MicroPython: Port wakeup GPIO latch to asm.

micropython/modules/wakeup/micropython.cmake

@@ -5,6 +5,7 @@ add_library(usermod_${MOD_NAME} INTERFACE)
 target_sources(usermod_${MOD_NAME} INTERFACE
     ${CMAKE_CURRENT_LIST_DIR}/${MOD_NAME}.c
     ${CMAKE_CURRENT_LIST_DIR}/${MOD_NAME}.cpp
+    ${CMAKE_CURRENT_LIST_DIR}/${MOD_NAME}.S
 )
 
 target_include_directories(usermod_${MOD_NAME} INTERFACE

micropython/modules/wakeup/wakeup.S

@@ -0,0 +1,26 @@
+
+.syntax unified
+.cpu cortex-m0plus
+.thumb
+
+#include "pico/asm_helper.S"
+
+// This macro tells the pico runtime to call __wakeup_gpio_latch very early in boot
+__pre_init __wakeup_gpio_latch, 00001
+
+.section .data.wakeup_gpio_latch
+.global wakeup_gpio_state
+.align 4
+wakeup_gpio_state:
+.word 0x00000000
+
+.section .text
+.thumb_func
+__wakeup_gpio_latch:
+   // Read GPIO state for front buttons and store
+   movs r3, 0xd0                // Load 0xd0 into r3
+   lsls r3, r3, 24              // Shift left 24 to get 0xd0000000
+   ldr r1, [r3, 4]              // Load GPIO state (0xd0000004) into r1
+   ldr r2, =wakeup_gpio_state   // Load output var addr into r2
+   str r1, [r2]                 // Store r1 to r2
+   bx lr                        // Return

micropython/modules/wakeup/wakeup.cpp

@@ -12,19 +12,16 @@
 #define WAKEUP_PIN_VALUE ((0b1 << 2) | (0b1 << 6))
 #endif
 
+extern uint32_t wakeup_gpio_state;
+
 namespace {
     struct Wakeup {
         public:
-            uint32_t wakeup_gpio_state;
-
             Wakeup() {
                 // Assert wakeup pins (indicator LEDs, VSYS hold etc)
                 gpio_init_mask(WAKEUP_PIN_MASK);
                 gpio_set_dir_masked(WAKEUP_PIN_MASK, WAKEUP_PIN_DIR);
                 gpio_put_masked(WAKEUP_PIN_MASK, WAKEUP_PIN_VALUE);
-
-                // Latch GPIO state into variable
-                Wakeup::wakeup_gpio_state = gpio_get_all();
             }
     };
 
@@ -35,7 +32,7 @@ extern "C" {
 #include "wakeup.h"
 
 mp_obj_t Wakeup_get_gpio_state() {
-    return mp_obj_new_int(wakeup.wakeup_gpio_state);
+    return mp_obj_new_int(wakeup_gpio_state);
 }
 
 }