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pbreuil
Joined: 10 Sep 2003
Posts: 2
Location: St-Etienne, France
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| driver AD7705.C is false!! |
 Posted: Fri Jan 27, 2006 4:21 am |
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I have lost a lot of hours with CCS's driver for AD7705 (V 3.227, 2005).
I think there are 2 errors (of course, I verified with Analog device data-sheets).
1: Inversion of the sign of signal DRDY
2: inversion of channel 1 & 2
Here is the corrected driver:
And now my AD7705 is running!
| Code: |
/////////////////////////////////////////////////////////////////////////////
//// AD7705.C ////
//// Driver for analog device AD7705 ////
//// ////
//// adc_init() Call after power up ////
//// ////
//// read_adc_value(channel)Read adc value from the specified channel ////
//// ////
//// adc_disable() Disables the adc conversion ////
/////////////////////////////////////////////////////////////////////////////
//// (C) Copyright 1996,2003 Custom Computer Services ////
//// This source code may only be used by licensed users of the CCS C ////
//// compiler. This source code may only be distributed to other ////
//// licensed users of the CCS C compiler. No other use, reproduction ////
//// or distribution is permitted without written permission. ////
//// Derivative programs created using this software in object code ////
//// form are not restricted in any way. ////
/////////////////////////////////////////////////////////////////////////////
//// Driver routines for the AD7705 chip
//Assuming a 2.4576 crystal ocsillator is used between MCLK IN and MCLK OUT
// corrected P Breuil, Ecole des Mines saint-Etienne France
//connection pins to the PIC
#define ADC_DRDY PIN_B1
#define ADC_DO PIN_B2
#define ADC_DI PIN_B3
#define ADC_RESET PIN_B4
#define ADC_CS PIN_B5
#define ADC_CLK PIN_B6
//Operation modes
#define ADC_NORMAL 0x00
#define ADC_SELF 0x40
#define ADC_ZERO_SCALE 0x80
#define ADC_FULL_SCALE 0xc0
//Gain settings
#define ADC_GAIN_1 0x00
#define ADC_GAIN_2 0x08
#define ADC_GAIN_4 0x10
#define ADC_GAIN_8 0x18
#define ADC_GAIN_16 0x20
#define ADC_GAIN_32 0x28
#define ADC_GAIN_64 0x30
#define ADC_GAIN_128 0x38
//Polar operations
#define ADC_BIPOLAR 0x04
#define ADC_UNIPOLAR 0x00
//update rates
#define ADC_50 0x04
#define ADC_60 0x05
#define ADC_250 0x06
#define ADC_500 0x07
void write_adc_byte(BYTE data)
{
BYTE i;
output_low(ADC_CS);
for(i=1;i<=8;++i) {
output_low(ADC_CLK);
output_bit(ADC_DI, shift_left(&data,1,0));
output_high(ADC_CLK);
}
output_high(ADC_CS);
}
long int read_adc_word()
{
BYTE i;
long data;
output_low(ADC_CS);
for(i=1;i<=16;++i) {
output_low(ADC_CLK);
output_high(ADC_CLK);
shift_left(&data,2,input(ADC_DO));
}
output_high(ADC_CS);
return data;
}
//setup the device paramaters(mode, gainsetting, polar operation and output rate)
void setup_adc_device(int calmode, int gainsetting, int operation, int rate)
{
write_adc_byte( 0x20 );//Communications Register set to write of clock register
write_adc_byte( rate );//Clock Register info here
write_adc_byte( 0x10 );//Communications Register set to write of setup register
write_adc_byte( calmode|gainsetting|operation);//Setup Register info here
}
//initailaization routine
void adc_init()
{
output_low(ADC_RESET);
output_high(ADC_CLK);
output_high(ADC_CS); //Set low to AD7715 chip select low pin
output_high(ADC_RESET); //Set high to AD7715 reset low pin
setup_adc_device(ADC_SELF,ADC_GAIN_1,ADC_BIPOLAR,ADC_50);
delay_ms(3000);
}
//read an adc value from the specified channel
long int read_adc_value(int1 ch)
{
long int value;
// while ( !input(ADC_DRDY) ); False!! must wait a falling slope!
while ( input(ADC_DRDY) );
if(ch)
// write_adc_byte(0x38);//communications register set to read of data
register of channel 1 False!
write_adc_byte(0x39);//communications register set to read of data ch1
else
// write_adc_byte(0x39);//communications register set to read of data register of channel 0 false!
write_adc_byte(0x38);//communications register set to read of data
value=read_adc_word();
// while ( input(ADC_DRDY) ); False again, rising slope!
while ( !input(ADC_DRDY) ); // but this line has no utility!
return value;
}
//disable the a/d conversion
void adc_disable()
{
write_adc_byte( 0x20 );//Communications Register set to write of clock register
write_adc_byte( 0x10 );//Clock Register info here
}
//Convert the value read to volts
float convert_to_volts(long data){
return ((float)data*2.5/0xffff);
} |
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draghi
Guest
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| Posted: Sun Mar 11, 2007 3:57 am |
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I think the following definitions are also wrong (inverted)
//Polar operations
#define ADC_BIPOLAR 0x04
#define ADC_UNIPOLAR 0x00
should be
//Polar operations
#define ADC_BIPOLAR 0x00
#define ADC_UNIPOLAR 0x04
...
BTW, has anybody some code which reads all three channels on a AD7706? |
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championx
Joined: 28 Feb 2006
Posts: 151
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| Posted: Wed May 21, 2014 8:29 pm |
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Hi! I'm using your driver but i can't read from the channel 2. I always get 0.
| Code: |
adc_init();
adc2 = read_adc_value(1);
delay_ms(300);
adc1 = read_adc_value(0);
delay_ms(300);
printf("ADC %010lu %010lu",adc1,adc2 );
delay_ms(1000);
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Any ideas? The 2 channels are configured identically (hardware). |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu May 22, 2014 10:39 am |
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| Quote: | | The 2 channels are configured identically (hardware). |
Post a link to the schematic for your AN7705 board. Show the voltages
that you have connected to pins AN1(+) and AN1(-), and also for
AN2(+) and AN2(-). Hopefully, you have connected stable DC voltages
to these pins for your initial testing.
The schematic should show everything, such as the crystal frequency
for MCLK, and all external component values.
Also, don't post to multiple old threads. It won't help you. |
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championx
Joined: 28 Feb 2006
Posts: 151
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| Posted: Tue May 27, 2014 6:38 am |
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| Besides, when configures the adc it only configures de adc channel 0. So, if you want to use the 2 channels you cant. You need to configure the seccond channel and then you are ready to read it. |
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