This is an ESP-32 based ftms-server which I edited for my Schwinn IC7 bike. Originally built for jamesjmtaylor's stationary bike stand. It uses the Indoor Bike Data characteristic of the FTMS BLE service.
I used platformio plugin for VSCode to compile and upload the firmware to a D1 mini ESP32
I added two 1k resistors: one soldered to GPIO27 and one to the GND next to it to avoid breaking the board.
Then I splitted a 0.5m mono cable with 3.5mm jack into half
!!! MAKE SURE TO USE A CABLE WITH ONE MALE AND ONE FEMALE PLUG !!!
and drilled the wires together and soldered them to the resistors on the board.
This is how it looks like
Then you can connect it to your bike without harming the IC7
just disconnect the display from the sensor and plug the D1 mini ESP32 in between - et voilá - your IC7 speaks FTMS now.
Ready to connect to Zwift, WahooRGT or similar...
actually it is powered with 5v via the usb jack - but I'm planning to add a rechargeable battery and a shield for charging... and last but not least a little case to fit.
have fun!