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Example program for EVAL-CN0540-ARDZ: System Default Configuration

Category: Software
Product Number: EVAL-CN0540-ARDZ
Software Version: 1:9dd7c64b4a64

The Circuit Note CN-0540 says:

System Default Configuration

A default configuration of the system for narrow bandwidth measurement was chosen as follows for the ADC settings:

 MCLK divider: MCLK/16

 Power mode: low power mode

 FIR filter with decimation over 32

 VCM pin output: (AVSS − AVDD)/2

 Reference (REF) buffers: precharge on

 Analog input (AIN) buffers: precharge on

 MCLK frequency of 16.384 MHz

 FDA enabled, in low power mode

 DAC buffer enabled

 DAC output set to half scale

[emphasis mine]

I'm trying to figure out how the FDA default is supposed to be Low Power Mode. Looking at the schematic, I see 

I'm not entirely sure, but I think this hardware sets the FDA to Full Power Mode by default. There is also this:

so I believe that the software can override the hardware default FDA power mode by writing to GPIO3. However, I don't see anything in Example program for EVAL-CN0540-ARDZ  that would do that by default. There is a 5  - Set ADC to default config"  option, but it doesn't seem to touch the FDA. The only way that I've found to accomplish it is to 

  1. 11 - Set ADC GPIOs
  2. 4 - Change GPIO settings
  3. 1 - Enable all GPIOs (Global enble)
  4. 11 - Set ADC GPIOs
  5. 3 - Set GPIO as input / output
  6. 5 - Set GPIO3
  7. 2 - Set GPIO3 as output

So, in what sense is FDA Low Power Mode the system default? What am I missing?



Added link to Example Program
[edited by: CK3 at 3:00 AM (GMT -5) on 25 Nov 2022]

 Hi CK3,

From what I think the initialized software does for the various controller platforms supported, I don't believe the FDA is set to low power mode by default.  What I think is written in the circuit note is that the some of the plots/values were taken using that low power FDA mode enabled.    can you please help clear this up a bit?

Cheers,

Brandon

  • From what I think the initialized software does for the various controller platforms supported, I don't believe the FDA is set to low power mode by default.

    I wonder why full power mode was chosen as the default when the Circuit Note says "The ADA4945-1 FDA is set to low power mode. In full power mode, the FDA can provide wider bandwidth and better linearity performance. However, because the bandwidth of interest in this design is less than 50 kHz, low power mode is sufficient [emphasis mine]." 

    Anyway, I modified my port of the Example Program to set the FDA to low power mode at initialization time.

  • FormerMember
    0 FormerMember on Jan 18, 2023 3:54 PM in reply to CK3

    Hi Ck3,

    Closing out this ticket for now.  If there is anything else that comes up, please open a new thread.