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by SlowBro
Sat Jan 13, 2018 11:37 pm
Forum: Advanced users
Topic: Should I add a 50ns noise/glitch filter to the I2C interface?
Replies: 7
Views: 2023

Re: Should I add a 50ns noise/glitch filter to the I2C interface?

* How long: 1m
* Type: Shielded twisted pair, 22 gauge, 4 conductor, solid core, unknown capacitance but I estimate based on similar cables to be about 220pF.
* Have you actually observed any glitches? No, I'm in the design phase and want to get it right from the beginning.
by SlowBro
Sat Jan 13, 2018 6:47 pm
Forum: Advanced users
Topic: Should I add a 50ns noise/glitch filter to the I2C interface?
Replies: 7
Views: 2023

Re: Should I add a 50ns noise/glitch filter to the I2C interface?

joan wrote:
Sat Jan 13, 2018 9:14 am
Perhaps ask if anyone is running I2C at 400kbps or faster?
I am. Change I2C Speed with Raspberry Pi
by SlowBro
Sat Jan 13, 2018 5:54 am
Forum: Advanced users
Topic: Should I add a 50ns noise/glitch filter to the I2C interface?
Replies: 7
Views: 2023

Should I add a 50ns noise/glitch filter to the I2C interface?

Should I add a 50ns noise filter to the I2C interface on an RPi, and if so how do I do it? This document states, "The serial interface specification for high speed data transfer (400 kHz and faster) recommends a 50 ns noise filter on the inputs to prevent double-clocking and miss-communication." I a...
by SlowBro
Sat Jan 13, 2018 5:49 am
Forum: Advanced users
Topic: Zero W exceeds USB spec for input capacitance?
Replies: 9
Views: 1428

Zero W exceeds USB spec for input capacitance?

So I noticed on the Zero W schematic that C1 is a 47u cap connected directly to the USB port. Just wondering how that can be, since the USB spec calls for a maximum input capacitance of 10u ? I'm guessing you have to be careful when connecting the Zero's power port to a hub and/or standard PC socket...
by SlowBro
Mon Dec 18, 2017 10:16 am
Forum: General discussion
Topic: Raspbian with Read-only Root
Replies: 195
Views: 95280

Re: Raspbian with Read-only Root

If you make /boot read-only how will you tell the OS when you want to reboot into read-write mode for updates and such?
by SlowBro
Wed Dec 13, 2017 11:53 am
Forum: General discussion
Topic: Raspbian with Read-only Root
Replies: 195
Views: 95280

Re: Raspbian with Read-only Root

The answer to the first question is that is expected behavior. You must be able to write to /boot to alter the boot configuration to be able to change whether the system boots in read only mode or read/write.

I didn’t understand your second question.
by SlowBro
Mon Dec 11, 2017 11:22 am
Forum: Beginners
Topic: FCC certification for Pi Zero W with case
Replies: 21
Views: 3776

Re: FCC certification for Pi Zero W with case

you are still supposed to write a DoC certificate Yes, that's where I got stuck with your comments. When I hear the term "DoC" I think of the old definition which required one to use the accredited lab which costs $$$$, though still less expensive than full certification. Sounds like you're describ...
by SlowBro
Thu Dec 07, 2017 1:14 am
Forum: Beginners
Topic: FCC certification for Pi Zero W with case
Replies: 21
Views: 3776

Re: FCC certification for Pi Zero W with case

Plot twist: This year there is no more requirement for lab accreditation for DoC, which is now retired. Now there is only Supplier’s Declaration of Conformity, called SDoC. So everyone not certifying can carry out the much cheaper SDoC process. http://www.sgs.com/en/news/2017/08/safeguards-13117-us-...
by SlowBro
Thu Dec 07, 2017 12:25 am
Forum: Beginners
Topic: FCC certification for Pi Zero W with case
Replies: 21
Views: 3776

Re: FCC certification for Pi Zero W with case

I see the first assertion now, I must be blind. It lists exceptions and I want to study that further. Second assertion, "the only way you can make any changes of any kind is through the declaration of conformity process for assemblers of personal computers", I also was blind on that -- I do see the ...
by SlowBro
Wed Dec 06, 2017 12:49 pm
Forum: Beginners
Topic: FCC certification for Pi Zero W with case
Replies: 21
Views: 3776

Re: FCC certification for Pi Zero W with case

While the description of permissive changes is correct, unfortunately only the holder of the authorization can make them. I don't see that in the link you provided. Unfortunately I believe the only way you can make any changes of any kind is through the declaration of conformity process for assembl...
by SlowBro
Tue Dec 05, 2017 6:07 pm
Forum: Beginners
Topic: What is the Zero maximum total USB peripheral current draw really?
Replies: 9
Views: 907

Re: What is the Zero maximum total USB peripheral current draw really?

gordon77 wrote:
Tue Dec 05, 2017 11:51 am
Some are overcurrent protected...

https://uk.rs-online.com/web/p/plug-in- ... y/9098126/
Looks like a winner.
by SlowBro
Tue Dec 05, 2017 6:04 pm
Forum: Beginners
Topic: What is the Zero maximum total USB peripheral current draw really?
Replies: 9
Views: 907

Re: What is the Zero maximum total USB peripheral current draw really?

W. H. Heydt wrote:
Tue Dec 05, 2017 3:48 pm
Designing power supplies is not for the faint of heart.
Well I don’t need to build a power supply. I need to choose a quality supply and safeguard against over current situations.
by SlowBro
Tue Dec 05, 2017 3:35 pm
Forum: Beginners
Topic: What is the Zero maximum total USB peripheral current draw really?
Replies: 9
Views: 907

Re: What is the Zero maximum total USB peripheral current draw really?

Right but is a 2.5A supply going to halt somewhere near or above 2.5A?

I think I will just install my own resettable fuse. Is there a good reference for building power safety? A whitepaper or something.
by SlowBro
Tue Dec 05, 2017 11:07 am
Forum: Beginners
Topic: What is the Zero maximum total USB peripheral current draw really?
Replies: 9
Views: 907

Re: What is the Zero maximum total USB peripheral current draw really?

Right. Are some supplies current limited?
by SlowBro
Tue Dec 05, 2017 2:37 am
Forum: Beginners
Topic: What is the Zero maximum total USB peripheral current draw really?
Replies: 9
Views: 907

Re: What is the Zero maximum total USB peripheral current draw really?

Well I think this answers my question: No fuse, so in theory it should be able to handle all 2.5 amps. Power goes straight from the input to the output.
viewtopic.php?p=850752#p850752
by SlowBro
Tue Dec 05, 2017 2:32 am
Forum: Beginners
Topic: What is the Zero maximum total USB peripheral current draw really?
Replies: 9
Views: 907

What is the Zero maximum total USB peripheral current draw really?

I see on this FAQ that the maximum total USB peripheral current drive is “Limited by PSU, board, and connector ratings only.” So does that mean if I use a 2.5A-rated supply and similarly-rated cable I should expect to get the entire 2.5 amps minus whatever the processor is using at the time? I know ...
by SlowBro
Sat Dec 02, 2017 10:56 am
Forum: General discussion
Topic: use pi zero w in commercial production
Replies: 60
Views: 17196

Re: use pi zero w in commercial production

Matthias, contact info@raspberrypi.org, they may be able to help.
by SlowBro
Tue Nov 21, 2017 10:37 am
Forum: General discussion
Topic: FCC Certification for Pi in a Box
Replies: 24
Views: 7332

Re: FCC Certification for Pi in a Box

Anyone can just pull bits of text out of a web page, but personally if I was developing a product to sell would not ask for help in a Community Forum to get my product to market, but each to their own............. The bits of text out of a web page that I pulled directly answers the OP's question w...
by SlowBro
Tue Nov 21, 2017 10:19 am
Forum: General discussion
Topic: FCC Certification for Pi in a Box
Replies: 24
Views: 7332

Re: FCC Certification for Pi in a Box

This ia a volunteer led forum, therefore how can you rely on answers being accurate ?? You underestimate the power of volunteers :D Where volunteer forums really shine is when someone finds and shares the relevant rules and regulations directly from the horse's mouth. Such as what I did in the post...
by SlowBro
Tue Nov 21, 2017 2:57 am
Forum: General discussion
Topic: Combining Voltage From Multiple GPIO Pins?
Replies: 10
Views: 2324

Re: Combining Voltage From Multiple GPIO Pins?

You can light a white/blue LED from 3.3v or lower using a fun little circuit called a "Joule Thief". https://en.wikipedia.org/wiki/Joule_thief OP said that the LED uses 35mA... I don't see how that could be successful with voltage doublers, capacitors, Joule Thiefs, etc. As I understand their opera...
by SlowBro
Tue Nov 21, 2017 2:13 am
Forum: Beginners
Topic: FCC certification for Pi Zero W with case
Replies: 21
Views: 3776

Re: FCC certification for Pi Zero W with case

Aha, I think I found the answer to OP's and my question here . B. A certified transmitter not approved as a modular device under the FCC rules may be placed or inserted into another host as either a stand-alone or plug-in transmitter, if it is accessible by the enduser or field technician and the FC...
by SlowBro
Tue Nov 21, 2017 1:29 am
Forum: Beginners
Topic: FCC certification for Pi Zero W with case
Replies: 21
Views: 3776

Re: FCC certification for Pi Zero W with case

Actually on the first, yes anything that is manufactured is on file with the FCC. The part about filing isn't completely true and I want to correct this for the benefit of other beginners. Many items indeed must be on file but some products do not require anything to be on file with the FCC if they...
by SlowBro
Mon Nov 20, 2017 11:49 pm
Forum: General discussion
Topic: FCC Certification for Pi in a Box
Replies: 24
Views: 7332

Re: FCC Certification for Pi in a Box

Anyone know if using a USB dongle with an A+ requires recertification? Found the answer on the FCC website . I wonder if this also applies to the onboard Wi-Fi on RPi3 and 0W devices? Edit: A slightly different set of rules apply to devices with onboard Wi-Fi . That post should answer OP’s question...
by SlowBro
Mon Nov 20, 2017 10:55 pm
Forum: General discussion
Topic: FCC Certification for Pi in a Box
Replies: 24
Views: 7332

Re: FCC Certification for Pi in a Box

Already contacted them, waiting for a response. Are you saying they're the only ones who can answer this question?
by SlowBro
Mon Nov 20, 2017 9:11 pm
Forum: General discussion
Topic: FCC Certification for Pi in a Box
Replies: 24
Views: 7332

Re: FCC Certification for Pi in a Box

There is an exception. Admittedly, I'm not very familiar with the specifics of this exception, but I know a little bit. If the component has a special FCC certification in which is is classified as a modular component, then it can be put in products without the need of recertification. Most of the ...

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