Where to begin?

I'll leave this for a bit, to see if anyone else chips in… as for debugging, I just keep uploading to the module! There's often some head-scratching as things don't tend to work first time

This book was mentioned here on the forum a number of times: Arduino for Musicians by Brent Edstrom.

global.oup.com/academic/product/arduino-for-musicians-9780199309320?cc=au&lang=en

yes that book is really a goldmine.

There are some caveats that the book cover, especially the problem Arduinos have with floating point calculations, which are so slow that it is a no go in audio applications.

it also has lots of good examples.

Nice reading.

And the 8:8 fixed point notation is exactly what is covered in the Arduino for musicians book.

Good question! I had forgotten that I had disabled this functionality (since my libraries reassign the timers, the functionality of millis() wasn't correct).

(I also must produce documentation for the APIs, you are right to highlight this. I'm very glad that someone else is interested in writing code - my initial impression was that most people are interested in simply using pre-existing firmware)

The way that I tend to do timing is to increment a (volatile) counter in the sample-rate interrupt routine, which can then be read by code elsewhere - you then get an idea of 'ticks' to show elapsed time (there is a SRATE macro defined which reflects the selected sample rate).


/*
* Elapsed time
*
* modified Feb 2022 by John Tuffen
*
*/

#include "wonkystuffCommon.h"


volatile uint16_t wsTimeUpper;
volatile uint16_t wsTimeLower;

// the setup function runs once when you press reset or power the board
void
setup(void)
{
 wsInit();                 // general initialisation
 wsInitPWM();              // output 1 is now controlled by PWM
 wsInitAudioLoop();        // initialise the timer to give us an interrupt at the sample rate
                           // make sure to define the wsAudioLoop function!
}

// the loop function runs over and over again forever
void
loop(void)
{
 uint16_t secondsSinceStart = sayKidsWhatTimeIsIt() / SRATE;
 
}

uint32_t
sayKidsWhatTimeIsIt(void)
{
 cli();
 uint32_t now = wsTimeUpper << 16 | wsTimeLower;
 sei();
 return now;
}

// This ISR is running at the rate specified by SR (e.g 50kHz)
void
wsAudioLoop(void)
{
 // Audio code goes here…
 //
 // …
 // …

 // Increment the timing info:
 wsTimeLower++;
 if (wsTimeLower == 0)
 {
   wsTimeUpper++;
 }
}

If you have only a single reader of the time, and you just need to count ticks before a subsequent action, you can simply reset wsTimeLower to zero when you want to 'start' the timer, and then wait until the appropriate number of ticks have elapsed (bearing in mind the limited size of datatypes; e.g. a uint16_t will only count up to 65535 so will only be able to time up to 1.3 seconds at a 50kHz sample rate).

The delay() APIs are still available if you need to just insert a delay between two events (although this will be affected by code running in the interrupt routines).

Thank you namke for the answers and examples. I learned quite a bit with some additional reading. This was really interesting. I have some questions.

Which pins do the 3 CV inputs correspond to? Let's say I want to detect triggers on all 3 would it be something like this? Here I'm assuming that PB3 = CV input C and PB4 = CV input D.


volatile uint8_t clockHappenedB = 0;
volatile uint8_t clockHappenedC = 0;
volatile uint8_t clockHappenedD = 0;


void
setup(void)
{
 wsInit();                 // general initialisation
 wsInitPWM();              // output 1 is now controlled by PWM

 GIMSK |= (1 << PCIE);     // turns on pin change interrupts
 
 PCMSK |= (1 << PCINT2);   // turn on pin-change interrupts on pin PB2 (pin 7/input B on the panel)
 PCMSK |= (1 << PCINT3);   // turn on pin-change interrupts on pin PB3
 PCMSK |= (1 << PCINT4);   // turn on pin-change interrupts on pin PB4
 
 wsInitAudioLoop();        // initialise the timer to give us an interrupt at the sample rate
                           // make sure to define the wsAudioLoop function!
}

// some things happen here
...
...
...


// Pin change interrupt
// We are listening for the PCINT0_vect interrupts (i.e. pins of the PB group).
ISR(PCINT0_vect)
{
   // Check the bit of the PB status register corresponding to one of the pins
   if (PINB & _BV(PB2))
   {
       clockHappenedB = 1;
   }

   if (PINB & _BV(PB3))
   {
       clockHappenedC = 1;
   }

   if (PINB & _BV(PB4))
   {
       clockHappenedD = 1;
   }
}


This is super useful! I was wondering about the absense of ‘millis()’ also, just hadn’t got round to asking