From 1a2ce7e7c0f58428e861b81e381bfe7ca7d0a47b Mon Sep 17 00:00:00 2001
From: lucavanstraaten <lucavanstraaten@local>
Date: Tue, 28 Apr 2026 21:18:35 +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 1ab47fa..9a76a36 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -41,6 +41,24 @@ 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(uint64_t value, uint64_t maxVal) {
+  if (maxVal == 0) { setStatus(16, 0, 16); return; }  // magenta = unknown range
+  uint16_t hue = (uint16_t)((value * 360) / maxVal);  // 0-359
+  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;
+  }
+}
+
 // =========================================================================
 // CORE 1: SSI worker
 // =========================================================================
@@ -105,6 +123,7 @@ void requestSsiRead(uint8_t bits, uint16_t half_us, uint64_t& outValue, uint32_t
 
 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;
   }
@@ -112,6 +131,7 @@ 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;
   }
@@ -120,19 +140,24 @@ void handleCommand(const String& cmd) {
   int halfUs = cmd.substring(secondSpace + 1).toInt();
 
   if (bits < 1 || bits > 64) {
+    setStatus(16, 0, 0);  // red = error
     Serial.println("ERR bits must be 1..64");
     return;
   }
   if (halfUs < 1 || halfUs > 10000) {
+    setStatus(16, 0, 0);  // red = error
     Serial.println("ERR half_us must be 1..10000");
     return;
   }
 
-  setStatus(0, 0, 16);                             // blue = reading
+  setStatus(0, 0, 16);  // blue = reading
   uint64_t value;
   uint32_t took;
   requestSsiRead((uint8_t)bits, (uint16_t)halfUs, value, took);
-  setStatus(0, 16, 0);                             // green = idle
+
+  // Show encoder position as hue (full range = 2^bits - 1)
+  uint64_t maxVal = (bits < 64) ? ((1ull << bits) - 1) : UINT64_MAX;
+  setPositionColor(value, maxVal);
 
   Serial.printf("OK bits=%d half_us=%d hex=0x%llX dec=%llu took=%luus\n",
                 bits, halfUs, value, value, took);