DIY: fixing the TI brand port expander chip

sigh. 'plug compatible' should always be viewed with suspicion.

 

supposedly, the TI (texas instruments) and philips (NXP) parts are the same. but they're not!

 

the TI version needs pullup resistors or it just will NOT work! the NXP part does not need them.

 

I did all my testing (up to now) with NXP and it was a good thing I tried the TI part else I would not have known about these NEEDED pullups!

 

the pullups were hacked in as resistor networks (yellow things) across the output of the PE chips and bussed to Vcc as a normal pull-up would do.

Done