Since I also wish to develop a physical interface in addition to the OSC control, I built a prototype to experiment with the possibilities. I want to keep the interface as simple as possible, so I set up only 4 potentiometers that allow the control of one effect at a time. To read the potentiometers from the analog inputs on Bela, I had to add a piece of code for each input in PD. As Bela handles analog inputs just as audio signals at the sampling rate, I had to set up an [adc~] object for each potentiometer respectively. The first 2 channels are reserved for the audio signal, but from 3 to 10, I was able to access the required analog inputs.
To convert the incoming values into numbers, I used the [snapshot~] object which takes a signal and converts it to a control value whenever it receives a bang in its left inlet. To make it output the value constantly, I connected a [metro] object to it, which bangs it continuously at a specified rate. After receiving a value between 0 and 1 from each potentiometer, I could already control all parameters manually. For those that need a range other than 0 to 1, I set up math calculations to translate the values to the required ones. Next, I set up a structure that routes the corresponding set of values to the selected effect.
To choose which effect is set on the physical interface I added a button to each unit in the OSC interface. These are then connected to their respective [spigot] objects in PD, which only pass the signal when the switch is on, thus routing the control values to the selected effect. Because the analog input values come in at a constant rate, they immediately force their initial value on the selected parameters. This leads to a conflict with the OSC interface as its values are always forced to the analog ones. To solve this problem, I implemented an if statement for all parameter sets, which immediately disconnects the physical interface in case there is a change within the OSC interface of the respective effect.