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PGA460: System Diagnostics command

Peter Karlsen
Prodigy 10 points
Part Number: PGA460

Hi,

I'm trying to get a PGA460 tuned to work well with my transducer setup.

It seems that the datasheet (SLASEJ4A) is a unclear in some points.

I use the uart interface for communication. 

In the  UART interface command list (Table 3), it says that the system diagnostics command (8) should return 3 bytes. Transducer voltage, transducer frequency and decay period time

When I use the EVM GUI software with the EVM module, all I get is 2 bytes between the diagnostic data field and a checksum field. 

I guess the first byte is related to the frequency of the transducer, but I cannot find anywhere how the returned value translates int a frequency. 

The second byte seems to relate to the decay time. Decay time = value * 16us

Can you confirm, that the System Diagnostics actually only returns 2 bytes and how to interpret the returned values?

Regards,

Peter

  

  • 0
    TI__Mastermind 27950 points
    Hi Peter,

    You must be using the old/original version of the PGA460 datasheet, which contains a few errors in Table 3, including Cmd8. If you refer to revision A of the dataheet (currently available online at www.ti.com/.../pga460-q1 ), Cmd8 only returns 2 bytes as you have observed, where Byte 1= Transducer frequency and Byte 2 = Decay period time.

    To convert the raw frequency diagnostic byte value into a kHz equivalent refer section "7.3.5 System Diagnostics" equation 5 in the datasheet:
    f = 1 / (FDIAG_VAL × 500e–09)