Add a demo code for PicoCalc

Code/picocalc_helloworld/i2ckbd/i2ckbd.c

@@ -0,0 +1,57 @@
+#include <stdio.h>
+#include <pico/stdio.h>
+#include "i2ckbd.h"
+
+static uint8_t i2c_inited = 0;
+
+void init_i2c_kbd() {
+    gpio_set_function(I2C_KBD_SCL, GPIO_FUNC_I2C);
+    gpio_set_function(I2C_KBD_SDA, GPIO_FUNC_I2C);
+    i2c_init(I2C_KBD_MOD, I2C_KBD_SPEED);
+    gpio_pull_up(I2C_KBD_SCL);
+    gpio_pull_up(I2C_KBD_SDA);
+
+    i2c_inited = 1;
+}
+
+int read_i2c_kbd() {
+    int retval;
+    static int ctrlheld = 0;
+    uint16_t buff = 0;
+    unsigned char msg[2];
+    int c = -1;
+    msg[0] = 0x09;
+
+    if (i2c_inited == 0) return -1;
+
+    retval = i2c_write_timeout_us(I2C_KBD_MOD, I2C_KBD_ADDR, msg, 1, false, 500000);
+    if (retval == PICO_ERROR_GENERIC || retval == PICO_ERROR_TIMEOUT) {
+        printf("i2c write error\n");
+        return -1;
+    }
+
+    retval = i2c_read_timeout_us(I2C_KBD_MOD, I2C_KBD_ADDR, (unsigned char *) &buff, 2, false, 500000);
+    if (retval == PICO_ERROR_GENERIC || retval == PICO_ERROR_TIMEOUT) {
+        printf("i2c read error read\n");
+        return -1;
+    }
+
+    if (buff != 0) {
+        if (buff == 0x7e03)ctrlheld = 0;
+        else if (buff == 0x7e02) {
+            ctrlheld = 1;
+        } else if ((buff & 0xff) == 1) {//pressed
+            c = buff >> 8;
+            int realc = -1;
+            switch (c) {
+                default:
+                    realc = c;
+                    break;
+            }
+            c = realc;
+            if (c >= 'a' && c <= 'z' && ctrlheld)c = c - 'a' + 1;
+        }
+        return c;
+    }
+    return -1;
+}