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TMS320F280049: Simultaneous sampling with single ADC

Vineeth N
Expert 1180 points
Part Number: TMS320F280049


Hi Team,

I am using 280049 DSP for my project. I have several external readings to be measured and some of them are to be measured simultaneously. My aim is to measure three signals synchronously for more precise reading. My doubt is that can I use a single adc, ADC-A for instance for simultaneous sampling of three signals at its three input channels say ADCIN1-3. Or should I use three different adcs ADCA-C for achieving simultaneous sampling.

Is burst mode a solution for this?. Since I have a doubt that will two SOCs will initiate conversion at the same time (Pg.no. 1489 TRM). Or is it like that in burst mode a single trigger will initiate conversion of two SOCs one after other ?. 

Thank you,

Vineeth N

  • 0
    TI__Guru 60865 points

    Hi Vineeth,

    Generally the best method for simultaneous sampling would be to use 3 ADCs in parallel as this will produce samples that are exactly simultaneous.

    However, you can definitely just use one ADC, but the samples will occur sequentially based on the ADC sampling time.  For F280049, the minimum time between samples is about 300ns; you'll need to decide if this is "simultaneous enough" for your application. 

    You won't need burst mode to accomplish this, instead you would set 3 SOCs to use the same trigger:

    e.g.

    SOC0 = ePWM3A trigger, S+H = 100ns, CH = A2

    SOC1 = ePWM3A trigger, S+H = 100ns, CH = A0

    SOC2 = ePWM3A trigger, S+H = 100ns, CH = A3

    When the trigger arrives, all 3 SOCs will be set to pending, and the ADC will convert them sequentially per the configured priority scheme (for the default Round-Robin scheme, these will resolve SOC0-->SOC1-->SOC2)

    Finally, one more trick is available if you are using a single ADC: take multiple samples per channel per trigger that have the same average time

    e.g. Sample A2 --> A0 --> A3 --> A3 --> A0 --> A2 using 6 SOCs and then average the like channel results together.  Each average conversion will have the same average time.