From 9decdcc89c4f3124686f078230f1388024b6d722 Mon Sep 17 00:00:00 2001
From: "Ben V. Brown" <Ralim@Ralimtek.com>
Date: Mon, 23 May 2022 22:25:00 +1000
Subject: [PATCH] Scratch out resistance awareness of the tip

---
 source/Core/BSP/Magic/BSP.cpp | 29 +++++++++++++++++++++++------
 source/Core/Drivers/USBPD.cpp |  4 +++-
 source/Core/Drivers/USBPD.h   |  1 +
 3 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/source/Core/BSP/Magic/BSP.cpp b/source/Core/BSP/Magic/BSP.cpp
index f4bc5772..42d9f75c 100644
--- a/source/Core/BSP/Magic/BSP.cpp
+++ b/source/Core/BSP/Magic/BSP.cpp
@@ -6,10 +6,12 @@
 #include "Pins.h"
 #include "Setup.h"
 #include "TipThermoModel.h"
+#include "USBPD.h"
 #include "configuration.h"
 #include "history.hpp"
 #include "main.hpp"
 
+
 // These control the period's of time used for the PWM
 const uint16_t powerPWM         = 255;
 const uint8_t  holdoffTicks     = 5; // This is the tick delay
@@ -224,7 +226,7 @@ void setStatusLED(const enum StatusLED state) {
   // Dont have one
 }
 
-uint8_t  lastTipResistance = 75; // default safe
+uint8_t  lastTipResistance = 80; // default safe
 uint32_t lastTipReadinguV  = 0;
 uint8_t  getTipResitanceX10() {
   // Return tip resistance in x10 ohms
@@ -241,9 +243,10 @@ void startMeasureTipResistance() {
   // If tip is connected, and the tip is cold and the tip is not being heated
   // We can use the GPIO to inject a small current into the tip and measure this
   // The gpio is 5.1k -> diode -> tip -> gnd
-  // Which is around 0.65mA this will induce:
-  // 6 ohm tip -> 3.9mV (Real world ~= 3320)
-  // 8 ohm tip -> 5.2mV (Real world ~= 4500)
+  // Source is 3.3V-0.5V
+  // Which is around 0.54mA this will induce:
+  // 6 ohm tip -> 3.24mV (Real world ~= 3320)
+  // 8 ohm tip -> 4.32mV (Real world ~= 4500)
   // Which is definitely measureable
   // Taking shortcuts here as we know we only really have to pick apart 6 and 8 ohm tips
   // These are reported as 60 and 75 respectively
@@ -263,7 +266,21 @@ void FinishMeasureTipResistance() {
     return;
   }
   // newReading -= lastTipReadinguV;
-  MSG("Tip Delta %lu, %lu %lu \r\n", newReading - lastTipReadinguV, newReading, lastTipReadinguV);
+  // MSG("Tip Delta %lu, %lu %lu \r\n", newReading - lastTipReadinguV, newReading, lastTipReadinguV);
   newReading -= lastTipReadinguV;
-  lastTipReadinguV = newReading;
+  // As we are only detecting two resistances; we can split the difference for now
+  uint8_t newRes = 0;
+  if (newReading > 5000) {
+    return; // Change nothing as probably disconnected tip
+  } else if (newReading < 4000) {
+    newRes = 60;
+  } else {
+    newRes = 80;
+  }
+  if (lastTipResistance != newRes) {
+#ifdef POW_PD
+    USBPowerDelivery::triggerRenegotiation();
+#endif
+  }
+  lastTipResistance = newRes;
 }
\ No newline at end of file
diff --git a/source/Core/Drivers/USBPD.cpp b/source/Core/Drivers/USBPD.cpp
index 98e99b7e..dfae270f 100644
--- a/source/Core/Drivers/USBPD.cpp
+++ b/source/Core/Drivers/USBPD.cpp
@@ -66,7 +66,9 @@ bool USBPowerDelivery::fusbPresent() {
 }
 
 bool USBPowerDelivery::isVBUSConnected() { return fusb.isVBUSConnected(); }
-
+void USBPowerDelivery::triggerRenegotiation() {
+  
+}
 bool pdbs_dpm_evaluate_capability(const pd_msg *capabilities, pd_msg *request) {
 
   /* Get the number of PDOs */
diff --git a/source/Core/Drivers/USBPD.h b/source/Core/Drivers/USBPD.h
index 7e27dbea..fe55fdc0 100644
--- a/source/Core/Drivers/USBPD.h
+++ b/source/Core/Drivers/USBPD.h
@@ -19,6 +19,7 @@ public:
   static bool    negotiationHasWorked();  // Has PD negotiation worked (are we in a PD contract)
   static uint8_t getStateNumber();        // Debugging - Get the internal state number
   static bool    isVBUSConnected();       // Is the VBus pin connected on the FUSB302
+  static void    triggerRenegotiation();  // Trigger a restart of voltage selection
 private:
   //
   static int detectionState;