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capturing response from external device with uart

 
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KL



Joined: 24 Feb 2004
Posts: 11

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capturing response from external device with uart
PostPosted: Mon Dec 10, 2007 4:00 pm     Reply with quote

I have an external device that I send a command via the uart and need to capture its response. I initially used hyperterminal to communicate with the device and view the response.

Now I need to do this with a PIC18F452. Here is a segment of the code that does not capture the response.

char response[100];
int i;


// send my command and wait on the response with the following code:

while(kbhit())
delay_us(5);
while(i < 256)
response[ i++] = getc();


CLEAR_DISP;
LCD_position (FIRST_LINE);
for(i = 0; i <200; i++)
printf(LCD_char,"%c", response[i]);


Could someone explain what is wrong with this code or if there is a better way to accomplish the task of capturing a long response of characters.

Thank you,
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Mon Dec 10, 2007 5:16 pm     Reply with quote

There are several things wrong with it.

One major problem is that your array is only 100 bytes, but then
your loops expect the array to be 200 or 256 bytes long. That's
not going to work. If you write past the end of your array, you
will destroy the contents of other variables that are allocated in
those memory locations.

I suggest that you use the get_string() function to get the input.
It allows you to set the maximum number of characters that
you are willing to accept. This means you prevent your code
from writing past the end of your input array. The get_string()
function is in the Input.c file, which is in this directory:
Quote:
c:\Program Files\picc\Drivers\Input.c
Guest








PostPosted: Tue Dec 11, 2007 2:49 pm     Reply with quote

Thank you for the feedback. I will look at input.c.
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