Particle Agent breaks I2S functionality on Raspberry Pi Zero and 3

The Archive Raspberry Pi
1

Hi
I’m using an I2S amplifier


for sound output which connects on
GPIO18, GPIO19 and GPIO21
Immediately the Particle Agent is installed the sound stops - no reboot required
I’ve tested on Raspberry Pi Zero and 3
Do you guys have a solution to either disabling Particle Agent from taking over pins? - or returning pins to OS control? - I suspect the later may be the route to immediate solution
Regards
Julian

2

Hi Julian,
We face the same problem with the Adafruit Speaker Bonnet. When one installs the Particle Agent also for this I2S device the music stops…

I have struggled trying to find an option to disable specific pins, but was unsuccesfull so far.

Edge

3

URL is by the way https://www.adafruit.com/product/3346

4

I would presume that stopping the particle-agent service would restore the I2S functionality?

5

Hi Kenneth

Good question - no it doesn’t

sudo particle-agent stop
speaker-test -c2

Silence

However if I

rm /var/lib/particle/devices/xxxxxxxxxxxxxxxxxxxxxxx/firmware.bin
sudo reboot
sudo particle-agent status

Shows service is running

speaker-test -c2

Sound working

What does this prove? - the Particle Agent is not part of this problem - the problem is entirely in the firmware image - in the initialization code - as soon as the firmware runs - it kills the I2S - stopping the firmware and the agent - doesn’t fix it - rebooting - and not running the firmware - but running the agent - “fixes” the problem

Also copying the firmware.bin file back immediately kills the I2S as the Particle Agent notices it’s back and immediately starts it up - robust!

Regards

Julian

6

If in setup you do the following:

void setup() {
 pinMode(A7, OUTPUT); //pin 40 on Rpi
 pinMode(D7, OUTPUT); //pin 35 on Rpi
 pinMode(A0, OUTPUT); //pin 12 on Rpi
}

can you check if it works? by first running the particle firmware and agent then start the speaker again.

Not sure if there’s a “lock” that only allows one process to access the GPIO pins but it might be worth just giving it a try :slight_smile:

I based the I2S connection pins on the schematic: https://learn.adafruit.com/assets/37882

7

Hi Kenneth and Edge

I’ve tried that - no go

However that is the right direction - I’ve found a workaround

Install WiringPi

sudo apt-get install git-core
cd ~
git clone git://git.drogon.net/wiringPi
cd wiringPi
./build

then run these commands

gpio mode 1 alt0
gpio mode 24 alt0
gpio mode 29 alt0

and I2S functionality returns - the pins will be broken any time the firmware starts - either on boot - or on flashing - so these commands should be run in setup function

Regards

Julian

8

I hope the workaround is a good start. :slight_smile:

Eventually, it will be great to have this finer grain control in the firmware!

1 Like
9

You could make a script that runs these commands and call the script in your setup using Process Control.

https://docs.particle.io/reference/firmware/raspberry-pi/#process-control

10

Hi

I have streamlined this solution - as WiringPi is already in the Raspberry Pi firmware I’m able to call the function directly as below

extern "C" void pinModeAlt (int pin, int mode);
#define ALT0 0b100

void setup () {

  // Restore I2S pins

  pinModeAlt (GPIO18, ALT0);
  pinModeAlt (GPIO19, ALT0);
  pinModeAlt (GPIO21, ALT0);

Regards

Julian

2 Likes
11

Based on the discussion here, I’m planning on changing the behavior of the pin initialization on the Raspberry Pi. Thanks for the feedback!

2 Likes
12

Check Raspberry Pi: Pre-release firmware with improved pin initialization to try the new behavior.