UART receive interrupt issue
Posted: 09 Sep 2013 15:27
I'm communicating with an other device over UART. I'm requesting certain information by sending commands to the device. I'm repeating the command until I receive a usable answer.
The problem I have is that the ISR I use works fine when you're dealing with static and known string lengths. But in this case the strings I'm receiving could have different lengths at any time. Depending e.g. on if the device has an error or not. So lets say that the first 5 requests result in an error string which is shorter or longer than the expected length. And at attempt 6 it does result a in a string with the expected length, the (software) buffer seems corrupted some way. The bytes aren't on the right place, like some framing problem.
This is the ISR as I it is now:
And the way I handle it in the main code:
How should my code be setup to handle this situation better?
The problem I have is that the ISR I use works fine when you're dealing with static and known string lengths. But in this case the strings I'm receiving could have different lengths at any time. Depending e.g. on if the device has an error or not. So lets say that the first 5 requests result in an error string which is shorter or longer than the expected length. And at attempt 6 it does result a in a string with the expected length, the (software) buffer seems corrupted some way. The bytes aren't on the right place, like some framing problem.
This is the ISR as I it is now:
Code: Select all
void UART1RXInterrupt() iv IVT_ADDR_U1RXINTERRUPT {
uart_rd2[LoopVar0] = UART1_Read();
LoopVar0++;
if (LoopVar0 >= q) //Fill array until certain lenght
{
LoopVar0 = 0;
ready0 = 1;
}
if (U1STA.OERR = 1)
{
U1STA.OERR = 0;
U1STA.FERR = 0;
}
U1RXIF_bit = 0;
}
Code: Select all
UART1_Write_Text("A"); //Command
if (ready0 == 1)//Data received
{
if (uart_rd2[0] == 0x4F && uart_rd2[1] == 0x4B) //Check message ID
{
//Found answer that I was looking for
}
ready0 = 0;
}
else
delay_ms(2000); //Wait and try again
}