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Original question:

ADS1118EVM: ADS1118EVM returns railed data. Configuration Correct?

ADS1118EVM: Config and Temperature Addresses?

Jim Michaud
Prodigy 90 points
Part Number: ADS1118EVM
Other Parts Discussed in Thread: ADS1118,

Joseph,

Looks like I have your application reading ADS1118 with your COTS software, thank you.

I have to read the ADC1118 device through an Aardvark I2C_SPI adapter manufactured by TotalPhase.

I currently write/read of two bytes [0xB7, 0x83] for the config.  I can see the bytes echoed back in the response buffer but do not get a temperature.

Do I need to "point" to the memory address for the configuration when I write it?  And then do I need to "point" to the temperature register and do another read?

How does your application read the config and temperature registers?  Are there any delays between the configuration write and the temperature request?

Regards,

Jim  

  • 0
    TI__Guru* 95565 points

    Jim,



    Generally I think the best way to use the device is through single-shot conversion mode. For this mode, you would:

    1. Write the configuration register

    2. Wait for the conversion to complete (1/data rate + 10%)

    3. Read the conversion back.

    4. Repeat as necessary.

    I would note that in continuous conversion mode, it's similar, but when you program the configuration register, the device completes the conversion in progress, and then writes the new configuration register.

    Note that the internal temperature sensor uses the ADC for reading the temperature. This way, it's like having another multiplexer setting. Note that you can't do an ADC reading and a temperature reading at the same time.

    There is a cookbook circuit using this device I wrote last year. There's more information than you probably need, but the pseudocode that's in the note may be useful. You can find a link below:

    http://www.ti.com/lit/an/sbaa354/sbaa354.pdf

    This circuit is set up in a data rate of 8SPS, and I use the 32-bit transmission cycle to configure and read out the device. However, you can tailor that to what you need.



    Joseph Wu

  • 0 in reply to Joseph Wu
    TI__Guru* 95565 points

    Jim,

    In the ADS1118EVM software, the GUI alternates between temperature readings and ADC readings. The temperature sensor is enabled in the ADC with bit 4 of the configuration register.

    There will always be a delay between programming the configuration register and getting the data back. It's nominally (1/data rate). Because there is some variation in the internal oscillator, you should add 10% to that time period.


    Joseph Wu

  • 0 in reply to Joseph Wu
    Prodigy 90 points

    Joseph,

    Thanks for helping.  I'm using the Aardvark and their COTS utility to talk to the ADS1118.  Hopefully I've attached enough pictures.  When sending BD 0B, all I'm getting back is 00 00.  Also tried the same code you reference in your paper.   Still not sure what is going on.  Thinking that the Aardvark delays during the write/read but I cannot verify. 

    Here's my setup on paper.

    Aardvark Config:

    Output:

  • 0 in reply to Jim Michaud
    TI__Guru* 95565 points

    Jim,


    When making physical connections like this, I highly recommend getting an oscilloscope or logic analyzer to look at the digital signals going into and out of the device. You can verify that the signals are going where they should. You need something other than the Total Phase Control Center software to verify the signals. At this point I think you have some incorrect connections.

    First, lets look at the Aardvark pins. The last 6 pins are what you care about:
    5. MISO
    6. +5V
    7. SCLK
    8. MOSI
    9. SS
    10. GND

    From the photo, your wire connections to the Aardvark adapter are:
    5. Yellow
    6. Orange
    7. Red
    8. Brown
    9. Black
    10. White

    However your connections based on the photos to the ADS1118 are:
    5. Yellow should be to MISO (DOUT), but is connected to DIN
    6. Orange is connected to VDD
    7. Red is connected to SCLK
    8. Brown should be connected to MOSI (DIN) but is connected to ground
    9. Black is connected to SS (/CS)
    10. White should be connected to GND, but is connected to DOUT

    From the photos, it's hardest to see the connections to the Aardvark adapter, so you'll need to verify the pins. However, it does look like you have a bad set of connections.

    I would note that I have an Aardvark too. I've used it to talk to many devices, including the ADS1118. I built up a board with pin labels that I connect to the Aardvark adapter. It also has connections to another set of headers that I use to connect to other boards and oscilloscope probes.


    Joseph Wu