From 5d8532811ed9679d7dbb01f613ca3214bb9f7366 Mon Sep 17 00:00:00 2001
From: Nolan Nguyen <nolantk.nguyen28@gmail.com>
Date: Tue, 18 Nov 2025 18:00:50 -0800
Subject: [PATCH] Implement encoder processing for keypress updates

Added encoder processing to handle rotary input and update keypress reports accordingly.
---
 firmware/modularkbd/Core/Src/main.c | 34 +++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/firmware/modularkbd/Core/Src/main.c b/firmware/modularkbd/Core/Src/main.c
index d4293687..92046843 100644
--- a/firmware/modularkbd/Core/Src/main.c
+++ b/firmware/modularkbd/Core/Src/main.c
@@ -125,6 +125,8 @@ volatile uint8_t MODE = MODE_INACTIVE;
 
 UARTMessage uartBuffer;
 volatile int uartUpdateFlag = 0;
+// Encoder state (TIM3 in encoder mode on PA6/PA7)
+volatile int32_t LAST_ENCODER_COUNT = 0;
 
 /* USER CODE END PV */
 
@@ -136,6 +138,7 @@ void UART_DMA_SendReport(UART_HandleTypeDef *huart);
 void addUSBReport(uint8_t usageID);
 void handleUARTMessages(uint8_t *data, UART_HandleTypeDef *sender);
 void matrixScan(void);
+void encoderProcess(void);
 void resetReport(void);
 void sendMessage(void);
 void findBestParent();
@@ -191,6 +194,9 @@ int main(void)
   HAL_UART_Receive_DMA(&huart2, (uint8_t*)&RX2Msg, sizeof(UARTMessage));
   HAL_UART_Receive_DMA(&huart4, (uint8_t*)&RX4Msg, sizeof(UARTMessage));
   HAL_UART_Receive_DMA(&huart5, (uint8_t*)&RX5Msg, sizeof(UARTMessage));
+  // Start TIM3 encoder (PA6/PA7) so we can read encoder delta
+  HAL_TIM_Encoder_Start(&htim3, TIM_CHANNEL_ALL);
+  LAST_ENCODER_COUNT = __HAL_TIM_GET_COUNTER(&htim3);
   /* USER CODE END 2 */
 
   /* Infinite loop */
@@ -201,6 +207,7 @@ int main(void)
 	  case MODE_ACTIVE:
 		  resetReport();
 		  matrixScan();
+		  encoderProcess();
 		  UARTMessage UARTREPORT;
 		  UARTREPORT.DEPTH = DEPTH;
 		  UARTREPORT.TYPE = 0xEE;
@@ -234,6 +241,7 @@ int main(void)
 	  case MODE_MAINBOARD:
 		  resetReport();
 		  matrixScan();//Something related to this making the key stick. Likely due to race conditions
+		  encoderProcess();
 		  if(uartUpdateFlag){
 			  for(int i = 0; i < 12; i++){
 				  REPORT.KEYPRESS[i] |= uartBuffer.KEYPRESS[i];
@@ -432,6 +440,31 @@ void matrixScan(void){
     }
 }
 
+// Read TIM3 encoder counter, calculate delta and add corresponding keycodes
+void encoderProcess(void){
+  int32_t cnt = (int32_t)__HAL_TIM_GET_COUNTER(&htim3);
+  int32_t diff = cnt - LAST_ENCODER_COUNT;
+  // TIM3 configured as 16-bit counter (period 65535). Fix wrap-around.
+  if(diff > 32767) diff -= 65536;
+  if(diff < -32768) diff += 65536;
+  if(diff > 0){
+    int steps = diff;
+    if(steps > 10) steps = 10; // cap bursts
+    for(int i = 0; i < steps; i++){
+      // CW -> KEYCODES[0][0]
+      addUSBReport(KEYCODES[0][0]);
+    }
+  }else if(diff < 0){
+    int steps = -diff;
+    if(steps > 10) steps = 10;
+    for(int i = 0; i < steps; i++){
+      // CCW -> KEYCODES[0][1]
+      addUSBReport(KEYCODES[0][1]);
+    }
+  }
+  LAST_ENCODER_COUNT = cnt;
+}
+
 void resetReport(void){
 	  REPORT.MODIFIER = 0;
 	  memset(REPORT.KEYPRESS, 0, sizeof(REPORT.KEYPRESS));
@@ -469,3 +502,4 @@ void assert_failed(uint8_t *file, uint32_t line)
   /* USER CODE END 6 */
 }
 #endif /* USE_FULL_ASSERT */
+