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Olivierp

Member since Jan 2014 • Last active Mar 2014
  • 2 conversations
  • 9 comments

Most recent activity

    • 5 comments
    • 3,966 views
  • in General
    Avatar for Olivierp

    It works. I found out how a "pulldown resistor" would solve the noise problem, and a with a bit of testing I was able to generate the 40khz pwm and record it in a 4096 bytes waveform at 20khz.
    Here is a photo of the nokia LCD on which I visualize the result.
    The Chirp duration was 100ms, during which 4 spikes were recorded.
    I will try to record the signal with my raspberrypi, maybe it can handle a higher frequency.

    Now one of the issue I have left is the 3.3V. Is there a way - of course with an external source of power - to have the 40khz PWM at twice or thrice the voltage?

    With some googling I found circuits such as:
    MAX756 or LT1073

    The MAX757 spec specifies an "Oper. Freq." of 500kHz. Does this mean that If I provide it with a 40khz PWMed 3.3V from the espruino it will deliver a 40khz square signal at 5.0V ?

  • in General
    Avatar for Olivierp

    Thank you very much for these explanations.
    I am trying to make it chirp then!

  • in General
    Avatar for Olivierp

    I have bought a couple "C7210" ultrasound emitter / receiver.
    The emitter needs a 40khz pulse, and I would like to analyze the echoed signal on the receiver.
    I tried to proceed like this:
    C9 => Emitter
    C5 => Receiver

    ( the second pin of emitter and receiver is to GND ).

    // wout is the waveform I want to send to the emitter
    var wout = new Waveform(256);
    for (var i=0;i<256;i++) wout.buffer[i] = 128+Math.sin(i*Math.PI/128)*127;
    
    // win is the waveform I want to record from the receiver
    var win = new Waveform(512);
    win.on("finish", function(buf) {
       drawBuffer(buf); // ( I have a small lcd on which I draw the waveform )
       win.startInput(C5,40000,{repeat:false});­ // I want to record the next 512 bytes
    });
    
    C9.reset();
    C5.reset();
    // How do I output a 40khz waveform ?
    analogWrite(C9,0.5,{ freq:40000}); // pwm at 40khz ?
    wout.startOutput(C9, 4000, { repeat:true }); // modulates the pwm ?
    
    // How do I record an analog signal on a pin?
    win.startInput(C5,40000,{repeat:false});­
    

    Also I am not sure if the 3.3V of the esperuino are enough to make the ultrasound emitter.

    So far it looks like I've recorded only parasites. Can the espruino generate and record a 40khz signal? Am I missing something?

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  • in Interfacing
    Avatar for Olivierp

    I am quite amazed: the ideal module would be the "GSM2 click", as used by @Hardware_Hacks , but the module costs 45€, more than twice the price of a full-blown gsm phone.

    I just fall on this:
    http://hackaday.com/2010/10/18/cheap-and­-easy-sms-via-gsm-for-your-mcu/

    It looks possible to do the trick via some USB dongle.
    If anyone already had a success this way, please share!

  • in General
    Avatar for Olivierp

    Ok, at the end of the day I found out that my breadcrumb did not work as I expected: the power lines at the top and bottom were not propagated along the whole length.

  • in Interfacing
    Avatar for Olivierp

    Hi,
    I would like to connect a SIM card to my espruino and dial it with a BAYES protocol.
    The primary goal is to send/receive SMS messages.
    Can anyone suggest a chipset which would do the job?

  • in General
    Avatar for Olivierp

    Thank you for your answer.
    I am a complete newbie. Can you just confirm:
    Can I connect a battery ( in my case 4 AA batteries daisy-chained ) to VBAT / GND ?
    Can I connect the batteries to VBAT/GND while USB is connected to my PC ?
    I would rather not toast my board too quickly. Thanks for your help.

  • in General
    Avatar for Olivierp

    Yes, the "-" of the batteries is connected to the GND of the board and the marron wire of the servos is on the same line.

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