Just tried to configure my shutter. I'm using an opto-isolator with CHDK functionality. The idea is that I should be able to pull a pin high for a specified number of ms, configure a CHDK script to measure the time that it's raised and then take a photo or shut down the camera.
First thing I did was see how I could accomplish this on APM 2.6. This page seems to be the best description, others mostly describe doing this with PWM signals:
It states that A9 is raised high when the shutter is configured as "relay". I've set the time to something high. The maximum is 127. When the switch is low, I measure 0.00v. Then I flip the switch, but the pin isn't raised high. Ch7 is indeed set to "camera trigger" in the radio calib.
One strange thing in this config is that when I change the page from "camera gimbal calibration to something else and then go back, the config in the camera trigger part has disappeared. Not sure if therefore it actually did get saved.
The pin I'm measuring is A9 and on the APM2.6, I'm counting from A0 to A9. That leaves A10 and A11 on the rest of the end and 2 additional pins that are NC. So it's the fifth from the forward end.
Has anyone gotten this to work properly? What am I doing wrong or is this documentation wrong?