added read write and init (#68)

* added read write and init

* typedefed the function pointers

---------

Co-authored-by: Dylan Donahue <[email protected]>

general/include/mcp23008.h

@@ -0,0 +1,19 @@
+#ifndef MCP23008_H
+#define MCP23008_H 
+
+#include <stdint.h>
+
+typedef int (*write_ptr)(uint8_t addr, const uint8_t *data, uint8_t len);
+typedef int (*read_ptr)(uint8_t addr, uint8_t *data, uint8_t len);
+typedef struct {
+    write_ptr write;
+    read_ptr read;
+} mcp23008_t;
+
+int mcp23008_init(mcp23008_t *obj, write_ptr write, read_ptr read);
+
+int mcp23008_write_reg(mcp23008_t obj, uint8_t reg, uint8_t data);
+int mcp23008_read_reg(mcp23008_t obj, uint8_t reg, uint8_t *data);
+
+#endif // MCP23008_H
+

general/src/mcp23008.c

@@ -0,0 +1,35 @@
+/*
+	MCP23008 GPIO Expander Source File
+	Link to part Datasheet for reference:
+	https://ww1.microchip.com/downloads/en/DeviceDoc/MCP23008-MCP23S08-Data-Sheet-20001919F.pdf
+
+	Author: Dylan Donahue
+*/
+
+#include "mcp23008.h"
+
+#define MCP23008_I2C_ADDR   0x20 
+#define IO_CONFIG_REG 		0x00
+#define IO_CONFIG_OUTPUT 	0x00 /* = 0000 0000, all output */
+#define IO_CONFIG_INPUT 	0xFF /* = 1111 1111, all input */
+#define INPUT_REG 			0x09
+
+int mcp23008_init(mcp23008_t *obj, write_ptr write_func, read_ptr read_func)
+{
+    obj->write = write_func;
+    obj->read = read_func;
+
+    uint8_t buf[2] = {IO_CONFIG_REG, IO_CONFIG_OUTPUT};
+    return obj->write(MCP23008_I2C_ADDR, buf, 2);
+}
+
+int mcp23008_write_reg(mcp23008_t *obj, uint8_t reg, uint8_t val)
+{
+    uint8_t buf[2] = {reg, val};
+    return obj->write(MCP23008_I2C_ADDR, buf, 2);
+}
+
+int mcp23008_read_reg(mcp23008_t *obj, uint8_t reg, uint8_t *val)
+{
+    return obj->read(MCP23008_I2C_ADDR, val, 1);
+}