Hi,
Here are a couple of projects that might be of interest for anyone starting a project using MPR121 boards and Pure Data on Bela (with libPD).
https://github.com/luiszayas/kazumi/tree/master/software/MPR121_pd
https://github.com/luiszayas/kazumi/tree/master/software/MPR121_pd_multiple
I think you need a space between 11 and ~ when sending to bela_setDigital: double check against the example. To make sure you are generating the expected signal, you could connect the digital output back to an analog input with a wire and send the new analog input to the scope ([dac~ 27 28 29 30]).
However, the digital outputs are 3.3V. The (minimal) datasheet indicates "Voltage: 4.8V - 6V", so I would try to send a 5V signal, instead of 3.3V. You could either use a transistor to do level shifting on the digital outputs or use the analog outputs, which are 5V. These can be addressed with [dac~ 3] to [dac~ 10] from PureData.
