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

Files at this revision

API Documentation at this revision

Revision 0:95be7403a10c, committed 2012-08-29

Comitter:
ykuroda
Date:
Wed Aug 29 11:01:51 2012 +0000
Child:
1:ac3b7f978aa3
Commit message:
Analog Devices AD7490 16 channels, 1MSPS, 12Bit ADC with SPI interface

Changed in this revision

AD7490.cpp Show annotated file Show diff for this revision Revisions of this file
AD7490.h Show annotated file Show diff for this revision Revisions of this file 
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/AD7490.cpp	Wed Aug 29 11:01:51 2012 +0000
@@ -0,0 +1,179 @@
+#include "mbed.h"
+#include "AD7490.h"
+
+AD7490::AD7490(SPI _spi, PinName _cs)
+:   spi(_spi),
+    cs(_cs)
+{
+    short x = 0;
+
+    for(int i=0; i<3; i++){
+ 
+        x = 0;    
+        x |= CREG_WRITE;
+    //    x |= CREG_SEQ;
+    //    x |= CREG_SHADOW;
+        x |= CREG_ADD3;
+        x |= CREG_ADD2;
+        x |= CREG_ADD1;
+        x |= CREG_ADD0;
+        x |= CREG_PM1;
+        x |= CREG_PM0;
+        x |= CREG_RANGE;
+        x |= CREG_CODING;
+     
+        cs = 0;
+        ret = spi.write(x<<4);
+        cs = 1;
+    
+//        printf("INIT: send = 0x%X, ret = 0x%X\n", x, ret);
+    }
+}
+
+AD7490::~AD7490()
+{
+}
+
+unsigned short
+AD7490::convert(int ch)
+{
+    unsigned short x = 0;
+
+    x |= CREG_WRITE;
+//    x |= CREG_SEQ;
+//    x |= CREG_SHADOW;
+//    x |= CREG_ADD3;
+//    x |= CREG_ADD2;
+//    x |= CREG_ADD1;
+    x |= (CREG_ADD0|CREG_ADD1|CREG_ADD2|CREG_ADD3) & (ch<<6);
+
+    x |= CREG_PM1;
+    x |= CREG_PM0;
+    x |= CREG_RANGE;
+    x |= CREG_CODING;
+
+    cs = 0;
+    ret = spi.write(x<<4);
+    cs = 1;
+
+//    printf("send = 0x%X, ch = %2d, ret = %d\n", x, (ret>>12)&0xF, ret&0xFFF);
+
+    return ret;
+}
+
+void
+AD7490::convert(short data[])
+{
+    for(int ch=0; ch<16; ch++) data[ch]=0;
+    for(int ch=0; ch<16; ch++){
+        unsigned short ret = convert(ch);
+
+        data[ ret>>12&0xF ] = ret&0xFFF;
+    }
+}
+
+
+unsigned short
+AD7490::sequential(int ch)
+{
+    unsigned short x = 0;
+
+    x |= CREG_WRITE;
+    x |= CREG_SEQ;
+    x |= CREG_SHADOW;
+//    x |= CREG_ADD3;
+//    x |= CREG_ADD2;
+//    x |= CREG_ADD1;
+    x |= (CREG_ADD0|CREG_ADD1|CREG_ADD2|CREG_ADD3) & (ch<<6);
+
+    x |= CREG_PM1;
+    x |= CREG_PM0;
+    x |= CREG_RANGE;
+    x |= CREG_CODING;
+
+    cs = 0;
+    ret = spi.write(x<<4);
+    cs = 1;
+
+    return ret;
+}
+
+
+
+unsigned short
+AD7490::read(void)
+{
+    unsigned short x = 0;
+
+//    x |= CREG_WRITE;
+//    x |= CREG_SEQ;
+//    x |= CREG_SHADOW;
+//    x |= CREG_ADD3;
+//    x |= CREG_ADD2;
+//    x |= CREG_ADD1;
+//    x |= (CREG_ADD0|CREG_ADD1|CREG_ADD2|CREG_ADD3) & (ch<<6);
+
+//    x |= CREG_PM1;
+//    x |= CREG_PM0;
+//    x |= CREG_RANGE;
+//    x |= CREG_CODING;
+
+    cs = 0;
+    ret = spi.write(x<<4);
+    cs = 1;
+
+//    printf("send = 0x%X, ch = %2d, ret = %d\n", x, (ret>>12)&0xF, ret&0xFFF);
+
+    return ret;
+}
+
+void
+AD7490::read(short data[])
+{
+    for(int ch=0; ch<16; ch++) data[ch]=0;
+    for(int ch=0; ch<16; ch++){
+        unsigned short ret = read();
+
+        data[ ret>>12&0xF ] = ret&0xFFF;
+    }
+}
+
+
+
+
+
+
+#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

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/AD7490.h	Wed Aug 29 11:01:51 2012 +0000
@@ -0,0 +1,73 @@
+//
+//  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