pickman555 1. afaik, I need to plug bela with usb to laptop and click "build & run" on the ide, is there a way to use a power cable to start bela and run a certain project automatically?
in the IDE, at the top of the settings tab there is a dropdown to set a project to run on boot. Select your project there and when the board starts up again, that project will run automatically (typically within 10 seconds of power up). Note that:
- any options for the program need to be set before setting the program to run on boot
- if the program that runs on boot takes up a significant amount of CPU, it may take very long for the IDE to come up while the program is running. For this reason it may be useful to either make the Bela button accessible from the outside, or remote the corresponding pin (P9.27 on Bela, P2.34 for BelaMini) to the case with some wires. Connecting this pin to ground will stop the running program.
pickman555 2. The bela input & output have 3.5mm aux, I need an aux adapter from 3.5mm to 6.35 mm for a guitar PL?
The best option is often to remove the existing 3.5mm connector and solder the wires directly to the 1/4 inch connector.
In most cases (i.e.: if you are going into a distortion or other non-linear effect without an external band-limiting pedal (e.g.: EQ) pedal before), you will probably also want an additional low-pass filter on the audio output: install an RC low-pass filter (resistor in series, capacitor to ground) for each channel, using as values R = 390ohm and C = 22nF if using the headphone out or R = 4.7k and C=2.2nF if using the line out (J9 on Bela). This is to avoid the high-frequency (beyond audio range) noise present at the output of the sigma-delta converter from being somehow aliased back into the audio range from the non-linearity of the next stage.
