Ordinary 5% resistors will work fine. Probably anything from 1k to 100k
would work. Most likely you have a loose connection somewhere. Did you
try running the bus at a lower speed? If your wiring is long (> 10cm)
it may be better to run it slower.
Martin
On 2013-04-29 17:44, Julian Brooks 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.pe...@sympatico.ca
<mailto:martin.pe...@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.pe...@sympatico.ca
<mailto:martin.pe...@sympatico.ca>
<mailto:martin.peach@__sympatico.ca
<mailto:martin.pe...@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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