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[FAQ] PGA900: Questions Regarding Communication to the PGA900, PGA300, PGA302 and PGA305 Devices

Bob Benjamin
Guru** 113765 points
Part Number: PGA900
Other Parts Discussed in Thread: PGA302, PGA300, , PGA305

Tool/software:

I have some general questions regarding communication relating to the PGA900, PGA300, PGA302 and PGA305.  The main questions are as follows:

  • Why am I having issues with my communication?
  • How to I get the OWI to work?
  • 0
    TI__Guru** 113765 points

    The PGA300 has OWI communication only.  The PGA302 and PGA305 have OWI and I2C digital interfaces for communication.  The PGA900 has SPI, I2C, OWI and UART (signals shared with the SPI interface and requires activation as the SPI is default).

    See the following sections for the answers to the above questions:

    Bob Benjamin said:
    Why am I having issues with my communication?

    The most common areas of communication difficulty are when using the OWI (one-wire) interface (see below for additional details).  Another common issue when trying to directly communicate to device registers is the M0 is not in the reset state or the digital interface being used has not been enabled.  Another possible issue is not following the correct protocol format for the desired operation.  See the device datasheet for specific details.

    Bob Benjamin said:
    How to I get the OWI to work?

    The OWI (one-wire interface) uses supply voltage variations to talk to the PGA device and returns messages by varying the current.  Details regarding the required timing and voltages used are given in the PGA device datasheet.  The most common issues relate to the voltages not being correctly applied to the PGA supply input to start OWI activation, or that activation timing sequence is not being followed correctly.  The voltage and timing can be observed and verified using an oscilloscope.

    If the EEPROM is in the locked condition, the unlock command (0x5555) must be sent immediately after activation.