From a618cb238fdbc4a9f09debb631aaee13ac16e0c7 Mon Sep 17 00:00:00 2001
From: lucavanstraaten <lucavanstraaten@local>
Date: Tue, 28 Apr 2026 21:16:59 +0200
Subject: [PATCH] LED: show encoder position as hue after each read

- Add setPositionColor(): maps SSI value to HSV hue (0=red, 120=green, 240=blue)
- LED takes the position hue as its resting colour between reads
- Blue during active read unchanged
- All error paths now flash red before printing ERR
---
 src/main.cpp | 29 +++++++++++++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)

diff --git a/src/main.cpp b/src/main.cpp
index ac873bc..547f7e5 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -27,6 +27,25 @@ void setStatus(uint8_t r, uint8_t g, uint8_t b) {
   led.show();
 }
 
+// Map encoder position to a colour on the HSV wheel (brightness fixed at ~20/255).
+// hue 0-359: 0=red, 120=green, 240=blue
+void setPositionColor(uint32_t value, uint32_t maxVal) {
+  if (maxVal == 0) { setStatus(16, 0, 16); return; }  // magenta = unknown range
+  uint16_t hue = (uint16_t)(((uint32_t)value * 360) / maxVal);  // 0-359
+  // HSV → RGB with S=1, V=20
+  uint8_t sector = hue / 60;
+  uint8_t frac   = (uint8_t)(((hue % 60) * 255) / 60);
+  uint8_t v = 20, p = 0, q = (uint8_t)(v * (255 - frac) / 255), t = (uint8_t)(v * frac / 255);
+  switch (sector % 6) {
+    case 0: setStatus(v, t, p); break;
+    case 1: setStatus(q, v, p); break;
+    case 2: setStatus(p, v, t); break;
+    case 3: setStatus(p, q, v); break;
+    case 4: setStatus(t, p, v); break;
+    case 5: setStatus(v, p, q); break;
+  }
+}
+
 void ssi_pio_init(uint half_us) {
   // pioasm generates these helpers in ssi.pio.h
   ssi_offset = pio_add_program(ssi_pio, &ssi_master_program);
@@ -85,6 +104,7 @@ uint32_t ssi_pio_read(uint8_t bits) {
 
 void handleCommand(const String& cmd) {
   if (!cmd.startsWith("READ ")) {
+    setStatus(16, 0, 0);  // red = error
     Serial.println("ERR unknown command. Use: READ <bits> <half_us>");
     return;
   }
@@ -92,6 +112,7 @@ void handleCommand(const String& cmd) {
   int firstSpace = cmd.indexOf(' ');
   int secondSpace = cmd.indexOf(' ', firstSpace + 1);
   if (secondSpace < 0) {
+    setStatus(16, 0, 0);  // red = error
     Serial.println("ERR usage: READ <bits> <half_us>");
     return;
   }
@@ -100,21 +121,25 @@ void handleCommand(const String& cmd) {
   int halfUs = cmd.substring(secondSpace + 1).toInt();
 
   if (bits < 1 || bits > 32) {
+    setStatus(16, 0, 0);  // red = error
     Serial.println("ERR bits must be 1..32 (PIO ISR limit)");
     return;
   }
   if (halfUs < 1 || halfUs > 10000) {
+    setStatus(16, 0, 0);  // red = error
     Serial.println("ERR half_us must be 1..10000");
     return;
   }
 
   ssi_pio_reconfigure_speed(halfUs);
 
-  setStatus(0, 0, 16);
+  setStatus(0, 0, 16);  // blue = reading
   uint32_t t0 = micros();
   uint32_t value = ssi_pio_read((uint8_t)bits);
   uint32_t took = micros() - t0;
-  setStatus(0, 16, 0);
+
+  // Show encoder position as hue (full range = 2^bits - 1)
+  setPositionColor(value, (1ul << bits) - 1);
 
   Serial.printf("OK bits=%d half_us=%d hex=0x%lX dec=%lu took=%luus\n",
                 bits, halfUs, value, value, took);