adafruit-esp32s3-camera: set up backlight at boot & add solarize

the backlight situation will be revisited with the next board prototype,
but it's good to prove this can be done.

Depends on adafruit/esp32-camera#6 which should
be merged before this.

ports/espressif/boards/adafruit_esp32s3_camera/board.c

@@ -35,6 +35,8 @@
 #include "shared-bindings/board/__init__.h"
 
 #include "esp_log.h"
+#include "esp_err.h"
+#include "driver/i2c.h"
 
 displayio_fourwire_obj_t board_display_obj;
 
@@ -50,7 +52,69 @@ uint8_t display_init_sequence[] = {
     0x29, 0 | DELAY, 5,                // _DISPON
 };
 
+#define I2C_MASTER_SCL_IO           34
+#define I2C_MASTER_SDA_IO           33
+#define I2C_MASTER_NUM              0
+#define I2C_MASTER_FREQ_HZ          400000
+#define I2C_MASTER_TX_BUF_DISABLE   0
+#define I2C_MASTER_RX_BUF_DISABLE   0
+#define I2C_MASTER_TIMEOUT_MS       1000
+#define I2C_WAIT                    40      // Timing (in microseconds) for I2C
+
+#define AW9523_ADDR (0x5B)
+#define AW9523_REG_SOFTRESET (0x7f)
+#define AW9523_REG_OUTPUT0 (0x02)
+#define AW9523_REG_CONFIG0 (0x04)
+#define AW9523_DEFAULT_OUTPUT (0)
+#define AW9523_DEFAULT_CONFIG (0x2)
+
+
+static void io_expander_backlight_init(void) {
+    int i2c_num = I2C_MASTER_NUM;
+    i2c_config_t conf = {
+        .mode = I2C_MODE_MASTER,
+        .sda_io_num = I2C_MASTER_SDA_IO,
+        .scl_io_num = I2C_MASTER_SCL_IO,
+        .sda_pullup_en = GPIO_PULLUP_ENABLE,
+        .scl_pullup_en = GPIO_PULLUP_ENABLE,
+        .master.clk_speed = I2C_MASTER_FREQ_HZ,
+    };
+    i2c_param_config(i2c_num, &conf);
+    i2c_driver_install(i2c_num, conf.mode, I2C_MASTER_RX_BUF_DISABLE, I2C_MASTER_TX_BUF_DISABLE, 0);
+    i2c_cmd_handle_t cmd = i2c_cmd_link_create();
+    i2c_master_start(cmd);
+    i2c_master_write_byte(cmd, AW9523_ADDR << 1 | I2C_MASTER_WRITE, true);
+    i2c_master_write_byte(cmd, AW9523_REG_SOFTRESET, true);
+    i2c_master_write_byte(cmd, 0, true);
+    i2c_master_stop(cmd);
+    i2c_master_cmd_begin(i2c_num, cmd, 1000 / portTICK_RATE_MS);
+    i2c_cmd_link_delete(cmd);
+
+    cmd = i2c_cmd_link_create();
+    i2c_master_start(cmd);
+    i2c_master_write_byte(cmd, AW9523_ADDR << 1 | I2C_MASTER_WRITE, true);
+    i2c_master_write_byte(cmd, AW9523_REG_CONFIG0, true);
+    i2c_master_write_byte(cmd, AW9523_DEFAULT_CONFIG >> 8, true);
+    i2c_master_write_byte(cmd, AW9523_DEFAULT_CONFIG & 0xff, true);
+    i2c_master_stop(cmd);
+    i2c_master_cmd_begin(i2c_num, cmd, 1000 / portTICK_RATE_MS);
+    i2c_cmd_link_delete(cmd);
+
+    cmd = i2c_cmd_link_create();
+    i2c_master_start(cmd);
+    i2c_master_write_byte(cmd, AW9523_ADDR << 1 | I2C_MASTER_WRITE, true);
+    i2c_master_write_byte(cmd, AW9523_REG_OUTPUT0, true);
+    i2c_master_write_byte(cmd, AW9523_DEFAULT_OUTPUT >> 8, true);
+    i2c_master_write_byte(cmd, AW9523_DEFAULT_OUTPUT & 0xff, true);
+    i2c_master_stop(cmd);
+    i2c_master_cmd_begin(i2c_num, cmd, 1000 / portTICK_RATE_MS);
+    i2c_cmd_link_delete(cmd);
+
+    i2c_driver_delete(i2c_num);
+}
+
 void board_init(void) {
+    io_expander_backlight_init();
     busio_spi_obj_t *spi = common_hal_board_create_spi(0);
     displayio_fourwire_obj_t *bus = &allocate_display_bus()->fourwire_bus;
     bus->base.type = &displayio_fourwire_type;