Xtend GPIO characteristics


#1

Does anyone know the electrical characteristics for GPIO21/25 on the Xtend power cable ? These are referenced to Vref (I’m using 5.0V) and appear to have pretty strong internal pull-ups (I’m using them as inputs connected to open-collector opto-couplers). I’ve managed to get something working but its been trial and error and not satisfactory.


#2

There are details in the current User Guide…


#3

To finish this story - I’ve set Vref to 5.0V and pulled each GPIO down to Gnd using 1K8 resistors. PS2811 opto-couplers pull up the GPIO when required. One of the GPIO (21) seems to be set as an output (pulled strongly high) for quite a few seconds while the modem starts up, but there’s nothing I can do about that.


#4

I have a similar problem on the GPIO, according to the user guide it is suggested to tie the Vref for the IO voltage to a fixed voltage ie 5.0v. however if i measure the high value of the GPIO it goes only as high as 1.8V in a output mode it never reaches the 5.0v level. is there any specific trick to get it to the level of the vref?


#5

Hi,

Please ignore the post, the GPIO pin doe go to the Vref if no load is available however the pin is pulled high through a 100k resistor to vref which makes the current flow verry little and not enough to drive what i needed it to drive.
regards