Hi,
I am trying to configure my ADS1218 with arduino board. I am using following setting:
AVCC = 5 v
Unipolar
Decimation 1920
Digital filter SINC3
I perform calibration with buffer off and turn it on after calibration.
I am applying 1.3 Vdc on channel Ain0 and Ain1 by setting the MUX to 0x01, fMOD = 9600 hz
Problem is that after calibration I read 0.00 all the time regardless of input which I can vary from 0 to 2 volts.
If I use it without calibration I get 2.5 V all the time regardless of input which I can vary from 0 to 2 volts.
Here is my code:
/**************************************************************
Aalto_ADS1218.ino
this example gives differential voltage across the AN0 And AN1 in uV
Hooking-up with the Arduino
|ADS1218 pin label| Pin Function |Arduino Connection|
|-----------------|:--------------------:|-----------------:|
| DRDY | Data ready Output pin| D6 |
| MISO | Slave Out | D12 |
| MOSI | Slave In | D11 |
| SCLK | Serial Clock | D13 |
| CS | Chip Select | D7 |
| DVDD | Digital VDD | +5V |
| DGND | Digital Gnd | Gnd |
| AN0-AN3 | Analog Input | Analog Input |
| AVDD | Analog VDD | - |
| AGND | Analog Gnd | - |
*************************************************************/
#include <SPI.h>
#define SPI_MASTER_DUMMY 0xff
#define RESET 0x06 //Send the RESET command (06h) to make sure the ADS1220 is properly reset after power-up
#define START 0x08 //Send the START/SYNC command (08h) to start converting in continuous conversion mode
// define the ads1218 command
#define RDATA 0x01 // read the latest ad conversion data
#define RDATAC 0x03 // continuously read the converted data
#define STOPC 0x0F // Stop continuous read mode
#define RREG 0x10 // Two-byte command to read register contents First byte: bit3-bit0 = 0-16;
#define RRAM 0x20 // two-byte command to read the contents of the first byte ram: bit3-bit0 = 0-16;
#define CREG 0x40 // copy the contents of the register to the specified ram bank, the lower three bits specify the ram page address
#define CREGA 0x48 // copy the contents of the register into all ram banks.
#define WREG 0x50 // 2 byte command, write data to register 0-15
#define WRAM 0x60 // 2 bytes instruction, write data to 128 bytes in ram
#define RF2R 0x80 // read the data of the specified FLASH page into 128 bytes of RAM
#define WR2F 0xA0 // Write the data in ram to the specified FLASH page
#define CRAM 0xC0 // Copy the selected ram data into the configuration register, which will overwrite the current working register contents
#define CSRAMX 0xD0 // Calculate the checksum in the specified page ram, do not include ID, DRDY DIO
#define CSARAMX 0xD8 // Calculate the checksum in all rams, do not include ID, DRDY DIO
#define CSREG 0xDF // Calculate the checksum of the configuration register
#define CSRAM 0xE0 // Calculates the checksum in the specified page ram, containing all bits
#define CSARAM 0xE8 // Calculates the checksum in all rams, containing all bits
#define CSFL 0xEC // Calculate the checksum in all FLASH, including all bits
#define SELFCAL 0xF0 // Offset and gain self-calibration
#define SELFOCAL 0xF1 // offset self-calibration
#define SELFGCAL 0xF2 // gain self-calibration
#define SYSOCAL 0xF3 // System Offset Calibration
#define SYSGCAL 0xF4 // System Gain Calibration
#define DSYNC 0xFC // Sync DRDY
#define SLEEP 0xFD // sleep mode
#define RESET 0xFE // reset the register to the power of the data, stop the continuous read mode, does not affect the ram data
// define the ads1218 register Addresses
#define SETUP_REG_ADRS 0x00
#define MUX_REG_ADRS 0x01
#define ACR_REG_ADRS 0x02
#define IDAC1_REG_ADRS 0x03
#define IDAC2_REG_ADRS 0x04
#define ODAC_REG_ADRS 0x05
#define DIO_REG_ADRS 0x06
#define DIR_REG_ADRS 0x07
#define DEC0_REG_ADRS 0x08
#define DEC1_REG_ADRS 0x09
#define OCR0_REG_ADRS 0x0A
#define OCR1_REG_ADRS 0x0B
#define OCR2_REG_ADRS 0x0C
#define FSR0_REG_ADRS 0x0D
#define FSR1_REG_ADRS 0x0E
#define FSR2_REG_ADRS 0x0F
#define ADS1218_CS_PIN 7
#define ADS1218_DRDY_PIN 6
void writeRegister(uint8_t address, uint8_t value)
{
uint8_t numReg = 0x01;
noInterrupts();
digitalWrite(ADS1218_CS_PIN, LOW);
// delayMicroseconds(500);
SPI.transfer(WREG | address);
SPI.transfer(numReg);
SPI.transfer(value);
// delayMicroseconds(500);
digitalWrite(ADS1218_CS_PIN, HIGH);
interrupts();
}
uint8_t readRegister(uint8_t address)
{
uint8_t data;
uint8_t numReg = 0x01;
noInterrupts();
digitalWrite(ADS1218_CS_PIN, LOW);
// delayMicroseconds(500);
SPI.transfer(RREG | address);
SPI.transfer(numReg);
delayMicroseconds(20); // delay of 10 uS needed
data = SPI.transfer(SPI_MASTER_DUMMY);
// delayMicroseconds(500);
digitalWrite(ADS1218_CS_PIN, HIGH);
interrupts();
return data;
}
void printAllreg(void)
{
int read_data0;
for (int i = 0; i <= 15; i++) {
read_data0 = readRegister(i);
Serial.println(read_data0, HEX);
delay(10);
}
}
void SendSELFCALCommand(void)
{
noInterrupts();
digitalWrite(ADS1218_CS_PIN, LOW);
delayMicroseconds(500);
SPI.transfer(SELFCAL);
delayMicroseconds(500);
digitalWrite(ADS1218_CS_PIN, HIGH);
interrupts();
delay(2000);
}
void syncSerialData(void)
{
noInterrupts();
digitalWrite(ADS1218_CS_PIN, LOW);
delayMicroseconds(500);
SPI.transfer(DSYNC);
delayMicroseconds(500);
digitalWrite(ADS1218_CS_PIN, HIGH);
interrupts();
delay(2000);
}
void waitForDataReady(int timeOut) //wait for data ready
{
// wait for /DRDY = 1
while ((digitalRead(ADS1218_DRDY_PIN)) != LOW);
// wait for /DRDY = 0
while ((digitalRead(ADS1218_DRDY_PIN)) == LOW);
}
uint32_t Read_Data(int passFlag)
{
uint32_t dataBits = 0x0000;
if (passFlag)
{
waitForDataReady(0);
noInterrupts();
digitalWrite(ADS1218_CS_PIN, LOW); //Take CS low
// delayMicroseconds(500);
SPI.transfer(RDATA);
delayMicroseconds(20);
byte msbData = SPI.transfer(SPI_MASTER_DUMMY);
byte midData = SPI.transfer(SPI_MASTER_DUMMY);
byte lsbData = SPI.transfer(SPI_MASTER_DUMMY);
// delayMicroseconds(500);
digitalWrite(ADS1218_CS_PIN, HIGH); // Clear CS to high
interrupts();
dataBits = msbData;
dataBits = (dataBits << 8) | midData;
dataBits = (dataBits << 8) | lsbData;
}
return dataBits;
}
void setup()
{
digitalWrite(ADS1218_CS_PIN, HIGH);
pinMode(ADS1218_CS_PIN, OUTPUT);
Serial.begin(9600); //115200 57600
SPI.begin(); // wake up the SPI bus.
SPI.setBitOrder(MSBFIRST);
SPI.setDataMode(SPI_MODE1);
SPI.setClockDivider(SPI_CLOCK_DIV64);
writeRegister(0x00, 0xfc); //0000 1100 ,buffer disabled.
delay(50);
writeRegister(0x08, 0x80); // Decimation register 1, DEC0
delay(50);
writeRegister(0x09, 0x77); // Decimation register 2, DEC1, unipolar, SINC3 filter set
delay(50);
printAllreg();
delay(5000);
SendSELFCALCommand();
delay(5000);
writeRegister(0x00, 0xfe); //0000 01110 ,buffer enabled, fMOD = 9600
delay(50);
writeRegister(0x08, 0x80); // Decimation register 1, DEC0
delay(50);
writeRegister(0x09, 0x77); // Decimation register 2, DEC1, unipolar, SINC3 filter set
delay(50);
writeRegister(0x01, 0x01); // set MUX
delay(50);
syncSerialData(); // Sync Data Ready with Serial clock edge
delay(50);
printAllreg();
}
void loop()
{
uint32_t data32 = 0;
data32 = Read_Data(1);
float value = (float(data32) * 2.5 * 1000000) / 16777216;
Serial.print(" 32bit BIN : ");
Serial.println(data32, BIN);
Serial.print(" Value : ");
Serial.println(value, BIN);
delay(50);
}
Here is my schematic:
Any suggestions???
Thanks in advance,
Tanweer
