Diff: mcp342x.cpp

Revision:

0:7dbf7356da6b

Child:

1:c4da9889ff85

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mcp342x.cpp	Wed Jun 15 10:37:24 2016 +0000
@@ -0,0 +1,125 @@
+#include "mcp342x.h"
+
+#define LEN_ONE_BYTE 1
+#define REQUEST_N_BYTES 4
+
+MCP342x::MCP342x(I2C *i2c, uint8_t device_address)
+{
+    // The address byte is the device code (4 bits, hardcoded in
+    // factory) and the device address (3 bits). These are shifted one
+    // bit to the left because mbed uses 8-bit addresses.
+    _address = (_device_code << 4) | (device_address << 1);
+    _i2c = i2c;
+    // Initialise to default settings.
+    set_channel(CHANNEL_1);
+    set_resolution(RESOLUTION_12);
+    set_pga(PGA_1);
+}
+
+void MCP342x::set_channel(mcp342x_channel_t channel)
+{
+    _configuration[0] &= REG_CHANNEL_Clear;
+    _configuration[0] |= channel << REG_CHANNEL_Pos;
+    _write_configuration();
+}
+
+void MCP342x::set_conversion_mode(mcp342x_conversion_mode_t mode)
+{
+    _configuration[0] &= REG_MODE_Clear;
+    _configuration[0] |= mode << REG_MODE_Pos;
+    _write_configuration();
+}
+
+void MCP342x::set_resolution(mcp342x_resolution_t resolution)
+{
+    switch(resolution) {
+        case RESOLUTION_12:
+            _resolution = 12;
+            break;
+        case RESOLUTION_14:
+            _resolution = 14;
+            break;
+        case RESOLUTION_16:
+            _resolution = 16;
+            break;
+        case RESOLUTION_18:
+            _resolution = 18;
+            break;
+        }
+    _configuration[0] &= REG_RESOLUTION_Clear;
+    _configuration[0] |= resolution << REG_RESOLUTION_Pos;
+    _write_configuration();
+}
+
+void MCP342x::set_pga(mcp342x_pga_t pga)
+{
+    switch(pga) {
+        case PGA_1:
+            _pga = 1;
+            break;
+        case PGA_2:
+            _pga = 2;
+            break;
+        case PGA_4:
+            _pga = 4;
+            break;
+        case PGA_8:
+            _pga = 8;
+            break;
+        }
+    _configuration[0] &= REG_PGA_Clear;
+    _configuration[0] |= pga << REG_PGA_Pos;
+    _write_configuration();
+}
+
+void MCP342x::_write_configuration()
+{
+    _i2c->write(_address, _configuration, LEN_ONE_BYTE);
+}
+
+float MCP342x::read_volts(){
+    long adc_value = read();
+    float volts = 0.0;
+    float lsb = 2 * 2.048 / 2^_resolution;
+    int max_code = 2^(_resolution-1) - 1;
+
+    if (adc_value > max_code) {
+        volts = (~adc_value & max_code) + 1;
+        volts *= -1;
+    } else {
+        volts = (float)adc_value;
+    }
+
+    return volts * lsb/(float)_pga;
+}
+
+long MCP342x::read()
+{
+    char raw_data[REQUEST_N_BYTES];
+    long adc_value = 0;
+
+    _i2c->read(_address, raw_data, REQUEST_N_BYTES);
+
+    switch (_resolution) {
+        case 12:
+            adc_value = (raw_data[1] << 8) | raw_data[0];
+            adc_value &= 0xfff;
+            break;
+
+        case 14:
+            adc_value = (raw_data[1] << 8) | raw_data[0];
+            adc_value &= 0x3fff;
+            break;
+
+        case 16:
+            adc_value = (raw_data[1] << 8) | raw_data[0];
+            adc_value &= 0xffff;
+            break;
+
+        case 18:
+            adc_value = (raw_data[2] << 16) | (raw_data[1] << 8) | raw_data[0];
+            adc_value &= 0x3ffff;
+            break;
+    }
+    return adc_value;
+}