Recording the data recieved from UART

[Alex_2221]

Hello everyone, in my project, I'm sending temperature via UART and want to recieve a 2 digit number and record it in a variable. I'm able to read data and echo it back, but as far as I understood I need to recieve a two bytes of data and I'm receiving only one byte everytime UART interrupt works. Plus I wanted to see the content of the variable, in which I save the data and it's only the left most digit of the number I'm sending and the ASCII equivalent of it. For example, If I send 15, my debugger shows me something like (49' 1) and as you may know 49 is the ASCII form of 1 and when I run my code I can recieve back my right most digit in ASCII for example, for 15 I get 53 which is the ASCII form of 5. I also try to send back the data together with the temperature by UART_Send function, and in this case I only can see the ASCII form of the right most digit. So, I'm now able to only recieve the right most digit of the numbers I send and they're in ASCII what can I do to save both digits in decimal in a variable?

In order that you better understand what I'm saying, I added the screenshot of my debugger, my serial port terminal, and my main.c file, so that you can see my code.

Your help will be greatly appreciated,

Sincerely, 

Alex

[xiangjun_rong]

Hi,

For usart module, it can transmit or receive only ONE byte, pls refer to the usart data registers:

So the Usart will trigger interrupt after it has received/transmitted a Byte.

I see that your data is half word(16 bits), I think you can transfer the half word(temperature variable) with two byte.

uint16_t temperature;

char byte_L, byte_H;

void halfWord(uint16_t var)

{

byte_L=(char)(var&0xFF);

byte_H=(char)((var>>8)&0xFF);

UART_SendByte(LPC_UART3,byte_L);

UART_SendByte(LPC_UART3,byte_H);

UART_SendByte(LPC_UART3,0xFF);

UART_SendByte(LPC_UART3,0xFF);

}

I suggest you delete the line  uint8_t len=sprintf((char*)buffStr,"Hello.Temp is %u\n %u\n",temp, data1);

You can transfer data directly. The 0xFFFF is a separator or mark so that the receiver know which is high byte which is low byte.

Hope it can help you

BR

XiangJun Rong

[Alex_2221]

• @xiangjun_rong Thank you very much for your time and your reply. However, I can send the temperature, which is 2 bytes fine. My problem is I cannot save the data I enter via serial port using uart_receivebyte in the interrupt! How can I save the data which is 2 bytes ( 2 digit number string)?

[Alex_2221]

@xiangjun_rong Thank you very much for your time and your reply. However, I can send the temperature, which is 2 bytes fine. My problem is I cannot save the data I enter via serial port using uart_receivebytr in the interrupt! How can I save the data which is 2 bytes ( 2 digit number string)?

[xiangjun_rong · Accepted solution]

Hi,

Regarding your following code, I think you can define an array.

//global variable

#define N 100

char array[N];

uint32_t index=0;

void UART_IntReceive(void)
{

data[index]=UART_ReceiveByte(LPC_UART3);

index++;

if (index>==N) index=0;
//I do not suggest you call UART_SendByte() in the receiver ISR
//UART_SendByte(LPC_UART3,data);

}

Is it what you expected?

BR

XiangJun Rong

[Alex_2221]

@xiangjun_rong Thanks a lot, man. It worked

[Alex_2221]

Yeah absolutely, it's what I expected and I think it makes sense. Thank you so much, I'll give it a try.  

[Alex_2221]

@xiangjun_rong Your replies always helped me. I always value your opinion.