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