Email: Password: Remember Me | Create Account (Free)

Back to Subject List

Old thread has been locked -- no new posts accepted in this thread
???
02/25/05 10:54
Read: times


 
#88436 - Check
Responding to: ???'s previous message
Steve M. Taylor said:
I have seen so many people assume that the serial port MUST be working. TEST it with an oscilloscope.

Evem without a scope, loop-back tests can give you a high degree of confidence:

1. Put a loopback connector on the PC's COM port.
If this doesn't work, you obviously have a PC problem.
If this works, you know that all the PC's transmit and receive hardware & software is working, but it could still have baud-rate or framing errors, or other problems that allow it to talk to itself but nothing else.

2. Short-circuit the UART Rx and Tx pins at the microcontroller (you will need to isolate the processor's Tx pin).
Connect to the PC - characters sent by the PC should be looped back to the PC.
If this doesn't work, you have a problem with the cable, or something on your target board.
If this works, you know that all your target's transmit and receive hardware is also working up to the processor pins, but the PC could still have baud-rate or framing errors, etc, or there could be a problem in your software and/or the microcontroller.



List of 26 messages in thread
TopicAuthorDate
UART doesn't work in XP HyperTerminal?            01/01/70 00:00      
   Settings ?            01/01/70 00:00      
      It has Identical settings on XP            01/01/70 00:00      
         Turn Off handshaking            01/01/70 00:00      
            Port com does function fine            01/01/70 00:00      
               What LED?            01/01/70 00:00      
   Com port            01/01/70 00:00      
      are you?            01/01/70 00:00      
         The max232 is not needed?????            01/01/70 00:00      
            It *is* needed!            01/01/70 00:00      
      Mainboard's com is right            01/01/70 00:00      
         loopback            01/01/70 00:00      
         Check            01/01/70 00:00      
            Check            01/01/70 00:00      
               Sure            01/01/70 00:00      
                  but            01/01/70 00:00      
            I already probed the port, cable 0.5mts            01/01/70 00:00      
               Don't guess            01/01/70 00:00      
         too much confidence            01/01/70 00:00      
            Waaaaaaaaay too much confidence !!            01/01/70 00:00      
   it would be some drivers missing            01/01/70 00:00      
      Some Drivers Really Missing            01/01/70 00:00      
      XP            01/01/70 00:00      
      Do the loopback!            01/01/70 00:00      
   Try one more.            01/01/70 00:00      
      Really??            01/01/70 00:00      

Back to Subject List