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// i2c-mcp4725-dac.cpp
//
// Written by Andrew Meyer <ajm@leaflabs.com>
// Modified by Marti Bolivar <mbolivar@leaflabs.com>
//
// Simple program showing how to control an MCP4725 DAC using the
// libmaple I2C interface. There's an MCP4725 breakout board available
// on SparkFun:
//
// http://www.sparkfun.com/products/8736
//
// How to use:
//
// 1. Connect the DAC SDA and SCL pins to I2C2, with a pullup
// resistor (1 KOhm should work) to VCC.
// 2. Load the sketch and connect to SerialUSB.
// 3. Press the button.
//
// The program then makes sure the DAC is connected properly (during
// setup()), then has the DAC output a sawtooth wave (with loop()).
#include <wirish/wirish.h>
#include <libmaple/i2c.h>
#define MCP_ADDR 0x60
#define MCP_WRITE_DAC 0b01000000
#define MCP_WRITE_EEPROM 0b01100000
#define MCP_PD_NORMAL 0b00000000
#define MCP_PD_1K 0b00000010
#define MCP_PD_100K 0b00000100
#define MCP_PD_500K 0b00000110
static uint8 write_msg_data[3];
static i2c_msg write_msg;
static uint8 read_msg_data[5];
static i2c_msg read_msg;
/*
* DAC control routines
*/
void mcp_i2c_setup(void) {
write_msg.addr = MCP_ADDR;
write_msg.flags = 0; // write, 7 bit address
write_msg.length = sizeof(write_msg_data);
write_msg.xferred = 0;
write_msg.data = write_msg_data;
read_msg.addr = MCP_ADDR;
read_msg.flags = I2C_MSG_READ;
read_msg.length = sizeof(read_msg_data);
read_msg.xferred = 0;
read_msg.data = read_msg_data;
}
void mcp_write_val(uint16 val) {
write_msg_data[0] = MCP_WRITE_DAC | MCP_PD_NORMAL;
uint16 tmp = val >> 4;
write_msg_data[1] = tmp;
tmp = (val << 4) & 0x00FF;
write_msg_data[2] = tmp;
i2c_master_xfer(I2C2, &write_msg, 1, 0);
}
uint16 mcp_read_val() {
uint16 tmp = 0;
i2c_master_xfer(I2C2, &read_msg, 1, 2);
/* We don't care about the status and EEPROM bytes (0, 3, and 4). */
tmp = (read_msg_data[1] << 4);
tmp += (read_msg_data[2] >> 4);
return tmp;
}
int mcp_test() {
uint16 val;
uint16 test_val = 0x0101;
SerialUSB.println("Testing the MCP4725...");
/* Read the value of the register (should be 0x0800 if factory fresh) */
val = mcp_read_val();
SerialUSB.print("DAC Register = 0x");
SerialUSB.println(val, HEX);
mcp_write_val(test_val);
SerialUSB.print("Wrote 0x");
SerialUSB.print(test_val, HEX);
SerialUSB.println(" to the DAC");
val = mcp_read_val();
SerialUSB.print("DAC Register = 0x");
SerialUSB.println(val, HEX);
if (val != test_val) {
SerialUSB.println("ERROR: MCP4725 not responding correctly");
return 0;
}
SerialUSB.println("MCP4725 seems to be working");
return 1;
}
/*
* setup() and loop()
*/
void setup() {
pinMode(BOARD_BUTTON_PIN, INPUT);
i2c_master_enable(I2C2, 0);
mcp_i2c_setup();
waitForButtonPress();
ASSERT(mcp_test());
SerialUSB.println("Starting sawtooth wave");
}
void loop() {
static uint16 dout = 0;
mcp_write_val(dout);
dout += 50;
if (dout >= 32768) {
dout = 0;
}
}
// -- init() and main() -------------------------------------------------------
__attribute__((constructor)) void premain() {
init();
}
int main(void) {
setup();
while (true) {
loop();
}
return 0;
}
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