Yoji KURODA / AD7490

Analog Devices 16 channels, 1MSPS, 12bit ADC with SPI interface

Analog Devices' AD7490 A/D converter chip is a great choice to increase ADC channels to mbed. I wrote a C++ class library, which allows multiple chips on the same SPI serial bus line.

main.cpp - usage of sequential mode (use 2 ADCs)

#include "mbed.h"
#include "AD7490.h"

DigitalOut myled(LED1);
SPI spi(p11,p12,p13);

int main() {

    // set up SPI interface. 
    // should be set before call AD7490 constructer
    spi.format(16,0);
    spi.frequency(1000000);

    // construct AD7490 instances
    AD7490 ad1(spi, p9);
    AD7490 ad2(spi, p10);

    // start ad conversion with sequential mode
    ad1.sequential();
    ad2.sequential();

    while(1) {
        short ad_data[32];      // user buffer area

        myled = 1;
        ad1.read(&ad_data[ 0]);  // save the first ADC data to buffer
        ad2.read(&ad_data[16]);  // save the second ADC data to buffer
        myled = 0;

        for(int i=0; i<32; i++)
            printf("ch[%2d]: %d\n", i, ad_data[i]);
        puts("");
        
        wait(1);
    }
}

API

AD7490
AD7490(SPI _spi, PinName _cs)Constructor. needs SPI instance and the Chip select pin
unsigned short convert(int ch=0)Single channel (one shot) conversion.
void convert(short data[]);All channels conversion with multiple 'one shot conversion'
unsigned short sequential(int ch=15);Start sequential mode, from channel 0 to 'ch'. ch=15 is default
void read(short buffer[]);Read data channel [0] to [ch], and copy them to user buffer area

AD7490.h

Committer:
ykuroda
Date:
2012-08-29
Revision:
0:95be7403a10c
Child:
1:ac3b7f978aa3

File content as of revision 0:95be7403a10c:

//
//  AD7490
//
#ifndef _AD7490_H
#define _AD7490_H

class AD7490 {
  protected:
    #define CREG_WRITE    0x800
    #define CREG_SEQ      0x400
    #define CREG_ADD3     0x200
    #define CREG_ADD2     0x100
    #define CREG_ADD1     0x080
    #define CREG_ADD0     0x040
    #define CREG_PM1      0x020
    #define CREG_PM0      0x010
    #define CREG_SHADOW   0x008
    #define CREG_WEAK     0x004
    #define CREG_RANGE    0x002
    #define CREG_CODING   0x001

    SPI spi;
    DigitalOut cs;
    short ret;
    
  public:
    AD7490(SPI _spi, PinName _cs);
    ~AD7490();
    unsigned short convert(int ch=0);
    void convert(short data[]);    

    unsigned short sequential(int ch=15);
    unsigned short read(void);
    void read(short data[]);
};


#if 0
int main() {

    wait(1);

    // set up SPI interface
    SPI spi(p11,p12,p13);
    spi.format(16,0);
    spi.frequency(1000000);

    AD7490 ad1(spi, p9);
    AD7490 ad2(spi, p10);

    while(1) {

        int ret=0;
        for(int ch=0; ch<16; ch++){
            ret = ad1.convert(ch);
            printf("ch=%2d, ret= %d, %f\n", (ret>>12)&0xF, ret&0xFFF, 3.3*(float)(ret&0xFFF)/0xFFF);
        }
        printf("\n");
        for(int ch=0; ch<16; ch++){
            ret = ad2.convert(ch);
            printf("ch=%2d, ret= %d, %f\n", (ret>>12)&0xF, ret&0xFFF, 3.3*(float)(ret&0xFFF)/0xFFF);
        }
        printf("\n");

        myled = 1;
        wait(0.1);
        myled = 0;
        wait(0.9);
    }
}
#endif  // test main

#endif  // _AD7490_H