From 13789932cba6e2cb0e4ccf238b399fdccb3ae6be Mon Sep 17 00:00:00 2001
From: JP Stringham <jp@bloomdigital.to>
Date: Tue, 27 Jan 2026 10:42:04 -0500
Subject: [PATCH] Current stepping via transistor DAC

---
 src/main.rs | 72 +++++++++++------------------------------------------
 1 file changed, 15 insertions(+), 57 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 57377eb..01da68f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -35,9 +35,6 @@ pub static BOOT2: [u8; 256] = rp2040_boot2::BOOT_LOADER_GENERIC_03H;
 /// if your board has a different frequency
 const XTAL_FREQ_HZ: u32 = 12_000_000u32;
 
-// below this we won't be able to turn on the transistor (0.6v)
-const MIN_DUTY: u16 = 6000;
-
 #[rp2040_hal::entry]
 fn main() -> ! {
     // Grab our singleton objects
@@ -79,33 +76,19 @@ fn main() -> ! {
         .clock_divider(47999, 0)
         .start_paused();
 
-    let mut pwm_slices = hal::pwm::Slices::new(pac.PWM, &mut pac.RESETS);
-
-    let pwm = &mut pwm_slices.pwm2;
-    // info!("PWM Top: {}", pwm.get_top());
-    pwm.set_ph_correct();
-    pwm.enable();
-
-    let pwm_channel = &mut pwm.channel_a;
-    pwm_channel.output_to(pins.gpio20);
-    pwm_channel.set_duty_cycle(MIN_DUTY);
-
-    // calibrate
-    delay.delay_ms(2000);
-
     // let mut led_pin = pins.gpio25.into_push_pull_output();
 
-    let mut duty = MIN_DUTY;
-
-    let mut power = 0;
-
-    let mut tick = 19u8;
+    let mut tick = 0u8;
 
     let mut peak_v = 0u32;
 
-    loop {
-        pwm_channel.set_duty_cycle(duty);
+    let mut current_pins = [
+        pins.gpio16.into_push_pull_output().into_dyn_pin(),
+        pins.gpio17.into_push_pull_output().into_dyn_pin(),
+        pins.gpio18.into_push_pull_output().into_dyn_pin(),
+    ];
 
+    loop {
         delay.delay_ms(500);
         adc_fifo.clear();
         adc_fifo.resume();
@@ -116,42 +99,17 @@ fn main() -> ! {
 
         adc_fifo.pause();
 
-        let mut samps = [0u16; 8];
+        for (i, cp) in current_pins.iter_mut().enumerate() {
+            let mask = 0b1 << i;
 
-        for i in 0..8 {
-            samps[i] = adc_fifo.read();
+            if mask & tick > 0 {
+                cp.set_high();
+            } else {
+                cp.set_low();
+            }
         }
 
-        let avg = avg_fifo(&samps, false);
-        let voltage = (avg * 3300) / 4095;
-
-        let duty_as_pct = (duty - MIN_DUTY) as u32 * 100;
-        let duty_as_pct = duty_as_pct / (0xFFFF - MIN_DUTY) as u32;
-
-        let new_power = (voltage * (1 + voltage / 100)) * duty_as_pct;
-
-        tick = (tick + 1) % 20;
-
-        if tick == 0 {
-            info!(
-                "{} duty, {}mV, {} power, {} peak",
-                duty_as_pct, voltage, new_power, peak_v
-            );
-        }
-
-        if duty_as_pct == 0 || voltage > peak_v {
-            peak_v = voltage;
-        }
-
-        duty = duty.wrapping_add(1000);
-        duty = MIN_DUTY.max(duty);
-        // if voltage > (90 * peak_v) / 100 || new_power >= power {
-        //     duty = duty.saturating_add(33);
-        // } else {
-        //     duty = MIN_DUTY.max(duty - 32);
-        // }
-
-        power = new_power;
+        tick = (tick + 1) % 8;
     }
 }