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

Diff: AD7490.h

Revision:
3:b7e72acaade2
Parent:
2:a547c48d2152
Child:
4:f059fdd25051
--- a/AD7490.h	Wed Aug 29 14:19:06 2012 +0000
+++ b/AD7490.h	Mon Sep 24 21:33:14 2012 +0000
@@ -25,16 +25,17 @@
     
     SPI spi;
     DigitalOut cs;
+
+    unsigned short read(void);  // dummy read for triggering at sequential mode
     
   public:
     AD7490(SPI _spi, PinName _cs);
     ~AD7490();
-    unsigned short convert(int ch=0);
-    void convert(short data[]);    
+    unsigned short convert(int ch=0);       // one shot conversion at channel [ch]
+    void convert(short data[]);             // convert all (16) channels with one short conv.
 
-    unsigned short sequential(int ch=15);
-    unsigned short read(void);
-    void read(short data[]);
+    unsigned short sequential(int ch=15);   // start sequential mode from channel [0] to [ch]
+    void read(short data[]);                // read [0] to [ch], and copy to user area
 };
 
 #endif  // _AD7490_H
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