I’m using AirPrime Q2687 module and I configured GPIO4 port as input. This input is GND active input so It’s mean that input is in high state when no activ and switch to low state when active.
The problem is: I’m changing input values on GPIO4 line, but read value of this input is constantly high. In documentation is said that port GPIO4 is reset by pull-up so I think that this pull-up is to strong and prevent change state to low.
Is it possible to turn off pull up or configure It at any way?
If not, maybe there is another way to read correct values?
I searched manuals and specs but didn’t find informations what I need.
You should easily be able to check if that is really the case with a simple measurement…
I think not.
The point is, that I did measurements and modem hold high state all time.
So there is no software solution? And what about hardware solution?
You didn’t mention that.
Have you measured the pull-up current?
Yes, I didn’t sorry. I only said that state is high. I measured pull-up current, In attachment there is piece of schema where I did measurements. On the left site is input, from right side we have line directly to GPIO4 AirPrime port. Transistor Q20 is switching circuir depending on state of input. This two resistors on the right side should pull voltage to the ground. It doesn’t happen because voltage from GPIO4 is to high. After change R165 and R910 to 10k both, everythink starts work correctly. I wish to do thing without that changes if It possible.
Why the potential divider?
100k sounds a bit high to me for any microcontroller input?!
The module has 1.8V tolerant input, hasn’t it? The input to the device can be more than 30V, so we need some kind of trick here. The divider from 3.3V gives us 1.65V and 100k isn’t that bad for a high-z input. Moreover if you use smaller resistors the power consuption increases, which is what we don’t want to do.
So if we disable pull-up - that’s the best solution, well known in microcontrollers. If not - we’ll have to change our layout or agree for higher power consumption.
Did you solve your problem with GPIO4 in Q2687?
I’m having the same issue with that module: the voltage at input is zero, but module read 1.
I use this configuration (firmware v7.47.4):
“DWL”,“V08b13”,"",“Sierra Wireless”,55344,“111611 18:03”,“dda36757”,“00010000”
“FW”,“FW_SRC_747_8_F4_3.Q2687G”,“R184.108.40.206208311102.Q26CL702”,“Sierra Wireless”,2221264,“083112 11:02”,“6aa633a2”,“00020000”
Could it be a problem of firmware?