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slave device is not responding(i.e showing 0x00) in ssi communication

kumpal patel
Prodigy 30 points
Other Parts Discussed in Thread: TM4C1232D5PM

I am trying to communicate ti’s TM4C1232D5PM (ARM Cortex M4 based) as a master and linear’s LTC2983 as a slave by SSI protocol.

I have used SSI2 module for interfacing, port PB4,PB5,PB6,PB7 is used as CLK,FSS,RX,TX respectively

As I have checked many times in logic analyser and I found that Master device is working properly it sends all data through SSI2TX (MOSI ) as per data given.

On other side from slave I am not getting any response and thus it is showing 0x00 in logic analyser in MISO pin i.e slave output pin SDO.

So whatever data I pass through MOSI ,it always gives 0x00 on MISO of master.

i have used freescale mode 0

i am trying to read slave device register as per slave device datasheet instruction but it is not resp[onding

can any one help?

  • 0
    TI__Guru**** 244380 points
    Hello Kumpal

    If the slave device is not working, then I bet you need to ask Linear Technology....

    Check is the power, GND and reset pins are in proper order and as per the specification of the slave device
  • 0 in reply to Amit Ashara
    Prodigy 30 points
    Thank u so much for reply..Amit ashara
    As you preferred I have checked that power and ground are applied properly with 5 volt as per specs.. But reset I haven't configured,I.e have kept it open..
    Also on applying power as per data sheet it respond with interrupt pin as logic high on startup of device... So I checked it in logic analyzer ,but it is not showing any peak or high level on interrupt pin.. What should I do as next step to verify...pls suggest me Amit if u have any idea.
  • 0 in reply to kumpal patel
    Guru 47900 points

    kumpal patel said:
    But reset I haven't configured,I.e have kept it open..

    That's a key fact - is it not?

    Unless your Slave device includes an internal pull-up/down - allowing the critical reset pin to "float" (the result of "open") strays far from "Best Practice."

    Treat (both) the Slave's Reset and Interrupt pins as directed by its data-sheet - sure to define such...

  • 0 in reply to cb1
    TI__Guru**** 244380 points
    Hello cb1

    And it seems that the datasheet does not mention any Pull Up internal to the slave device is available.
  • 0 in reply to Amit Ashara
    Prodigy 30 points

    thank u so much amit and cb1.. today i am going to make a reset pin as a pull up..and test the device.. will update soon with upcoming status..

    thank you

  • 0 in reply to kumpal patel
    Guru 11940 points

    To second cb1 and Amit again - reading and digesting the datasheet is always a recommended practice. There is nowhere a pull-up on this reset pin mentioned. And pages 53 and 54 show application circuits, with this pin tied to Vcc (+2.85..5.25V).

    And, a scope or logic analyzer is heavily recommended. Carefully compare the waveforms of your circuit/application with that of the datasheet. The state of the reset pin might not be the only problem ...