Sharing Tx (pin30) Rx(pin31) with other circuits that is using pull up.
tonyp12
Posts: 1,951
I'm building a RTC module that will use pin 28 & 29 to share the I2C bus.
Pin-out is loosely based on Gadget Gangsters propboard.
So between pin28 and Vdd you have Rx/Tx pins, that I will use for RTC interrupt
Should I use pin 30 or 31?
For the RTC interrupt that is open drain,
active low and uses 10k-47k pull-up resistor
The INT pin stays low until all intflags are cleared by software.
So I don't want it to be a chance where you could brick the system if
you are still programming the setup with a USB/Serial cable and it
stops responding to proptool.
BTW is Rx/Tx open drain?, there are internal pull ups in the FTDI chip?
Pin-out is loosely based on Gadget Gangsters propboard.
So between pin28 and Vdd you have Rx/Tx pins, that I will use for RTC interrupt
Should I use pin 30 or 31?
For the RTC interrupt that is open drain,
active low and uses 10k-47k pull-up resistor
The INT pin stays low until all intflags are cleared by software.
So I don't want it to be a chance where you could brick the system if
you are still programming the setup with a USB/Serial cable and it
stops responding to proptool.
BTW is Rx/Tx open drain?, there are internal pull ups in the FTDI chip?
Comments
P30 is an output pin although I am unsure if it is made so until the download sequence is detected. It is not open drain, so you may also have a conflict here too.