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TMS320F28379D: 请问该型号的ADC采样率最大3.5Msps是如何计算得来的

Liu HengYi
Prodigy 10 points
Part Number: TMS320F28379D


如题，怎么计算在单端模式下，单个ADC采样率最大是3.5Msps，手册也没有提及到

  • +1
    Prodigy 50 points

    同问，我用单通道软件FOR循环也就有大概660Ksps的采样率

  • +1 回复 Xiao Wu
    TI__Mastermind 39885 points

    我咨询下相关工程师后回复您。

  • +1 回复 Ben Qin
    TI__Mastermind 39885 points

    参考下工程师的回复：

    To calculate the ADC sample rate, add the chosen ACQPS value in seconds with the tEOC (also in seconds) and then take the inverse of this number:

    Sample rate = 1 / (ACQPS + tEOC)

    ACQPS: Sample-and-hold time; minimum of 75 ns based on hardware, provided by the datasheet (8.10.1.2.3 ADC Operating Conditions (12-Bit Single-Ended Mode))

    tEOC: Time from the end of the sample-and-hold window until the nextADC conversion can begin; provided in SYSCLKs, with a minimum of 44 based on the device frequency and maximum ADC clock frequency (provided by the datasheet in section 8.10.1.2.3 ADC Operating Conditions (12-Bit Single-Ended Mode))

    Make sure the ACQPS and tEOC are in the same units before using them in the above equation (here I've assumed you were talking about 12-bit single-ended mode). 

  • 0 回复 Ben Qin
    Prodigy 50 points

    嗯嗯，我同意最大采样率是如此计算，但是在C200wave的例程中，adc_ex2_soc_epwm.c，这个例程，采样窗口（ACQPS）是15个时钟周期，也就是75ns，我通过改变epwm的频率从而去控制ADC的采样率，但是最大只能达到大约500Ksps~600Ksps的速度，请问要如何才能达到3M左右的可控采样率呢？

    下图是我根据例程adc_ex2_soc_epwm.c配置的采样率，再大读取的波形就不正确了。

  • 0 回复 Xiao Wu
    TI__Mastermind 39885 points

    参考下工程师的回复：

    This example only uses 1 ADC, which will have some delay because it's doing 1 conversion and then reading that result. The best way to try and achieve a higher sampling rate is using many SOCs (all if possible). You can trigger the first SOC however you want and then have each EOC trigger the next SOC so that you are getting continuous conversions. If you are having the ePWM trigger each conversion on 1 SOC, the throughput of the ADC will most likely be lower than the maximum possible.

    Also, keep in mind that depending on how long the ISR is (this example seems okay, but a customer use-case may vary), the sampling rate may be affected as well as the accuracy of the result.

  • 0 回复 Ben Qin
    Prodigy 50 points

    嗯，我在尝试例程adc_ex6_soc_continuous_dma的时候也发现了采样率能达到2Msps，但是如果我需要设计ADC的采样率较高，且可控，连续采样时候的采样率似乎不可以控制。请问有什么方法可以解决这个问题呢？