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multiple analog sensors with high sampling rate

Ali Kubba
Intellectual 470 points
Other Parts Discussed in Thread: MSP430F2274, MSP430F1611

Hi All,

I would like to use the eZ430-RF2500 tool kit to manage inputs and outputs for 4 sensors under 500Hz sampling rate per each sensor (so all the 4 sensors should receive and give feed back 500 readings in each second)

there is another chip which generate the necessary analog input signals and capable of receiving the whole four sensors outputs (8kHz band width)

Can I use eZ430-RF2500 tool kit for this purpose?

Many thanks

Ali

  • 0
    Expert 1710 points

    It seems like the ez430-RF2500 target board could work usefully for reading analog inputs from four sensors and digitizing each at 500Hz sampling rate via a unique ADC input on the MSP430F2274 on the RF2500 board and sending the digital data for each of the four samples over the RF link as data at the required sample rate.

    You would have to look at the schematics in the ez430-RF2500 target board's user guide document (document code SLAU227E on the TI site) and see how you would properly interface and solder your sensor interface chip to the RF2500T target board's available ADC analog input pins from the MSP430F2274 and then you should just be able to program the MSP430 to digitize those four inputs and send the data over the wireless link.

    If you're sampling 16 bits (2 bytes) per sample at 500 Hz for four sensors that would be 2 kBy / sec or 2kSamples/sec, so maybe your 8kHz bandwith comment above was in error.  Anyway the ADC converter on the MSP chip should be capable of sampling the four samples even faster than your requirement, and the radio should be able to transmit data far in excess of your requirement, so the concept seems feasible.

     

  • 0 in reply to C. Hayes
    Intellectual 470 points

    Hi Hayes,

    Thanks for the reply.

    Is it OK to use the kit in such a way that the sensors feedback sent as analog signal to the other chip?

    Ali

  • 0 in reply to Ali Kubba
    Expert 1710 points

    Hi,

     

    I am not sure I understand where you want to generate the analog signals.  If at the location of the sensors themselves you must generate analog feedback or output signals it seems like you must do that with the added chip you are using to interface between the sensors and the MSP430 ADC inputs.  The MSP430F2274 on the RF2500T board does not seem (my quick impression) to offer analog signal output generation capabilities other than the very basic possibilities you could construct with a GPIO output pin or PWM output pulse wave form with the addition of other analog filtering / processing components.

    If you mean that on the other side of the RF link opposite from the original sensors you wish to regenerate the analog signals transmitted from the remote sensors via wireless link, I think you should look at constructing a 4-channel DAC to interface to the RF receiver module's circuit (also the RF2500T's MSP430F2274 I guess is what you might use on a different peer module?) and use the DAC to generate the four analog outputs corresponding to the digital sensor sample data received over the RF link.  Otherwise you could implement a PWM based DAC with a digital timer output and a low pass filter of a signal coming from the MSP430F2274's timer output pin (if the timers / CCRs are free to generate enough such outputs), but you'll need to assess whether the quality / resolution of the PWM outputs will be sufficient for your needs, and you'd need to pick the appropriate low pass filter and amplifier / buffer implementation to suit the voltage and impedance output range you require from the sensor outputs.

    If the amount of circuitry you are adding is not trivial to interface to the RF2500T module, you might as well look and see if you can just build another little board that has the analog signal processing circuitry, sensor interfaces, DAC or PWM outputs as needed, and maybe do that with the help of an added MCU which could (you'd have to investigate the options) communicate digitally to the RF2500T's MSP430F2274 via SPI or I2C (just my conjecture as to whether that would be easy).

     

     

     

     

  • 0 in reply to C. Hayes
    Expert 1150 points

    Hi,

    I'm facing some problem at the Keyboard interrupt of MSP430F1611

    The following code I have written for that.
     "

     

    /*============================================================================*/
    #pragma vector=PORT1_VECTOR
    __interrupt void port1_isr(void)
    {
     _BIC_SR_IRQ(LPM3_bits);                 // Clear LPM3 bits from 0(SR)
      P1IE &= ~0x07;

     if(P1IFG & 0x01)  
     Start OnlineTx();
     

     if(P1IFG & 0x02)   
    Start Record();
     

     if(P1IFG & 0x04)   
     stop();

     

     P1IE |= 0x07;
     return;
    }
    /*============================================================================*/


    "

    There are three KBIs' i'm using in my application called sw1,sw2,sw4
    And I'm putting the breakpoint at the sw2. to debugg the code .

    whenever I press the sw2 , interrupt is coming at the sw2 part  and not calling the function  Start Record();

    and interrupt is keep on coming though I cleared the interrupt . and I'm pressing key only once and also checked that key releasing properly (there is contact after key is released).

    kindly help me to solve this .

     

    regards

    chethan


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