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by gwideman
Fri Sep 21, 2018 12:56 am
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

I'm working on building an interface to a burglar/fire alarm panel that puts out "10VDC-13.8VDC through 4K Ohms when high and Ground through 100 ohms when low", and have been searching high and low (if you see what I did there) for the above numbers. ... you will use something at least as sophistic...
by gwideman
Wed Jun 20, 2018 10:32 pm
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

As OP, I have twice acknowledged that the thread answered as much of my original question as it's going to, so its main purpose is served, and I've accepted that we won't be hearing a hysteresis spec. And thanks to jamesh for his long-suffering attention. Z80 Refugee and I agree that hysteresis mana...
by gwideman
Wed Jun 20, 2018 9:59 am
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

Is hysteresis really that difficult to measure. I sort of expected this to be a pretty standard test from a hardware viewpoint. Is there no standard testing device? Wouldn't something as simple as a digital POT allow a test? Hysteresis is easy to measure. However you would only be measuring that on...
by gwideman
Wed Jun 20, 2018 9:52 am
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

It's really quite simple .... [points answered below] > do not apply a noisy signal to an RPi input and expect reliable results. No signals, nor ground nor power are completely free of noise. > Hysteresis protects inputs from a slow monotonic transition, not a noisy one. One of the key protections ...
by gwideman
Wed Jun 20, 2018 6:11 am
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

Thanks again jamesh for getting back to us regarding the unavailability of the minimum hysteresis magnitude spec. So be it. You would not be able to determine it definitively yourselves because the best you could do is a statistical analysis of measurements of a modest number of sample units, which ...
by gwideman
Mon Jun 18, 2018 9:31 pm
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

OK, the requested data (or at least quite a bit of it), has now been published in a new CM datasheet. Thanks jamesh for letting us know, and also to whoever assembled the data for 3.3V. A very useful step forward. There is one significant missing spec, of the ones we discussed in this thread, and t...
by gwideman
Mon Apr 09, 2018 9:43 pm
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

Hippy I agree with your post, including the problem that people commonly misunderstand these specs, especially interpreting hysteresis to be the entire VIL..VIH range. One other point: That reflects how Microchip describe things in their datasheets. Perhaps you meant Broadcom under discussion here, ...
by gwideman
Mon Apr 09, 2018 6:32 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: New "gpio" config.txt command announcement
Replies: 38
Views: 11808

Re: New "gpio" config.txt command announcement

dh - Driving high (for outputs)
dl - Driving low (for outputs)

Do these options set the default output level (logic 1 = high, logic 0 = low), or do they select between the two drive strength options (16mA = high, and 8mA = low)? Thanks.
by gwideman
Mon Apr 09, 2018 12:16 am
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

I apologise. Thank you. you apparently totally ignoring a response made by me I accept that it appeared that way to you, though as I explained subsequently, I paid specific attention to the point you had written. But let's move on. I thank you for your most recent answers. A couple of points Hyster...
by gwideman
Sat Apr 07, 2018 8:43 pm
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

For one it explains why no simply ViH ViL data exist, Datasheets give an exact spec of the range of values that may be encountered across a population of components and temperature range, (outside of which range a component would be considered defective). Hysteresis just adds one line to that. Exam...
by gwideman
Sat Apr 07, 2018 12:17 pm
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

I am not sure the customer relations effect you are trying to have here, but it's a little "unusual". On a forum that's run on a purely volunteer basis (nobody gets paid for posting on here), what possible "customer relationship" are you imagining exists? You're not paying for support, 6by9 is not ...
by gwideman
Sat Apr 07, 2018 11:52 am
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

According to Gert's PADS documentation; the hysteresis control bits are in the same registers as the bits are which control drive strength. My belief was that, if it is possible to set the drive strength from within a user application under Linux or using bare metal, then it should likewise be poss...
by gwideman
Thu Apr 05, 2018 2:39 pm
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

Seeing as you can't be bothered to read what I write why should I bother writing anything? Perhaps HYSTERYSIS IS ALWAYS ENABLED BY THE FIRMWARE AND NOT CONTROLLABLE FROM LINUX is big enough. [...] Yes, I am getting fed up with this thread! I am not sure the customer relations effect you are trying ...
by gwideman
Thu Apr 05, 2018 4:35 am
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

Following up on 6by9's suggestion to look at the RPi's configuration to determine some of the default settings for the GPIOs. "Changing the Default Pin Configuration" https://www.raspberrypi.org/documentation/configuration/pin-configuration.md describes the format of the pertinent dt-blob.dts file, ...
by gwideman
Wed Apr 04, 2018 1:37 am
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

I've asked the question of those who have the hardware design specs, now I'm dropping out of this conversation because we're going in circles. I've wasted enough time on it. If your pursuit of the answers results in them being published, your time will certainly not have been wasted, and will be mu...
by gwideman
Tue Apr 03, 2018 10:15 am
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

https://www.raspberrypi.org/documentation/hardware/computemodule/RPI-CM-DATASHEET-V1_0.pdf section 6 (page 13) https://www.raspberrypi.org/documentation/hardware/computemodule/RPI-CM-DATASHEET-V1_0.pdf section 6 (page 13) That is useful but there are still important things missing; for example the ...
by gwideman
Tue Apr 03, 2018 5:50 am
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

> "use the GPIO without actually having any problems. Like, millions of people." +1 Almost every user who is just trying to add a push button is hit with the fact that the GPIO pins have a grey area of voltages where the value oscillates. It has been well documented by paulv in this forum. https://w...
by gwideman
Tue Apr 03, 2018 4:22 am
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

The GPIO are directly wired to the SoC on devices up to 3, on the 3 there is a GPIO expander for some pins, but I'm not sure what that covers. I missed this earlier. Thanks for this nugget, which increases the desirability of DC Electrical Characteristics. Also note, the SoC used was originally int...
by gwideman
Mon Apr 02, 2018 2:48 pm
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

> What I don't understand then is how when something so apparently fundamental is missing, so > many people have successfully used, and how so many have manufactured boards, that use the > GPIO without actually having any problems. Like, millions of people. The short answer to the impression you hav...
by gwideman
Mon Apr 02, 2018 12:51 pm
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

mahjongg wrote:
Mon Apr 02, 2018 12:23 pm
the idea that they would be like TTL is simply laughable
Are you aware of LVTTL, which many 3.3V logic families abide by, and whose logic levels are identical to TTL?

For example: http://www.ti.com/lit/sg/sdyu001ab/sdyu001ab.pdf page 4.
by gwideman
Mon Apr 02, 2018 12:43 pm
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

For what it's worth, yes the specs I have been describing would be essential for teaching Engineering 101. But I am not personally teaching such a class (though i do sometimes teach interest groups). My use of the phrase "Engineering 101" was to try to emphasize how fundamental and ubiquitous these ...
by gwideman
Mon Apr 02, 2018 8:52 am
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

... I know the current limits on the gpios are in one of the docs, thought it was that one. Gert provided a note on scribd (is that right?) which gave limited information about drive pads and being able to guarantee logic levels (e.g. how much could be sourced from a GPIO whilst the GPIO could main...
by gwideman
Mon Apr 02, 2018 8:48 am
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

So humour me, define what you need. I'll talk to people, we'll see what i can find. Well, I think it's fairly clearly spelled out earlier. But to recap: This thread is about getting what are called the "DC Electrical Characteristics", (and also "Absolute Maximum Ratings")for GPIOs and any other sig...
by gwideman
Mon Apr 02, 2018 7:16 am
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

In the docs section https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2835/BCM2835-ARM-Peripherals.pdf I did not see any electrical specs in that doc, did I miss something? Probably not, what specific specs are you after? If there are no electrical specs in that doc, why did you sug...
by gwideman
Sun Apr 01, 2018 10:53 pm
Forum: Advanced users
Topic: Documentation bugs: RPi2&3 GPIO electrical specs
Replies: 133
Views: 17964

Re: Documentation bugs: RPi2&3 GPIO electrical specs

jamesh wrote:
Sun Apr 01, 2018 9:46 pm
In the docs section

https://www.raspberrypi.org/documentati ... herals.pdf
I did not see any electrical specs in that doc, did I miss something?

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