[PD] Sensors GPIO Raspberry Pi Pd

[Julian Brooks]

BTW
This is the multiplexer:
http://uk.farnell.com/jsp/search/productdetail.jsp?sku=1106109
and the housing:
http://uk.farnell.com/jsp/search/productdetail.jsp?sku=1103846

Think these are right?


On 29 April 2013 22:44, Julian Brooks <jbeezez at gmail.com> wrote:

> Hi Martin / all,
>
> Possibly overly-nerdy question here:
>
> I'm buying the various bits and pieces we require for the multiplexer and
> I'm noticing quite a difference in pricing options for the pull-up
> resistors.
> There's this one:
> http://uk.farnell.com/welwyn/rc55-10k-0-1/resistor-10k-250mw-0-1/dp/9499938
> which is 86p each.
> Or there's something like this:
>
> http://uk.farnell.com/multicomp/mcf-0-25w-10k/resistor-10k-250mw-5/dp/9339060
> which is 2p each.
>
> The former's spec sheet talks about its very low noise ratio and thinking
> on from reading the sensors spec sheet it's also pushed there to use
> low-noise components.
>
> Do you think it actually makes any difference?  I have to buy a minimum 50
> of the cheap ones so buying a couple of the dearer ones doesn't actually
> make much of a difference.
>
> It got me thinking as you mentioned that your getting virtually no PEC
> errors from the sensors whereas as we are getting them very regularly.  I
> had been thinking it was the soldering of those pernickety sensors but
> could it also be the cheap 4k resistors currently on our board?
>
> Cheers,
>
> Julian
>
>
> On 29 April 2013 16:38, Martin Peach <martin.peach at sympatico.ca> wrote:
>
>> Here's a patch to display data from two D6T sensors on the same I2C bus.
>> The clock line is switched using a 4051 analog multiplexer. The control
>> line is GPIO_17 of the Pi connected to A of the 4051 (B, C and Inhibit are
>> at 0V). 10k resistors to 3.3V are on each sensor's clock line at X0 and X1
>> of the 4051 (I2C clock connects to X). Because the code accesses the GPIO
>> file system it needs to be run as root. I have two different sensors so the
>> code reads two different packet lengths. Just a proof of concept, there
>> could be up to 8 identical sensors on the same bus with this setup.
>>
>> Martin
>>
>>
>> On 2013-04-25 20:04, Julian Brooks wrote:
>>
>>> Just spotted this:
>>> https://github.com/kadamski/**i2c-gpio-param<https://github.com/kadamski/i2c-gpio-param>
>>> Could be useful
>>>
>>>
>>> On 25 April 2013 15:54, Martin Peach <martin.peach at sympatico.ca
>>> <mailto:martin.peach@**sympatico.ca <martin.peach at sympatico.ca>>> wrote:
>>>
>>>     On 2013-04-25 10:37, Julian Brooks wrote:
>>>
>>>         'Nother 2 dumb questions:
>>>         What's the difference between the ones that have
>>>         spider/centipede type
>>>         legs and the straight ones (which would be best to get).
>>>
>>>
>>>     The PDIP package is what you want, not the SOIC. The only difference
>>>     is size. DIP packages are human-friendly, surface mount is for
>>> robots.
>>>
>>>
>>>         And also are you attaching the MC14051 to any type of
>>>         board/adaptor or
>>>         just soldering straight on to the pins?
>>>
>>>
>>>     I have it in a breadboard right now, to make it more permanent I
>>>     would solder a socket to a prototyping board then (after verifying
>>>     the connections) plug the chip into the socket. Soldering to the
>>>     pins makes it difficult to replace the IC, and risks damaging it
>>>     with the heat if you're not good at soldering quickly and to the
>>>     point. A CD4051 would also work, it's basically the same circuit.
>>>
>>>     Martin
>>>
>>>
>>>
>>>
>>
>
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