Moving a project from Arduino to Raspberry Pi Zero

[aiq25]

Hello. I'm working on a project that is currently using an Arduino but I would like to move it to a Raspberry Pi Zero. I think using the Pi Zero will be less hassle.

Currently I have the following modules interfaced with an Arduino Nano: RTC, graphics LCD, SD card. Basically it's a fancy clock module with some added features. The reason I would like to move it to the Pi Zero is because I would like to be able to play large audio files with the module. I kind of got this working with the Arduino but I would like to try it on the Pi Zero. I would also like to use a bigger screen using the AV output of the Pi Zero.

Are there any beginner tutorials anyone can recommend? I don't have any experience programming in Python or the Pi Zero. I have only worked with microcontrollers.

[ealex]

short answer : it will be complicated.

long one:
i imagine you'll use the entire linux OS for it and not as a bare-bone system.

the main code will run the same but you'll have to change the entire IO stuff:
- no more raw access to RTC - you'll have to use C time functions or learn how to use
I2C / SPI linux drivers or, if you're lucky you might be able to install a kernel module for your RTC so you can see it in /dev/ or make the OS use it as the main clock
- no more raw access to LCD, etc
- the same for user IO - you'll have to use GPIO system and learn how to enable / disable GPIO's and make the C code react on events
- no more raw access to audio, etc - you'll have to spawn a mplayer process or something to play your audio file

basically you'll have to learn everything from scratch.
C experience will help a lot, but still you'll have to learn the external libraries / etc

some other disadvantages :
- you'll have to take care of the entire OS including specific SD wear problems / updates / install / etc
- greater cost
- greater power usage


i'm doing the reverse of what you want:  i'm using a RPI as a dev. system for some pulse-oximeter related code that will finally run on a cortex M0 micro.
to make porting possible :
- i made the low level I2C access as generic read / write functions that will be replaced with MCU specific code
- all debug information on screen is generated from macros that i can change / disable easily
- all data dumps are also handled by functions that can be disabled without changing the main code
- i've used types from "stdint.h" - that are equivalent between system : uint32_t is an unsigned 32bit integer even if i'll build that code for a Z80

[brucehoult]

If your only real problem is not enough storage space for large audio files then I think you'll have a LOT less trouble sticking to an Arduino and just adding an SPI flash chip or SD card. Or buying a "Arduino" with one built in.

[hamster_nz]

The way I would approach this with a Raspberry Pi is quite different to Arduino.

- Get a Pi Zero W (with Wireless)

- Use NTP to get the time over wireless, I would not use a RTC. Automatic timezone changes.

- Use OpenGLes to do the display - making use of the GPU (see https://github.com/peepo/openGL-RPi-tutorial for tutorial code). This will be the biggest challenge to learn.

- Play audio files by fork()ing a process to play the audio streams

- Use basic GPIO for any required local user interface (buttons/switches)

- Do development remotely on the Pi over SSH.

You can find some very poor C code to see how to use GPIO and I2C at its lowest userspace levels at http://hamsterworks.co.nz/mediawiki/index.php/Raspberry_Pi - it is very old but you should get the gist especially for GPIO- you open a couple of special files and read/write values to them. One controls the pin direction (input vs output), the other reads the current value of the pin.

This is all very old-school, but then I am that sort of guy.