I want to use the Pi to “snoop” on an SD Card that is inserted into another device (dev1). I did some research on the net and so far I have not found any nice solution to do so:
Dev1 has an SD card inserted and is writing from time to time (exactly every minute) small text files onto the card. The RPI needs to read those textfiles and do something with them (e.g. send via ethernet).
The only idea that I came up so far was to use an SD-card extension cord, split it up and connect one side to an usb-card reader so that both devices are connected to the sd card simultaneously. Then I somehow would have to be able to tell when dev1 is not writing (which could be done via GPIO) and read from the card. However, I am not sure if that even could work so simple as the devices might interfere with each other. I could use some relays (from an extension board) to disconnect the card detection lines. However, this whole concept seems to be a little bit fragile.
Does anybody have an idea to solve this a better way?