ADS1255: How to simply code ADS1255 with Arduino

Hi Yang,

One more thought, regarding the "Serial.println(adc_val*PGAmulti_1,10);" statement...

In many cases, you would need to convert the number to a string before you can print the value. A formatted print function might allow you to do this with a format specifier, for example: printf("Voltage = %d\r\n", (double) adc_val*PGAmulti_1);

Best Regards,
Chris

Hi Christopher

I followed your advice. And I changed my code a little bit.

For example: I added the delay 7 microseconds

//----------- For part of setup 

Serial.println("Status Data setup started");

 byte status_data = 0x01; //status: Most Significant Bit First, Auto-Calibration Disabled, Analog Input Buffer Disabled

 SPI.transfer(0x50 | status_reg);

 SPI.transfer(0x00);   // 2nd command byte, write one register only

 delayMicroseconds(7);                                             ---------------------- ------------------------------ADD t6 correct position?

 SPI.transfer(status_data);   // write the databyte to the register

 delayMicroseconds(10);                                            ------------------------------should I delay??

 //-----------------------------------------------

 //-------------------------------

 // ADCON setup

 //byte adcon_data = 0x00; // 0 00 00 000

 Serial.println("ADCON Data setup started");

 SPI.transfer(0x50 | ADCON);

 SPI.transfer(0x00);   // 2nd command byte, write one register only

 delayMicroseconds(7);                                               ---------------------- ------------------------------ADD t6 correct position?

 SPI.transfer(PGA_1);   // write the databyte to the register

 Serial.println("ADCON Data setup ended");

 delayMicroseconds(10);                                             --------------------------------------------------------------should I delay??

//-------------------

And for main loop:

void AIN_0_COM()

{

 long adc_val =0; // store reading

 digitalWrite(cs, LOW);

 SPI.beginTransaction(SPISettings(SPISPEED, MSBFIRST, SPI_MODE1)); // start SPI

 delayMicroseconds(10);

 while (digitalRead(rdy)) {} ;

 SPI.transfer(SDATAC);                                             ---------------------------------add SDATAC to make sure  in SDATAC model

                                                                                                 ------------------------------should I delay??

 //byte channel = 0;

 //byte data = (channel << 4) | (1 << 3); //AIN-channel and AINCOM

 //byte data = 1;

 SPI.transfer(0x50 | 1); // MUX register (0101 rrrr)

 SPI.transfer(0x00);   // 2nd command byte, write one register only

 //SPI.transfer(AIN0_COM);   // write the databyte to the register

 delayMicroseconds(7);//t6                                                ------------------------------ADD t6

 SPI.transfer(P_AIN0 + N_AINCOM);

 delayMicroseconds(10);                                                         ---------Should I delay here??

 //SYNC command 1111 1100

 SPI.transfer(SYNC);

 delayMicroseconds(10);                                                        ---------Should I delay here??/

 //WAKEUP 0000 0000

 SPI.transfer(WAKEUP);

 delayMicroseconds(34);                                                     --------------------add one shot delay here

 SPI.transfer(0x01); // Read Data 0000  0001 (01h)

 //delayMicroseconds(10);                                                       ---------Should I delay here??/

 adc_val = SPI.transfer(0);

 adc_val <<= 8; //shift to left

 adc_val |= SPI.transfer(0);

 adc_val <<= 8;

 adc_val |= SPI.transfer(0);

 while (digitalRead(rdy) == HIGH) {} ;                                 ADD to detect if Dready go high to finish one shot

 delayMicroseconds(3);//t 17                                                ADD T17 wait for one shot I used 7.86M

 digitalWrite(cs, HIGH);

 SPI.endTransaction();

 if(adc_val > 0x7fffff){ //if MSB == 1

   adc_val = (16777215ul - adc_val) + 1; //do 2's complement

 }

 //Serial.print("AIN0_COM: ");

 //String myString = String((double) adc_val*PGAmulti_1);

 //Serial.println (myString);

 Serial.println((double) adc_val*PGAmulti_1,5);                                          ADD DOUBLE

 //Serial.println(" Volt");

 //Serial.println(adc_val*PGAmulti_1*1000,2);

}

///---------------------------------------------------

Could you check it if there need more adjustment?

So I give you my output waveform. Sorry i don't have SPI simulation software. I give you the Serial Output. If it can help

First Case:

Same Circuit Schematic of Figure 25 in datasheet. AIN0 is 5V AIN1 is 0V DC...

1st problem: I got  3.76953V for all time. How can I get 5V?

2nd problem: I got 4.39453V for one time within 50 times of 3.76953. How to avoid this distort.

Second Case:

Same Circuit Schematic of Figure 25 in datasheet. AIN0 is BNC Red  AIN1 is BNC black  from Signal Generator of 1KHZ Sinwaves 5 amplitude. I got the waveform is

I forgot my reference is 2.5V DC from power supply

I very need your help.

Thanks very much!

Best Wish

Hi Christopher
I mis-clicked /button 'Verify Answer'. I hope I don't make some mistakes.

Hi Yang,

I would recommend reading back your register settings (with the RREG command) to make sure that the device settings are correct after programming the device....Doing that will help you verify the SPI communication.

I think you have delays in the correct locations. In some cases, you many be delaying much longer than you need to be, but that shouldn't be a problem. 

The biggest issue I see is that you appear to read data, then wait for /DRDY, here in the code:

Yang Chang said:

 SPI.transfer(WAKEUP);

 delayMicroseconds(34);                                                     --------------------add one shot delay here

 SPI.transfer(0x01); // Read Data 0000  0001 (01h)

 //delayMicroseconds(10);                                                       ---------Should I delay here??/

 adc_val = SPI.transfer(0);

 adc_val <<= 8; //shift to left

 adc_val |= SPI.transfer(0);

 adc_val <<= 8;

 adc_val |= SPI.transfer(0);

 while (digitalRead(rdy) == HIGH) {} ;                                 ADD to detect if Dready go high to finish one shot

 delayMicroseconds(3);//t 17                                                ADD T17 wait for one shot I used 7.86M

 digitalWrite(cs, HIGH);

 SPI.endTransaction();

You will want to make sure that you wait for /DRDY to go low and then read the data.

I would suggest making sure that the SPI communication is working first, that way you know that you are getting the correct data conversion results from the ADC. From there, I would look at the ADC's raw data to see if it looks correct (don't try to covert to a voltage in software - at least not at first). The problem with trying to test everything all at once is that it becomes very difficult to know where the problem is occurring; however, by validating each step in order (the SPI communication, the raw data results, and then the voltage conversion math) it becomes much easier to debug and work out the problems one at a time.

Best Regards,
Chris

Yang Chang said:

I mis-clicked /button 'Verify Answer'. I hope I don't make some mistakes.

No problem, I was able to disregard the answer on that post.