16 bit ADC (AD7715) prototyping board

AD7715AD7715:

The AD7715 is a complete analog front end for low frequency measurement applications. The part can accept low level input signals directly from a transducer and outputs a serial digital word. It employs a Σ-Δ conversion technique to realize up to 16 bits of no missing codes performance. The input signal is applied to a proprietary programmable gain front end based around an analog modulator. The modulator output is processed by an on-chip digital filter. The first notch of this digital filter can be programmed via the on-chip control register allowing adjustment of the filter cutoff and output update rate. The AD7715 features a differential analog input as well as a differential reference input. It operates from a single supply (3 V  or 5 V). It can handle unipolar input signal ranges of 0 mV to 20 mV, 0 mV to 80 mV, 0 V to 1.25 V and 0 V to 2.5 V. It can also handle bipolar input signal ranges of ±20 mV, ±80 mV, ±1.25 V and ±2.5 V. These bipolar ranges are referenced to the negative input of the differential analog input. The AD7715 thus performs all signal conditioning and conversion for a single channel system. The AD7715 is ideal for use in smart, microcontroller, or DSP-based systems. It features a serial interface that can be configured for three-wire operation. Gain settings, signal polarity, and update rate selection can be configured in software using the input serial port. The part contains self-calibration and system calibration options to eliminate gain and offset errors on the part itself or in the system.

Protoboard is assembled with AD7715 and precision voltage reference REF5025. The AD7715 is ideal for bridge applications (like weigh scales, pressure transducers, thermometers, etc…) with ratiometric differential input and integrated PGA. PCB is single-sided.

All project files are here:

 

 

Assembled module:

AD7715 + REF5025

AD7715 + REF5025 prototyping module

2 Comments

  1. I am a student of electronics from Argentina. I have problems with the AD7715 to communicate with a freescale QG8. You distribute the software or more prototivo communications driver? what is its cost?

    Thank you very much and I look forward to your comments

  2. Mare says:

    Hello!

    I have some old code for AD7715. I hope it will help you. It is in c, which could be easy portable to any microcontroller. All you have to do is to define macros for toggling GPIO pins and reading GPIO pins.

    /* procedures for AD7715 - quick and dirty access with bitbanging *********/      
    // send one byte to AD
    void ad_out(unsigned char dat)
    { unsigned char J;
      for (J=0; J<8; J++)
      {
        AD_CLK = 0;
        wait(1);
        AD_D=dat & 0x80;
        AD_CLK = 1;
        wait(1);
        dat=dat < < 1;
      }
    
    }
    
    
    // Read one byte from AD
    unsigned char ad_in(void)
    { unsigned char J,K,dat;
      K = 128;
      dat = 0;
      AD_D=1;
      for (J=0; J<8; J++)
      {
        AD_CLK = 0;
        wait(1);
        if (AD_D) { dat=dat+K; }
        K=K >> 1;
        AD_CLK = 1;
        wait(1);
      }
      return dat;
    }
    
    /* Wait for DRDY to go low */
    void ad_cakaj(void)
    {
      DRDY=1; while(DRDY);
    }
    
    // Read one conversion result from AD at given gain
    unsigned int ad_beri(unsigned char gain)
    { unsigned int vrednost;
    
      ad_cakaj();
      ad_out(0x38+gain);
      vrednost=ad_in();
      vrednost< <=8;
      vrednost+=ad_in();
    
      return vrednost;
    }
    

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