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ADS1262: ADC1 Output Data

JAOverstreet
Intellectual 650 points
Part Number: ADS1262


I am trying to get a better understanding of the output data from the ADS1262. I have a +1V signal connected between AIN0 and AINCOM. The output does change when the signal level changes, however the data the ADC is getting back does not seem to make much sense.

DATA[0] DATA[1] DATA[2] DATA[3] DATA[4] DATA[5] A=DATA[1] << 24 B=DATA[2] << 16 C=DATA[3] << 8 D=DATA[4] F=A||B||C||D F>>31 H=F && 32767 I=H*2.5V/2^(31)
65 115 238 139 206 85 1929379840 15597568 35584 206 1945013198 0 3022 3.51807E-06
65 116 2 45 243 49 1946157056 131072 11520 243 1946299891 0 11763 1.36939E-05
65 115 250 47 15 70 1929379840 16384000 12032 15 1945775887 0 12047 1.40246E-05
65 115 252 148 195 97 1929379840 16515072 37888 195 1945932995 0 5315 6.18747E-06
65 115 252 182 243 179 1929379840 16515072 46592 243 1945941747 0 14067 1.63761E-05
65 115 224 124 68 174 1929379840 14680064 31744 68 1944091716 0 31812 3.7034E-05
65 115 244 109 125 236 1929379840 15990784 27904 125 1945398653 0 28029 3.26301E-05
65 115 243 109 79 189 1929379840 15925248 27904 79 1945333071 0 27983 3.25765E-05
65 116 3 204 161 127 1946157056 196608 52224 161 1946406049 0 19617 2.28372E-05
65 115 237 22 230 247 1929379840 15532032 5632 230 1944917734 0 5862 6.82427E-06
65 115 249 119 253 123 1929379840 16318464 30464 253 1945729021 0 30717 3.57593E-05
65 115 243 126 64 191 1929379840 15925248 32256 64 1945337408 0 32320 3.76254E-05

The status byte says the ADC is being constantly reset, and the voltage is not where near 1V. I have checked the input multiplexer configuration and that register does read 0x0A. Does anyone have some suggestions on why this data looks so weird or is my conversion incorrect?

Thanks,

Allan

  • 0
    TI__Guru 54166 points

    Hi Allan,

    Let me request some information in order to further assist you here:

    • Are you using the ADS1262EVM to read back data, or are you using your own board?
    • Can you provide the hex values of the data you receive (all 6 data bytes if you have STATUS and CRC enabled)?
    • Can you tell me your ADC reference voltage and the gain setting you are using to take this data?
    • Can you read back all register settings after taking data and send this to me as well?

    For the RESET question: the RESET bit needs to be cleared in the Power register by the user or the Status byte will always show that the device has just been RESET. See section 9.4.10 for more information on how the RESET bit in both registers behaves (as well as the register map, pg. 70 and pg. 89)

    -Bryan

  • 0 in reply to Bryan Lizon86
    Intellectual 650 points

    Hi Bryan,

    • Are you using the ADS1262EVM to read back data, or are you using your own board?
      • This is a custom board.
    • Can you provide the hex values of the data you receive (all 6 data bytes if you have STATUS and CRC enabled)?
      • Yes please see the table below. AIN1-AINCOM voltage is 0.5V.
      • Data[0] Data[1] Data[2] Data[3] Data[4] Data[5]
        41 19 88 A3 0E ED
        41 19 88 B8 21 15
        41 19 88 A2 F0 CE
        41 19 88 D6 3B 4D
        41 19 88 99 41 16
        41 19 88 8C 92 5A
        41 19 88 78 61 15
        41 19 88 A8 B7 9B
        41 19 88 A1 CE AB
        41 19 88 D3 73 82
        41 19 88 C7 56 59
        41 19 88 BE 3 FD
        41 19 88 B3 8F 7E
        41 19 88 86 8 CA
        41 19 88 E6 E2 4
        41 19 88 CA 0 6
        41 19 88 55 54 E5
        41 19 88 9F 5D 38
        41 19 88 B1 25 12
        41 19 88 CA ED F3
        41 19 88 6B 69 10
        41 19 88 B2 D7 C5
        41 19 88 CC 42 4A
        41 19 88 74 14 C4
        41 19 88 B5 EE DF
        41 19 88 E8 A1 C5
        41 19 88 AB 3B 22
        41 19 88 D1 58 65
        41 19 88 A2 1E FC
        41 19 88 D5 68 79
        41 19 88 DD 68 81
        41 19 88 E0 D5 F1
    • Can you tell me your ADC reference voltage and the gain setting you are using to take this data?
      • I am using the internal voltage reference, so 2.5V.
      • The gain is set to the default of 1.
    • Can you read back all register settings after taking data and send this to me as well?
      • Yes please see the table below. ADC reading on bottom row was performed first.
      • Register Data[0] Data[1] Data[2] Data[3] Data[4] Data[5]
        0x1A 41 19 40 0
        0x19 41 19 0 0
        0x18 41 19 0 0
        0x17 41 19 0 0
        0x16 41 19 1 0
        0x15 41 19 0 0
        0x14 41 19 0 0
        0x13 41 19 0 0
        0x12 41 19 0 0
        0x11 41 19 0 0
        0x10 41 19 0 0
        0xF 41 19 0 0
        0xE 41 19 0 0
        0xD 41 19 BB 0
        0xC 41 19 40 0
        0xB 41 19 0 0
        0xA 41 19 0 0
        0x9 41 19 0 0
        0x8 41 19 0 0
        0x7 41 19 0 0
        0x6 41 19 0A 0
        0x5 41 19 4 0
        0x4 41 19 80 0
        0x3 41 19 0 0
        0x2 41 19 5 0
        0x1 41 19 11 0
        0x0 41 19 3 0
        ADC_READ 41 19 88 77 86 39
  • +1 in reply to JAOverstreet
    TI__Guru 54166 points

    Hi Allan,

    When I convert the values in the table you provided from hex to voltage, I am getting 0.4987 V each time. This corresponds well to your input voltage of 0.5V.

    For example, the first conversion result you get is 1988A30E, which is comprised of Data[1] through Data[4] (Data[0] is the STATUS byte while Data[5] is the CRC byte). This conversion result is 428385038 in codes (or decimal). One LSB for the 32-bit ADS1262 at VREF = 2.5V and G = 1 is 1.164 nV. Multiplying the LSB by the code gives you 0.4987 V.

    Therefore, I believe the ADC is working as you intended. You can reference our ADS1262 Excel-based calculator tool for help converting code to voltage, as well as several other useful tools: https://www.ti.com/lit/zip/sbac137

    -Bryan