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ADS1298 ID Register

Patrick McCloskey
Expert 1015 points
Other Parts Discussed in Thread: ADS1298, ADS1294R, ADS1294, ADS1296, ADS1296R, ADS1298R

Hi folks:

I am ramping up some work involving the ADS1298 ECG analog front-end device.

When I read the ID register on the ADS1298, I get 52h.  From the description of the ID register (address: 00h) on page 46 of the ADS129x datasheet, I expect ID=92h.

However, in section 5.9 "Register Map" of the ADS1298ECG-FE Performance Demonstration Kit User's Guide (SBAU171A), the value for the ID register is listed as 0x52, which is the same value I get.

I inherited a custom prototype setup using the following:

  a) TMS320C5515 EVM  assembly 512700 rev B

  b) Actel AGLN250 nano FPGA starter kit board

  c) ADS1298ECG-FE Performance Demonstration Kit  rev A with ADS1298ZXG 9AZEZ89GJ

Is ID=52h correct for ADS1298ZXG 9AZEZ89GJ ?

Do I have a problem that I should resolve?

Thanks in advance for any guidance!

PJ

  • TI__Expert 3260 points

    Hello Patrick,

    Can't really speak for the rest of your setup, but the ID register is independent. This is a Factory-Programmed, Read-Only register, and is completely dependent on the specific device (chip itself) you have. If you compare the device you have with page 46 of the ADS1298 Datasheet, you will find out what it is supposed to read as.

    So, in your case:

    "BIT 7        BIT 6        BIT 5     BIT 4       BIT 3       BIT 2            BIT 1       BIT 0

    DEV_ID7 DEV_ID6 DEV_ID5    1              0          DEV_ID2     DEV_ID1  DEV_ID0

    Bits[7:5] DEV_ID[7:5]: Device family identification

    These bits indicate the device family.

    000 = Reserved

    011 = Reserved

    100 = ADS129x device family

    101 = Reserved

    110 = ADS129xR device family

    111 = Reserved

    Bit 4 This bit reads high.

    Bit 3 This bit reads low.

    Bits[2:0] DEV_ID[2:0]: Channel number identification

    These bits indicates number of channels.

    000 = 4-channel ADS1294 or ADS1294R

    001 = 6-channel ADS1296 or ADS1296R

    010 = 8-channel ADS1298 or ADS1298R

    011 = Reserved

    111 = Reserved"

    [100 for 129x device family] [10 for bits that are constant][010 for 1298] => So, 1001 0010 (92h), assuming that you have the ADS1298 device (which your part number suggests you do).

    Now, there are only a couple of possibilities as to why yours is reading back incorrectly. 1) power-up/reset sequence needs another look, or 2) CS might be floating. Please check your power-up/reset sequence, such that it corresponds to the datasheet specs, and make sure your chip select isn't floating, and it should fix your issue.

    Regards,

    Michael

     

  • TI__Guru**** 181781 points

    Hi PJ,

    I understand you are working with Carl on this issue.  Have you resolved it yet?

  • in reply to Tom Hendrick
    Expert 1015 points

    After working with Carl Wolfe, TI Analog Field Applications Engineer, we concluded that my ECG FE PDK had pre-production silicon.

    I now have a newer ECG FE PDK with production silicon. Here are the markings on the ECG front-end chip:

    ADS1298

    04ZDV09G1

    With this PDK installed in my setup, I read value 92h from the ID Register (register 00h), as expected.

     

    I paid close attention to the Power-Up Sequencing section of the ADS1298 datasheet, as Michael W suggested. After some changes in my initialization code, I no longer saw SPI readback problems the first time after powering up the ECG FE PDK. Thanks for the suggestion, Michael.

  • in reply to Patrick McCloskey
    TI__Expert 3260 points

    Great! Seems your situation was certainly uncommon. But, I'm very glad to hear that your dilemma was resolved.