Add i2c slave support to arduino firmware

src/board/arduino/mega2560/battery.c

@@ -6,6 +6,10 @@ uint8_t smbus_read(uint8_t address, uint8_t command, uint16_t * data) {
     return i2c_get(address, command, (uint8_t *)data, 2);
 }
 
+uint8_t smbus_write(uint8_t address, uint8_t command, uint16_t data) {
+    return i2c_set(address, command, (uint8_t *)&data, 2);
+}
+
 void battery_debug(void) {
     uint16_t data = 0;
     uint8_t err = 0;
@@ -15,9 +19,9 @@ void battery_debug(void) {
         err = smbus_read(A, V, &data); \
         if (err) { \
             printf("ERROR %02X\n", err); \
-            return; \
+        } else { \
+            printf("%04X\n", data); \
         } \
-        printf("%04X\n", data); \
     }
 
     printf("Battery:\n");

src/board/arduino/mega2560/include/board/i2c.h

@@ -1,6 +1,8 @@
 #ifndef _BOARD_I2C_H
 #define _BOARD_I2C_H
 
+#include <arch/i2c.h>
+
 void i2c_init(unsigned long baud);
 
 #endif // _BOARD_I2C_H

src/board/arduino/mega2560/main.c

@@ -1,6 +1,7 @@
 #include <stdio.h>
 
 #include <arch/gpio.h>
+#include <arch/i2c_slave.h>
 #include <arch/uart.h>
 #include <board/battery.h>
 #include <board/i2c.h>
@@ -10,6 +11,16 @@ void init(void) {
     i2c_init(50000);
 }
 
+static void i2c_slave_new() {}
+
+static void i2c_slave_recv(uint8_t data) {
+    printf("%c", data);
+}
+
+static uint8_t i2c_slave_send() {
+    return 0;
+}
+
 struct Gpio LED = GPIO(B, 7);
 
 int main(void) {
@@ -22,7 +33,9 @@ int main(void) {
     battery_debug();
 
     for (;;) {
+        i2c_slave_init(0x76, i2c_slave_new, i2c_slave_recv, i2c_slave_send);
         int c = getchar();
+        i2c_slave_stop();
         if (c == '\r') {
             putchar('\n');
             battery_debug();