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Serial communication problem upon soldering

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cimulation

New Member
I am trying to make a circuitboard for my circuit which is prototyped on the breadboard.

There are serial port Tx and Rx pins from a PIC16f688 which i use to interface to the PC. On the breadboard these work fine, when i soldered these onto my board the trasmission has a lot of errors. I have checked the connections and I am using wires to solder these onto the board.

Is there a recommended way of soldering when a serial transmission is concernced. What can be done to prevent these errors.

Best Regards and TIA.
Sumit
 

AtomSoft

Well-Known Member
it has nothing to do with the soldering, unless its not right like the solder isnt making contact well or there is too much flux or you crossed traces or may a wire is melted somewhere and touching something eles
 

be80be

Well-Known Member
I am trying to make a circuitboard for my circuit which is prototyped on the breadboard.

There are serial port Tx and Rx pins from a PIC16f688 which i use to interface to the PC. On the breadboard these work fine, when i soldered these onto my board the trasmission has a lot of errors. I have checked the connections and I am using wires to solder these onto the board.

Is there a recommended way of soldering when a serial transmission is concernced. What can be done to prevent these errors.
So it works on the solderless bread board with out a max 232 right?
If it did then it was the capacitance of the board would be the only thing that could of changed if you made the circuit the same. But you need a level converter a max232 would be the easy way to go.
 

BeeBop

Active Member
If you wired a PC serial port Tx to the PICs Rx without a level converter you may have fried your PIC. + or - ~10 volts on a pic pin :eek: Check the data sheet!

You haven't stated that you are using a level converter, and the diagram does not show one.
 

be80be

Well-Known Member
If he has a newer computer the voltage level may be lower some newer ones use the same
power that the usb uses. But I was thinking the same thing He may have cooked it.
 

geko

Active Member
The output from the PICs UART is postive logic, i.e. 1==high, 0==low.

RS232 uses negative logic where a 1 is low and a 0 is high so even if the voltage levels were being detected as high and low, the data itself would be inverted including the stop and start bits.

We are of course making the assumption it's connected to an RS232 serial port. The O/P hasn't explicitly stated that is the case, only that it's connected to a PC.
 

Mr RB

Well-Known Member
PC RS232 ports have a fairly high output impedance, typically about 330 ohms. They will tolerate indefinite short circuits.

Connected direct to a PIC pin it would have pushed the PIC internal port diodes to about 30mA, not recommended of course but it's very unlikely to have blown the PIC.
 
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