Diff: mcp342x.h

Revision:

0:7dbf7356da6b

Child:

1:c4da9889ff85

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mcp342x.h	Wed Jun 15 10:37:24 2016 +0000
@@ -0,0 +1,195 @@
+/**
+ * Author: Antonio Gonzalez <antgon@cantab.net>
+ * Copyright (c) 2016 The Francis Crick Institute.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef MCP342x_h
+#define MCP342x_h
+
+#include "mbed.h"
+
+/**
+ * @brief Microchip analog-to-digital converter MCP3422/3/4
+ *
+ * Library for using Microchip's family of analog-to-digital converters
+ * MCP3422/3/4. Some features of these include:
+ * - 12-, 14-, 16-, or 18-bit ADC.
+ * - Two-wire I2C interface.
+ * - Sampling rate, 3.75 (18-bit), 15 (16-bit), 60 (14-bit), or 240
+ *   (12-bit) SPS.
+ * - Two (MCP3422/3) or four (MCP3424) channels, differential input.
+ * - Internal voltage reference, 2.048 V.
+ * - Selectable PGA, x1, x2, x4, or x8.
+ * - Conversion modes: one-shot or continuous.
+ *
+ * TODO:
+ * - Implement 'conversion mode one-shot'
+ *
+ * Example:
+ * @code
+ * #include "mbed.h"
+ * #include "mcp342x.h"
+ *
+ * I2C i2c(p9, p10);
+ * MCP342x mcp_adc(&i2c);
+ *
+ * int main(){
+ *     mcp_adc.set_channel(MCP342x::CHANNEL_2);
+ *     mcp_adc.set_pga(MCP342x::PGA_4);
+ *     mcp_adc.set_resolution(MCP342x::RESOLUTION_12);
+ *
+ *     while(1){
+ *         // Channel 2 was selected above. Read data from this channel.
+ *         long chan2_val = mcp_adc.read();
+ *
+ *         // Select now channel 1 and read it.
+ *         mcp_adc.set_channel(MCP342x::CHANNEL_1);
+ *         long chan1_val = mcp_adc.read();
+ *
+ *         printf("CH1 %i  CH2 %i\r\n", chan1_val, chan2_val);
+ *         wait(5);
+ *     }
+ * }
+ * @endcode
+ */
+class MCP342x
+{
+public:
+    // Registers.
+    // The device has only one register, which is the configuration
+    // byte. It consists of these bits:
+    //   7    ~ready
+    //   6-5  channel selection
+    //   4    conversion mode (one-shot, continuous)
+    //   3-2  sample rate selection (12, 14, 16, or 18)
+    //   1-0  PGA gain selection (1x, 2x, 4x, or 8x)
+    typedef enum {
+        REG_PGA_Pos = 0,
+        REG_RESOLUTION_Pos = 2,
+        REG_MODE_Pos = 4,
+        REG_CHANNEL_Pos = 5,
+        REG_RDY_Pos = 7,
+
+        REG_PGA_Clear = ~(0x3 << REG_PGA_Pos),
+        REG_RESOLUTION_Clear = ~(0x3 << REG_RESOLUTION_Pos),
+        REG_MODE_Clear = ~(0x1 << REG_MODE_Pos),
+        REG_CHANNEL_Clear = ~(0x3 << REG_CHANNEL_Pos),
+        REG_RDY_Clear = ~(0x1 << REG_RDY_Pos)
+    } mcp342x_reg_t;
+
+    // Programmable gain.
+    typedef enum {
+        PGA_1 = 0,
+        PGA_2 = 1,
+        PGA_4 = 2,
+        PGA_8 = 3
+    } mcp342x_pga_t;
+
+    // Resolution.
+    typedef enum {
+        RESOLUTION_12 = 0,
+        RESOLUTION_14 = 1,
+        RESOLUTION_16 = 2,
+        RESOLUTION_18 = 3
+    } mcp342x_resolution_t;
+
+    // Conversion mode.
+    typedef enum {
+        CONVERSION_MODE_ONESHOT = 0,
+        CONVERSION_MODE_CONTINUOUS = 1
+    } mcp342x_conversion_mode_t;
+
+    // Channels.
+    typedef enum {
+        CHANNEL_1 = 0,
+        CHANNEL_2 = 1,
+        CHANNEL_3 = 2,
+        CHANNEL_4 = 3
+    } mcp342x_channel_t;
+
+    /**
+    * MCP342x constructor
+    *
+    * @param i2c Pointer to I2C
+    * @param device_address Address for this sensor
+    */
+    MCP342x(I2C *i2c, uint8_t device_address = 0b000);
+
+    /**
+    * Set channel to read from.
+    *
+    * @param channel Channel number
+    */
+    void set_channel(mcp342x_channel_t channel);
+
+    /**
+    * Set conversion mode.
+    *
+    * @param mode Conversion mode. Options are
+    * MCP342x::CONVERSION_MODE_ONESHOT or
+    * MCP342x::CONVERSION_MODE_CONTINUOUS.
+    */
+    void set_conversion_mode(mcp342x_conversion_mode_t mode);
+
+    /**
+    * Set resolution.
+    *
+    * @param resolution Resolution, one of
+    * MCP342x::RESOLUTION_12, MCP342x::RESOLUTION_14,
+    * MCP342x::RESOLUTION_16 or MCP342x::RESOLUTION_18.
+    */
+    void set_resolution(mcp342x_resolution_t resolution);
+
+    /**
+    * Set programable gain amplifier. Options are
+    * MCP342x::PGA_1, MCP342x::PGA_2, MCP342x::PGA_4, or MCP342x::PGA_8.
+    */
+    void set_pga(mcp342x_pga_t pga);
+
+    /**
+    * Read the ADC value. The value will be that read from the channel
+    * set previously (`set_channel`)
+    *
+    * @return Analog measurement in raw data (integer)
+    */
+    long read();
+
+    /**
+    * Read the ADC value in volts. The value will be that read from the
+    * channel set previously (`set_channel`).
+    *
+    * The data are coded in two's complements format, and the final
+    * voltage is also a function of the resolution and gain settings.
+    * This function follows the equations presented in the device's
+    * datasheet (Microchip DS22088C), Section 4.9.
+    *
+    * @return Analog measurement in volts (float)
+    */
+    float read_volts();
+
+private:
+    uint8_t _address;
+    I2C *_i2c;
+    uint8_t _resolution;
+    uint8_t _pga;
+    char _configuration[1];
+    static const uint8_t _device_code = 0b1101; // Hardcoded in factory
+    void _write_configuration();
+};
+
+//void mcp342x_start_conversion(void); For one-shot mode.
+
+#endif