Simple program for the ESP32 (ESP32-C3 in this instance) that allows you to connect to switches that will act as the previous track and play/pause media buttons over Bluetooth.
I created some simple pedals with aluminium foil on card board and a bit of foam at one end, so that they are normally separated, but pushing at the other end creates contact between the two pieces of foil. The play/pause button is connected on pin 8, the previous track button on pin 6 and the other wires of both switches to ground.
In Windows you should forget the device before unplugging and repairing it every time, otherwise it won't get a stable connection. (At least that's my experience.)
On Windows, I found that this fork of Media Player Classic - Home Cinema works best. The built in media players don't have hotkeys to skip back a few seconds while in the background and VLC has some delays when hitting play/pause quickly and occasionally skips a few seconds. To make the skip back key work, you need to modify the hotkeys under Options > Player > Keys for the command Jump Backward (I chose the medium one). In the App Command column, choose MEDIA_PREVIOUSTRACK, and make sure the Global Media Keys option at the bottom of the window is checked. Remove the MEDIA_PREVIOUSTRACK value from the normal Previous command. (For symmetry, you may also choose to modify the Jump Forward command similarly.)
I have a couple of these boards, which are a little special. The ESP32-C3 has a RISC-V processor, rather than the ARM chips found in other ESP32 modules. The ones I have are the (d) type, with only 2M of flash storage, rather than the usual 4M. Since this board is unknown to PlatformIO, I use the c3-devkit board and set the following settings:
monitor_rts = 0
monitor_dtr = 0
board_upload.flash_size = 2MB
board_build.partitions = esp32c3-2m-partitions.csv
board_build.flash_mode = dioThe rts and dtr flags are required for the serial monitor to work on these boards, and the C3 in general seems to require the dio flash mode. For the special size, I set the flash_size option and used a custom partition table.