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Pin Out problems


we have a problem with our own boards using the USBIzi 144.
Some standard outputs are not working correctly. They cannot be enabled (3,3V) or disabled (0V) by code. They always output approx 2,3V. The output pins were connected to the base of a NPN transistor by a 4,7k ohm resistor. After disconnecting the track to the transisitor and resistor we still measure 2,3V on the output pin no matter how it is set (high or low).
Is the chip damaged even if the output pins in the neighborhood still work correctly?
What happened here… any idea?
thanks in advance and greetings from Germany


What are the IO numbers?


the IO numbers are for example:
IO62, // chip pin53
IO63, // chip pin55
IO65, // chip pin57
IO39 // chip pin69

chip pin56 (IO64) is working correctly.
They all semm to be on Port 1 of the chip.
Do you have any idea?
thx in advance.


There is nothing special with these pins.There must be something wrong either in the application code or in the hardware.

Try a simple application that toggles the pin and check it with a scope.


The problem is that the same design and code worked with earlier pcbs before. Now we’ve build new ones and we get this error. Can the chip be damaged? Why do we measure approx 2,3V… Is this a voltage coming from the chip when the port is uninitialized and this way configured as an input in order not to damage possible external components?


with the board off, measure continuity to see if you have solder bridges or something else weird going on. Compare your findings with those of the other board that didn’t exhibit this behaviour. What about resistors in this part of the circuit, is there anything that could be having an impact ?

I still agree though, go back to a simple code test setting a port on for 5 secs, off for 5, on for 5, etc etc and measure on all pins. This removes a lot of variables at once!

Given Gus said “or hardware”, I reckon examining the hardware more will tell you…