,(uint8_t*)&TxMessages, length + 1, 0xFFFF);
		}
	}
	HAL_UART_Transmit(&huart1 ,(uint8_t*)&Apart, 1, 0xFFFF); //sizeof(TxMessages) has a problem
}

And this is main()

while (1)
 {
 /* USER CODE END WHILE */
 
 /* USER CODE BEGIN 3 */
	 SerialPrint(TIM4->ARR);
 HAL_UART_Transmit(&huart1 ,(uint8_t*)&Apart1, 2, 0xFFFF);
	 HAL_Delay(500);
 }

The value of ARR is pretty strange.

[waclawek.jan]

hummm

Maybe try some other means of printout, or simplify your program to do nothing else just print TIM4->ARR?

Or, perhaps you may try to set up some in-circuit debugging, to observe the registers more directly.

JW

[SYoun.1]

OK, I will try it. I am just confused about the relationship between this issue and ARR. In other word, after I can observe the registers, how can I solve the problem?

[turboscrew]

The counter counts from zero to ARR and then wraps back to zero. If you turn the decoder in other direction, if first wraps to ARR and then goes to zero.

When you use integers, you just interpret the value such that it's -ARR/2 to ARR/2. It's easy, if your counter is 16-bit and you use int16 as the data type. It automatically matches. That's the beauty of 2's complement. If your ARR is 0x7F, the counter increments to 0x7F (127) and then goes to zero.

[turboscrew]

Yep. Note, that you can't have negative number to print: SerialPrint(uint32_t Tx). Uint can't be negative.

And you might want to send 0x0D, 0x0A (='\r', '\n' = return, line feed) instead of the underscores?

(I guess the 'Apart' contains underscores.)

Maybe even print some string before the entity to tell what is what?

HAL_UART_Transmit(&huart1 ,(uint8_t*)"\r\nARR: ", 7, 0xFFFF);

SerialPrint(TIM4->ARR);

HAL_UART_Transmit(&huart1 ,(uint8_t*)"\r\n", 2, 0xFFFF);

[SYoun.1]

Apart is '_' to separate data from each send. SerialPrint(...) used to be SerialPrint(uint16_t Tx) but I changed to uint32 to print the ARR.

[turboscrew]

To have negative values, it should be int16 or int32.

[turboscrew]

You could also initialize the ARR to 65535 and see if that makes the difference.

If you are using CubeMX, do it there.

[SYoun.1]

Thank you, I will try it.

[turboscrew]

That's 'counter period'-field in CubeMX.