Add a demo code for PicoCalc

Code/picocalc_helloworld/i2ckbd/i2ckbd.h

@@ -0,0 +1,19 @@
+#ifndef I2C_KEYBOARD_H
+#define I2C_KEYBOARD_H
+#include <pico/stdlib.h>
+#include <pico/platform.h>
+#include <hardware/gpio.h>
+#include <hardware/i2c.h>
+
+#define I2C_KBD_MOD i2c1
+#define I2C_KBD_SDA 6
+#define I2C_KBD_SCL 7
+
+#define I2C_KBD_SPEED  400000 // if dual i2c, then the speed of keyboard i2c should be 10khz
+
+#define I2C_KBD_ADDR 0x1F
+
+void init_i2c_kbd();
+int read_i2c_kbd();
+
+#endif