Need more than 16 digital outputs

JackieWD

Hi, I am a beginner of Bela!
In my project, I need more than 20 digital outputs to control the switch on/off of mutiple relays, which connect to a circuit of higher voltage (48V). I am wondering how I can expand the number of digital outputs on Bela (16 max as far as I know)?

I have some ideas, but I am not sure whether they are feasible:
1) use some analog outputs as digital outputs?
2) any multiplexer for expanding digital output?
3) try to use shift register?

Hope someone can give me some advice, Thanks!

giuliomoro

JackieWD 3) try to use shift register?

this is a good option, there is an example that does just that: https://github.com/BelaPlatform/Bela/tree/master/examples/Sensors/shift-register-out

You could also use some of the spare pins using the Gpio class, see this page for further information.

JackieWD

Thank you giuliomoro!
I am working on puredata. For the first option, how can I implement the cpp code in pd? Is there a good example in pd as well?

I've read the instruction for setting GPIO, is it also accessed through cpp? How can I get the index of extra GPIO pins in pd? Take bela mini as an example, what should I do if I want to set the p2.03 / 05 / 07 / 09 as digital I/O?(https://raw.githubusercontent.com/wiki/BelaPlatform/Bela/Images/BelaMiniPinout.png)

giuliomoro

JackieWD or the first option, how can I implement the cpp code in pd?

you need to integrate some C++ code in a custom libpd_render file. This is explained in some detail here, Unfortunately, you need some knowledge of C++ to implement this solution ... unless ... that's going to take me a while to help you with this ... give me a week or so then ping me again