Document QSPI protocol findings and display fix plan

- DISPLAY_FIX_PLAN.md: root cause analysis, byte-order mismatch,
  PSRAM cache coherency issue, reference implementations studied
- axs15231b.c: QSPI protocol rewrite with correct ArduinoGFX framing
  (cmd=0x02 for regs, cmd=0x32/addr=0x003C00 for pixels)
- display.c: portrait centering for 320x480, render-on-change logic
- Makefile: Board C support (flash-c, lock-c)
- axs15231b.h: QSPI command/address constants

Display shows recognizable text, colors wrong due to byte-swap

1 files changed, 40 insertions, 3 deletions

diff --git a/Makefile b/Makefile
index 044ad6b..05c004e 100644
--- a/Makefile
+++ b/Makefile
@@ -9,6 +9,7 @@ PROJECT_DIR := $(shell pwd)
 BUILD_DIR := $(PROJECT_DIR)/build
 PORT_A ?= /dev/ttyACM1
 PORT_B ?= /dev/ttyACM2
+PORT_C ?= /dev/ttyACM0
 PORT ?= $(PORT_A)
 BAUD ?= 460800
 TARGET ?= esp32s3
@@ -45,6 +46,14 @@ define require_lock_b
         fi
 endef
 
+define require_lock_c
+        @if [ ! -f "$(HARDWARE_LOCK_DIR)/board-c.lock" ]; then \
+                echo "$(RED)$(BOLD)Board C not locked — run 'make lock-c PHASE=\"description\"' first$(RESET)"; \
+                echo "$(YELLOW)Another LLM session may be using Board C.$(RESET)"; \
+                exit 1; \
+        fi
+endef
+
 define _require_board_lock
         @if [ ! -f "$(HARDWARE_LOCK_DIR)/board-$(BOARD).lock" ]; then \
                 echo "$(RED)$(BOLD)Board $(BOARD) not locked — run 'make lock-$(BOARD) PHASE=\"description\"' first$(RESET)"; \
@@ -83,7 +92,7 @@ endef
 .PHONY: tokens wallet-setup wallet-info wallet-balance mint-token send-token
 .PHONY: clean erase-nvs reset serial-log bootstrap-config
 .PHONY: cvm-pubkey cvm-test-tool cvm-announce
-.PHONY: lock-a lock-b unlock-a unlock-b force-unlock-a force-unlock-b lock-status
+.PHONY: lock-a lock-b lock-c unlock-a unlock-b unlock-c force-unlock-a force-unlock-b force-unlock-c lock-status
 
 help:
         @echo "TollGate ESP32 — Makefile"
@@ -186,7 +195,7 @@ setup:
 
 flash: build
         @echo "=== Flashing to $(PORT) ==="
-        @echo "$(RED)Error: use 'make flash-a' or 'make flash-b' (per-board lock required)$(RESET)"
+        @echo "$(RED)Error: use 'make flash-a', 'make flash-b', or 'make flash-c' (per-board lock required)$(RESET)"
         @exit 1
 
 flash-a: build
@@ -199,6 +208,11 @@ flash-b: build
         @echo "=== Flashing to $(PORT_B) (Board B) ==="
         . $(IDF_PATH)/export.sh && idf.py -p $(PORT_B) -b $(BAUD) flash
 
+flash-c: build
+        $(call require_lock_c)
+        @echo "=== Flashing to $(PORT_C) (Board C / Display) ==="
+        . $(IDF_PATH)/export.sh && idf.py -p $(PORT_C) -b $(BAUD) flash
+
 build:
         @echo "=== Building $(TARGET) ==="
         . $(IDF_PATH)/export.sh && \
@@ -213,6 +227,10 @@ monitor-b:
         $(call require_lock_b)
         . $(IDF_PATH)/export.sh && idf.py -p $(PORT_B) monitor
 
+monitor-c:
+        $(call require_lock_c)
+        . $(IDF_PATH)/export.sh && idf.py -p $(PORT_C) monitor
+
 # ──────────────────────────────────────────────
 # Testing
 # ──────────────────────────────────────────────
@@ -379,6 +397,9 @@ lock-a: ## Acquire Board A lock (set PHASE="description")
 lock-b: ## Acquire Board B lock (set PHASE="description")
         $(call _acquire_lock,board-b)
 
+lock-c: ## Acquire Board C lock (set PHASE="description")
+        $(call _acquire_lock,board-c)
+
 unlock-a: ## Release Board A lock
         @if [ ! -f "$(HARDWARE_LOCK_DIR)/board-a.lock" ]; then \
                 echo "$(YELLOW)Board A not locked.$(RESET)"; exit 0; \
@@ -393,6 +414,13 @@ unlock-b: ## Release Board B lock
         rm -f $(HARDWARE_LOCK_DIR)/board-b.lock; \
         echo "$(GREEN)Board B lock released.$(RESET)"
 
+unlock-c: ## Release Board C lock
+        @if [ ! -f "$(HARDWARE_LOCK_DIR)/board-c.lock" ]; then \
+                echo "$(YELLOW)Board C not locked.$(RESET)"; exit 0; \
+        fi; \
+        rm -f $(HARDWARE_LOCK_DIR)/board-c.lock; \
+        echo "$(GREEN)Board C lock released.$(RESET)"
+
 force-unlock-a: ## Force-release Board A lock
         @if [ ! -f "$(HARDWARE_LOCK_DIR)/board-a.lock" ]; then \
                 echo "$(YELLOW)Board A not locked.$(RESET)"; exit 0; \
@@ -411,8 +439,17 @@ force-unlock-b: ## Force-release Board B lock
         rm -f $(HARDWARE_LOCK_DIR)/board-b.lock; \
         echo "$(GREEN)Board B force-released.$(RESET)"
 
+force-unlock-c: ## Force-release Board C lock
+        @if [ ! -f "$(HARDWARE_LOCK_DIR)/board-c.lock" ]; then \
+                echo "$(YELLOW)Board C not locked.$(RESET)"; exit 0; \
+        fi; \
+        echo "$(RED)$(BOLD)WARNING: Force-releasing Board C!$(RESET)"; \
+        cat $(HARDWARE_LOCK_DIR)/board-c.lock | sed 's/^/  /'; \
+        rm -f $(HARDWARE_LOCK_DIR)/board-c.lock; \
+        echo "$(GREEN)Board C force-released.$(RESET)"
+
 lock-status: ## Show all board lock statuses
-        @for board in a b; do \
+        @for board in a b c; do \
                 if [ -f "$(HARDWARE_LOCK_DIR)/board-$$board.lock" ]; then \
                         echo "$(YELLOW)Board $$board: LOCKED$(RESET)"; \
                         cat $(HARDWARE_LOCK_DIR)/board-$$board.lock | sed 's/^/  /'; \