[sclug] thermometer accessory for my raspberry pi

[Neil Haughton]

Some guidance on suitable values here:

http://en.wikipedia.org/wiki/Pull-up_resistor

HTH

Neil.

On 9 August 2012 13:00, <sclug-request at sclug.org.uk> wrote:

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> Today's Topics:
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>    1. thermometer accessory for my raspberry pi (Chris Couzens)
>    2. Re: thermometer accessory for my raspberry pi (Sean Furey)
>
>
> ---------- Forwarded message ----------
> From: Chris Couzens <ccouzens at gmail.com>
> To: sclug at sclug.org.uk
> Cc:
> Date: Thu, 9 Aug 2012 08:40:03 +0100
> Subject: [sclug] thermometer accessory for my raspberry pi
> Hi,
>
> A couple of you were asking about the thermometer I couldn't get working
> with my Raspberry Pi.
>
> Here is the spec sheet.
>
> http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Sensors/Weather/RHT03.pdf
>
> If you're wondering what the GPIO (General Purpose Input Output) API is
> like for the Raspberry Pi (and other Linux computers), here is the code to
> my Raspberry Pi single digit display.
>
> https://github.com/ccouzens/raspberry_pi_led
>
> Chris Couzens
>
>
> ---------- Forwarded message ----------
> From: Sean Furey <sean-lists-sclug at furey.me.uk>
> To: sclug at sclug.org.uk
> Cc:
> Date: Thu, 9 Aug 2012 12:21:01 +0100
> Subject: Re: [sclug] thermometer accessory for my raspberry pi
> While it doesn't explicitly mention a pull-up resistor, I'm fairly
> certain it will need one.  It's been a while since I've done any of
> this, but hopefully someone will correct me if I've misremembered any
> of it...
>
> Attach one end of a largish resistor to the signal line between the
> device and GPIO.  I'm being deliberately vague about "largish", 1MOhm
> springs to mind as a reasonable value, maybe someone else can confirm?
>
> When actually using this from the Pi side, never output a '1'.  If you
> want the line to be high, configure the GPIO pin as an input, the
> resistor will pull it up.  If you want it low, configure it as an
> output, setting it to '0'.
>
> Timing might be fun for this, as I think you're going to need to be
> polling quite rapidly to measure the lengths of pulse to distinguish
> '1' vs '0' from the device.  If you're looking at other peripherals to
> wire up, I2C is somewhat easier here, as the master (Pi in this case)
> supplies the clock, so it can go at whatever speed works for you.
>
> *waits for laughter from someone who actually works on electronics*
>
> Sean
>
> On Thu, Aug 09, 2012 at 08:40:03AM +0100, Chris Couzens wrote:
> > Hi,
> >
> > A couple of you were asking about the thermometer I couldn't get working
> with my Raspberry Pi.
> >
> > Here is the spec sheet.
> >
> > http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Sensors/Weather/RHT03.pdf
> >
> > If you're wondering what the GPIO (General Purpose Input Output) API is
> like for the Raspberry Pi (and other Linux computers), here is the code to
> my Raspberry Pi single digit display.
> >
> > https://github.com/ccouzens/raspberry_pi_led
> >
> > Chris Couzens
>
>
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