How to control bi-directional logic line bypassing the open-collector stage?
The reset line on the module has a strange design to be a true bi-directional reset line. And indeed it is not really a bi-directional reset line. The diode in series with the pin on the module makes the RESET_N pin on the module be only a RESET input signal to the module. In the other direction the module cannot pull down the signal at all and will depend on an EXTERNAL pulldown impedance. So what happens is that the module is able to pull the RESET_N signal pin to a high level of 1.88V minus a shottkey diode drop when the module is powered up and active. The module integration guide specifically says that when you want to be able to detect the status of the module that the value of the pull down resistor needs to be at least 680K ohms.