Problem to get strings with getc

[id31]

Hi all,
I'm using PIC18f8722.

I try to get a string in UART. The Uart pins is not the hw pins (PINS D2, D7).
My method is to getc(STREAM) every char to an array of chars. the program call getc only after kbhit(STREAM).
when I use the same methods for numbers (hex) it works well.
when I use fprintf() the data is going well to my PC.

Example:

[temtronic]

EVERY time you use the hardware UART you MUST add 'errors' to the uses rs232(...options...), EVERY time.
Since you didn't post your code, I will assume 'errors' is not in the list.

It is required into order for the compiler to add a bit of code to keep the UART from 'locking up' after 2-3 characters are received.

Also you should look at the ex_sisr.c example program, as ANY serial input should be done in an ISR ( Interrupt Service Routine). This allows the pIC to do a LOT more than just wait for 'something' to come in.

Jay

[id31]

Hi, thank you for the quick reply.
As i wrote before - the uart is not HW so i use kbhit() instead of int_rda.
when i configured the uart i added errors.

[temtronic]

oops... gues I need TRIfocals.....sigh,getting old ...
OK have to ask why can't you use the HW UART?

You should post your serial ISR so we can see. All ISRs must be small and fast, NO fancy math, no prints, no delays.....

Jay

[Ttelmah]

Problem is time.

Understand that 'kbhit' will only return true, once the character has already started. So using kbhit, you will be late actually starting to receive the character. Use the option 'SAMPLE_EARLY' in your #use rs232 setup. This tells the getc code to not wait half a bit time after being called.

Also understand that using software serial, you can only send or receive at any time. If data arrives while you are sending, it will be lost.

[id31]

The other UARTs is for other communication serials (I have 3 "ports").
I tried "SAMPLE EARLY" but it didn't help.
still I got the start of the string wrong and after correct.

the method is:

char a[100]={0};
run_timer4(); //I have a function that when interrupt it set timeout=TRUE
for (int i=0;i<100;i++)
{
while ((!kbhit(UART_STREAM) && (!timout))
{
a[i]=getc(UART_STREAM);
}
}

[jeremiah]

You need fgetc() for streams.

Also, understand that your timing must be very tight and you shouldn't use interrupts while receiving data. Interrupts can corrupt the data stream when doing SW uart. There is an option to DISABLE_INTS in the #use rs232() directive that is specifically for SW uarts.

[id31]

I used fgetc() - didn't change the results..
I enable "DISABLE_INTS" - still the same..

:(

[Ttelmah]

Your new logic is testing the wrong way round. You are calling the getc, when kbhit is not true:

[id31]

OK!
it solved.

first of all - thank you for the quick replies!
YOU WERE RIGHT ALL THE TIME - the problem is time.

it was my fault not to paste the exact code..
the exact code is

char a[100];
if (kbhit(UART_STREAM))
{
for (int i=0;i<100;i++)
{
a[i]=0;
}
run_timer4(); //I have a function that when interrupt it set timeout=TRUE
for (int i=0;i<100;i++)
{
while ((!kbhit(UART_STREAM) && (!timout))
{
a[i]=getc(UART_STREAM);
}
}
}
}

the bolded text (init the array) took too much time. so I init at when declared (as i wrote i did.. ) and it solved!

so - thank you and im sorry, i learned for the next time.
I have 2 more questions please:
1. I have 2MHz crystal - so why the init of the array took so much time?
2. Why did you advise me to use fgetc and not getc?

[jeremiah]

[Ttelmah]

It's also worth asking 'why'.
Just clear the array before you start waiting for the character.
Understand that with the software UART, when you see 'kbhit' you are already inside the character being received, and you have less than half a bit time to actually start reading the data.
There is actually no point in clearing the array anyway. Just write a null when you exit (last character or timeout). The rest of the array is being filled with the characters as they are received.