See the help on ComRd:
Return Value
| Name |
Type |
Description |
| BytesRead |
int |
Number of bytes read from the input queue.
If an error occurs, the return value is a negative error code. |
And:
ComRd times out when the input queue remains empty for an entire timeout period. On a timeout, ComRd returns the number of bytes actually written (typo: actually read) and sets rs232err to -99
Try something like this:
result = ComRd (Port_CAN, Reponse, 11);
if (result < 0)
// Print the value of result
// Terminate function
else if (result < 11)
// Not enough characters!
// Print how many characters received and possibly the message received
// Terminate function
else
// Interpret the string
This is the very basic of error checking: functions very ofter return a meaningful value that you must check before proceeding.
If you are not familiar with these concepts you should take some time to read and experiment a little on this. It's not that I am fussy: error checking is the basis of I/O code.
- If you receive an error, you must handle it; at least inform the user and do not proceed as if all was good!
- If you don't receive the expected result, you must handle this situation: you may need to change something in your code, or cabling, or who knows what
You cannot go on assuming all works well, because at some moment something will not. How many times your phone calls are not good? The person is not there, the line is noisy, the phone goes out of battery... the same applies here, and error checking is the way to address these situations.
