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Re: ADS1147 SPI Communication

Mohd Uzair
Prodigy 10 points

Other Parts Discussed in Thread: ADS1147

HI,

Somebody please tell me the spi commands for initial settings and reading converted data....

This is the connection ,a using atmel controller.. I connected a 120 resistor at  J2(1&2),Value at the output is 32767 which i guess not ideal...

Regards,

Thanks

  • TI__Guru** 113765 points

    Mohd,

    Welcome to the forum!  From the digital side, you must have the RESET pin high and the START pin high for the ADS1147 to convert the analog to digital.  You will need to review the datasheet and follow the command sequence and set the registers appropriately.  Default values will get you part way there as AIN0 and AIN1 are selected as inputs and REF0 is selected as the reference.  You will need to turn on the internal reference and set the IDAC outputs to your desired value and to AIN0 and AIN1.  The write register command is basically a 0x40 command plus the starting register address, the second byte is the number of registers to write minus 1, and the following bytes are the bytes you wish to write to the register.  So for the MUX1(0x02) register you need to make sure the internal reference is turned on as it is needed for the IDAC reference so the MUX1 register needs binary 00100000 (0x20).  So the command for this would be 0x42 0x00 0x20. 

    Then in the IDAC0 register (0x0A) you need to set the desired current.  I will use 250uA for each IDAC as an example.  00000011 (0x03).  For IDAC1 register (0x0B) you need to send the IDAC output to the analog inputs. 00000001 (0x01) is written to that register.  So the command for these two register writes would be 0x4A 0x01 0x03 0x01.

    You must also make sure that the input is within the common mode input range, so R3 must be calculated appropriately.  See the Design Notes page for further information:

    http://e2e.ti.com/support/data_converters/precision_data_converters/w/design_notes/input-voltage-range-requirements-for-the-ads1248-and-ads1148-families.aspx

    Best regards,

    Bob B