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.cpp

Revision:
1:ac3b7f978aa3
Parent:
0:95be7403a10c
Child:
2:a547c48d2152
--- a/AD7490.cpp	Wed Aug 29 11:01:51 2012 +0000
+++ b/AD7490.cpp	Wed Aug 29 14:10:30 2012 +0000
@@ -5,7 +5,7 @@
 :   spi(_spi),
     cs(_cs)
 {
-    short x = 0;
+    unsigned short x = 0;
 
     for(int i=0; i<3; i++){
  
@@ -23,7 +23,7 @@
         x |= CREG_CODING;
      
         cs = 0;
-        ret = spi.write(x<<4);
+        unsigned short ret = spi.write(x<<4);
         cs = 1;
     
 //        printf("INIT: send = 0x%X, ret = 0x%X\n", x, ret);
@@ -53,7 +53,7 @@
     x |= CREG_CODING;
 
     cs = 0;
-    ret = spi.write(x<<4);
+    unsigned short ret = spi.write(x<<4);
     cs = 1;
 
 //    printf("send = 0x%X, ch = %2d, ret = %d\n", x, (ret>>12)&0xF, ret&0xFFF);
@@ -92,7 +92,7 @@
     x |= CREG_CODING;
 
     cs = 0;
-    ret = spi.write(x<<4);
+    unsigned short ret = spi.write(x<<4);
     cs = 1;
 
     return ret;
@@ -119,7 +119,7 @@
 //    x |= CREG_CODING;
 
     cs = 0;
-    ret = spi.write(x<<4);
+    unsigned short ret = spi.write(x<<4);
     cs = 1;
 
 //    printf("send = 0x%X, ch = %2d, ret = %d\n", x, (ret>>12)&0xF, ret&0xFFF);
@@ -137,43 +137,3 @@
         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