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CCS: How to improve the RF430FRL152H ADC sampling rate to 20-25Hz

Senhao Zhang
Intellectual 270 points

Other Parts Discussed in Thread: RF430FRL152H

Tool/software: Code Composer Studio

I have read some paper about the RF430FRL152H. But I have no idea for how to improve the RF430FRL152H ADC sampling rate to 20-25Hz?

  • 0
    TI__Mastermind 18265 points

    Hello Senhao,

    if you look at the "Firmware Users Guide" page 8 table 3 you see the relation between the ADC setup and the resulting conversion times:

    http://www.ti.com/lit/pdf/slau603b

    If you need 25Hz sampling rate, resulting in 1 sample every 40ms, you have to select the fastest possible selection. The setup would be CIC filter with a decimation rate of 32 and results in an ADC accuracy of 7 bits. The build in ROM firmware requires 32ms for one sample in this case.

    To repeat the sampling process you can set the "Frequency Register" this value specifies the delay between two samples. Because you need a very short time you have to select "Custom Time" and specify the value in the "Custom Timer Value Register" in milliseconds. Because the firmware has some overhead the shortest time in your case would be 40ms. When using a shorter time a collision error will occur.

    If you have the evaluation hardware available you can try these setting with the demo software available.

    Best regards,

    Helfried

  • 0 in reply to Helfried Vollbrecht
    Intellectual 270 points

    Hello Helfried,

             Thanks for your reply, I think it's very helpful for me.

    Best regards,

    Senhao Zhang

  • 0 in reply to Helfried Vollbrecht
    Intellectual 270 points

    Hello Helfried,

              And I also want to know can I use an external ADC with I2C communication to further improve the sampling frequency? If ok, since the highest data rate in ISO15693 protocol is 26.48 kbits / s, what is the maximum sampling frequency (SPS) of ADC in the passive RF communication scenario? Can analog signal sampling and batteryless RF communication be completed by combining external ADC with I2C communication (SPS = 200) and rf430frl152h?

    Best regards,

    Senhao Zhang

  • 0 in reply to Senhao Zhang
    TI__Mastermind 18265 points

    Hello Shenao,

    I cannot answer the question what the maximum ADC sampling frequency would be in this scenario. In principle this should work with an external ADC connected to the I2C bus. Also the maximum I2C clock rate with 400kHz seems not to be a bottleneck. I am most concerned about the power requirements for the external ADC and if this can be supplied in an passive environment. Timing and power requirements must be carefully evaluated but this a customized design that is beyond what we can support.

    Best regards,

    Helfried

  • 0 in reply to Helfried Vollbrecht
    Intellectual 270 points

    Hello Helfried,

    thanks for your reply, I have understood what you mean, so I would like to know the specific values about the power can be used for external applications when rf430frl125h in batteryless mode? When I use vdd2x pin for external power supply, what is the maximum current?

    Best regards,

    Senhao Zhang

  • 0 in reply to Senhao Zhang
    TI__Mastermind 18265 points

    Hello Shenao,

    for the currents you can draw from the RF430FRL152H please see the FAQ chapter 2.4:

    http://www.ti.com/lit/pdf/sloa247

    Remember this depends on the antenna sizes and the distance to the reader which means it has to be tested in your environment if you can reach these values. 

    Best regards,

    Helfried

  • 0 in reply to Helfried Vollbrecht
    Intellectual 270 points

    Hello Helfried,

    Thanks for your reply, love u~ :)

    Best Regards,

    Senhao Zhang