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Original question:

Compiler/ADS8638: Aurdino based Itsybitsy m4 express interfacing with AD8638 chip.

Compiler/ADS8638: Compiler/ADS8638: Aurdino based Itsybitsy m4 express interfacing with AD8638 chip.

Suresh kumar
Prodigy 45 points
Part Number: ADS8638

Tool/software: TI C/C++ Compiler

Hello Dale,

Sorry for delay in response.

this issue continuation of https://e2e.ti.com/support/data-converters/f/73/t/893830 

-As per the SPI MOSI getting Spikes at the end of the 8-bit frame.

1. Is it a correct Senario or not .........?

2. If yes why?. As per SPI frame this is not right.

3. If  this is correct Scenario..will the slave ADS8638 chip gets responded correctly?.

4, If this is wrong Scenario how to reove the spikes..

Thanks 

Suresh.

  • 0
    TI__Mastermind 39155 points

    Hi Suresh,

    No worries. The signal you highlighted is MOSI which is a data signal from your controller to the ADC, and these pulses are caused by your controller because this signal is always high if you look at the same data signal before and after sending out SCLKs (idle status). These additional pulses will be ignored by the ADC because they are only showing up between the effective SCLK clocks and they are not showing in a effective SCLK clock.

    Note that the DIN data on the MOSI will be latched by the ADC at every rising edge of the SCLK. Each data bit on the MISO can be latched (read) on the next falling edge of SCLK from the SCLK falling edge on which the respective data bit is clocked out.

    One thing I should let you know, all analog ground( AGND) and digital ground (DGND) on the ADC should be connected together on a solid ground plane, your schematic in your previous post does not show a connection between these separate ground pins.

    Best regards,

    Dale

  • 0 in reply to Dale Li
    Prodigy 45 points

    Hello Dale,

    yes we have connected the pins.
    - As per your Comment if MOSI is correct we are unable to receive the data in MISO pin.
    Can you please Specify the reasons.

  • 0 in reply to Suresh kumar
    TI__Mastermind 39155 points

    Hi Suresh,

    I need more information to address the issue. As I asked in your another post, I need a scope shot of the digital communications lines together including /CS, SCLK, DOUT and DIN, and it will be great to have screen shots of timing that is zoomed in a closer for your writing and reading operations. Also, please let me know  your configurations to the ADC.

    Thanks&regards,

    Dale