UART 4 bit numeric value communication

[soundarya_h_s]

I am doing the project to control linear motor, For that I am using UART to send start and stop command to start and stop motor, as like this i sending different rpm value from 100 to 3000 randomly to change the ramp of the motor.

The problem that i am facing is for 3 digit number RPM i am getting output, but when is comes to 4 digit value i am not getting proper putput, 
For example:

For 1000 RPM, I am getting 100 RPM as out put

• Baud Rate: 115200 bps
• Data Bits: 8
• Parity: None
• Stop Bits: 1

 

void
HAL_UART_RxCpltCallback(UART_HandleTypeDef* huart)
{
 int cmd_ok = 0;
 rxbuffer[strlen(rxbuffer)] = '\0';
 if (strncmp((const char*)rxbuffer, "start", 6) == 0)
 {
 rxbuffer[strlen(rxbuffer)] = '\0';
 flag = 1;
 cmd_ok = 1;
 // MC_StartMotor1();
 }
 else if (strncmp((const char*)rxbuffer, "stop", 5) == 0)
 {
 rxbuffer[strlen(rxbuffer)] = '\0';
 flag = 0;
 cmd_ok = 1;
 // MC_StopMotor1();
 }
 else
 {
 rxbuffer[strlen(rxbuffer)] = '\0';
 char* endptr;
 uint16_t rpmValue = strtol((char*)rxbuffer, &endptr, 10);
 // rpmValue = atoi((char*)rxbuffer);
 if (rxbuffer[0] != '\0' && *endptr == '\0' && rpmValue >= 100 && rpmValue <= 3000)
 {
 MC_ProgramSpeedRampMotor1(rpmValue, 30000);
 // HAL_Delay(60000);
 cmd_ok = 1;
 }
 }

 if (cmd_ok == 1)
 {
 memset(rxbuffer, 0, sizeof(rxbuffer));
 cmd_ok = 0;
 rxindex = 0;
 }
 else
 {
 rxindex++;
 }
 HAL_UART_Receive_IT(&huart2, ((uint8_t*)rxbuffer) + strlen(rxbuffer), 1);
}

[Andrew Neil]

Please use this button to properly post source code:

 

[soundarya_h_s]

void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{


		int cmd_ok = 0;

		rxbuffer[strlen(rxbuffer)] = '\0';

		if (strncmp((const char*)rxbuffer, "start", 6) == 0)
		{
			rxbuffer[strlen(rxbuffer)] = '\0';
			flag = 1;
			cmd_ok = 1;
			//MC_StartMotor1();

		}
		else if (strncmp((const char*)rxbuffer, "stop", 5) == 0)
		{
			rxbuffer[strlen(rxbuffer)] = '\0';
			flag = 0;
			cmd_ok = 1;
			//MC_StopMotor1();
		}
		else
		{
			rxbuffer[strlen(rxbuffer)] = '\0';
			char *endptr;
			uint16_t rpmValue = strtol((char*)rxbuffer, &endptr, 10);

			//rpmValue = atoi((char*)rxbuffer);
			if (rxbuffer[0] != '\0' && *endptr == '\0' && rpmValue >= 100 && rpmValue <= 3000)
			{
				MC_ProgramSpeedRampMotor1(rpmValue,30000);
				//HAL_Delay(60000);
				 cmd_ok = 1;
			}

		}
		if(cmd_ok == 1)
		{
			memset(rxbuffer, 0, sizeof(rxbuffer));
			cmd_ok = 0;
			rxindex = 0;
		}
		else
		{
			rxindex++;
		}

		HAL_UART_Receive_IT(&huart2, ((uint8_t *)rxbuffer) + strlen(rxbuffer), 1);

}

[Karl Yamashita]

You should use HAL_UARTEx_ReceiveToIdle_DMA since you have variable size strings. Check this git project which explains how it's used. https://github.com/karlyamashita/Nucleo-G431RB_Three_UART/wiki

 

Also you should not be doing any calculations or calls to another function within a interrupt. Save the data and set a flag. Then check the flag in the main loop and then do your calculation or calls.

[Peter BENSCH]

@soundarya_h_s For your convenience, I have prettied it up with a code beautifier and inserted it with </>.

[Andrew Neil]

A bit confused by this: Is the problem in the sending, or the receiving?

You've only shown receive code, but are you certain that the transmitting code is working properly?

Have you tried stepping the code to see what happens, character-by-character, as the command is received?

It looks like your commands are text-based, so you could test using a terminal ...

 

What is going on here:

---

@soundarya_h_s wrote:

 

 

 

 rxbuffer[strlen(rxbuffer)] = '\0';

 

---

strlen is only going to work if the rxbuffer is already NULL-terminated - so this is either pointless, or broken.

 

[soundarya_h_s]

Start and stop commands are working properly, when it comes to sending 4 digit numeric value through uart, it is taking as 3 digit number

[Andrew Neil]

---

@soundarya_h_s wrote:

 when it comes to sending 4 digit numeric value through uart, it is taking as 3 digit number

---

Still unclear whether the problem is in the sending or the receiving?

1. Have you confirmed that the commands are being sent correctly?

2. If the sending is correct, Have you tried stepping the receiving code to see what happens, character-by-character, as the command is received?

Again, It looks like your commands are text-based, so you could test using a terminal ...

---

You titled the post, "UART 4 bit (sic?) numeric value communication" - is that a typo?

Did you mean 4-digit ?

 

[TDK]

You're terminating things before the last digit comes in.

> if (rxbuffer[0] != '\0' && *endptr == '\0' && rpmValue >= 100 && rpmValue <= 3000)

Imagine that you've received 3 digits "100". Code gets to this line, it passes (since rpmValue >= 100), so you terminate things and set the speed to 100.

The proper way would be to terminate commands with a "\n" and only act upon those when the terminating character is sent.

 

[soundarya_h_s]

void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
	int cmd_ok = 0;
 static int rx_index = 0;
	if (rxbuffer[rx_index] == '\n' )
	{
		if (rx_index > 0 && rxbuffer[rx_index - 1] == '\r')
		{
			rxbuffer[rx_index] = '\0';
			rxbuffer[rx_index - 1] = '\0';
			rx_index = 0;
			int j = 0;
			while (rxbuffer[j] != '\0' && rxbuffer[j] == "stop"[j])
			{
				j++;
			}
			if (j == 4 && rxbuffer[j] == '\0')
			{
				stopflag = 1;
				cmd_ok = 1;
				//MC_StartMotor1();
			}
			else if(j == 2)
			{
				int i = 0;
				while (rxbuffer[i] != '\0' && rxbuffer[i] == "start"[i])
				{
					i++;
				}
				if (i == 5 && rxbuffer[i] == '\0')
				{
					startflag = 1;
					cmd_ok = 1;
					//MC_StopMotor1();
				}
			}
			else
			{
				uint16_t rpmValue = atoi((char*)rxbuffer);
				 for (int i = 0; rxbuffer[i] != '\0'; i++)
				{
					if (!isdigit(rxbuffer[i]))
					{
						rxbuffer[i] = '\0';
						break;
					}
				}
				if (100 <= rpmValue && rpmValue <= 3000)
				{
					 MC_ProgramSpeedRampMotor1(rpmValue,60000);
					 cmd_ok = 1;
				}
				else
				{
					 txflag = 1;
					 cmd_ok =1;
				}
			}
		 }
	 }

[Andrew Neil]

Have you tested that code?

You still have problems if rxbuffer is uint16_t; eg,

uint16_t rpmValue = atoi((char*)rxbuffer);