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by Burngate
Tue Sep 25, 2018 5:46 pm
Forum: Off topic discussion
Topic: Speaker Wattage and Resistance Questions
Replies: 1
Views: 22

Re: Speaker Wattage and Resistance Questions

If the amplifier driving it is designed for no less than 8 ohms, then it may well die if you connect a 2 ohm speaker.
If the amplifier doesn't die, then it may well kill the speaker.
by Burngate
Tue Sep 25, 2018 8:57 am
Forum: Troubleshooting
Topic: [Solved] 3B+ GPIO Sourcing Current while Unbooted
Replies: 6
Views: 150

Re: [Solved] 3B+ GPIO Sourcing Current while Unbooted

Glad you found the answer, and that the answer makes sense - restores one's faith in one's understanding of the real world.
Thanks for getting back to us.
by Burngate
Mon Sep 24, 2018 8:06 am
Forum: Troubleshooting
Topic: Raspberry pi Run pin wiring
Replies: 8
Views: 422

Re: Raspberry pi Run pin wiring

We don't know either the size of a pulse or its length required to reset the chip, so this is all a bit hand-waving. Since it's pulled up to 3v3 by a 10k resistor, you could try adding another pull-up resistor, say 1k, again to 3v3. That would mean extra energy would be required by any stray EMF to ...
by Burngate
Sun Sep 23, 2018 12:05 pm
Forum: Troubleshooting
Topic: The USB power appeal
Replies: 43
Views: 1240

Re: The USB power appeal

... I know what I am doing. I have done many tests to eliminate my fault before posting here. Could you answer my question? If I had the device in front of me, I'd be able to -fault-find myself; as it is I have to rely on you performing the tests. So measuring around the chip, shorting it out, etc....
by Burngate
Sun Sep 23, 2018 8:41 am
Forum: Add-ons
Topic: The 5V GPIO Power Question
Replies: 11
Views: 319

Re: The 5V GPIO Power Question

Yes, it would be nice. I think those in charge understand that. I don't think it'll happen, though
by Burngate
Sat Sep 22, 2018 5:46 pm
Forum: Troubleshooting
Topic: [Solved] 3B+ GPIO Sourcing Current while Unbooted
Replies: 6
Views: 150

Re: 3B+ GPIO Sourcing Current while Unbooted

LED0, GPIO 10 (SPI_MOSI), pin 19, low after shut-down LED1, GPIO 24, pin 18, dim after shut-down using GPIO 09 (SPI_MISO), pin 21, low after shut-down Of interest: GPIO 24 is nothing special. It should be pulled low by default, with the internal pull-down being ~50k Even if that had been altered so ...
by Burngate
Sat Sep 22, 2018 5:26 pm
Forum: Troubleshooting
Topic: The USB power appeal
Replies: 43
Views: 1240

Re: The USB power appeal

I've been keeping clear of this thread, so far, in part because others have said what I would have said. But having again read through the whole thread, these are my thoughts. So, some of your Pis - not 3B+, by the look of it - have died under similar circumstances. But they haven't actually died - ...
by Burngate
Sat Sep 22, 2018 8:31 am
Forum: Add-ons
Topic: The 5V GPIO Power Question
Replies: 11
Views: 319

Re: The 5V GPIO Power Question

I was under the impression that, to fit the extra ARM cores on the chip, they removed the power supply bits.
Looking at the Compute Module schematics, 5v doesn't appear to reach the module, so the chip can't require it.
by Burngate
Fri Sep 21, 2018 9:17 am
Forum: Beginners
Topic: Audio Jack Output Capabilities
Replies: 6
Views: 141

Re: Audio Jack Output Capabilities

The schematics of the latest Pis are available at https://www.raspberrypi.org/documentation/hardware/raspberrypi/schematics/README.md From there, it's relatively easy to calculate both output impedance and p-p drive capability For the 3B & 3B+ it's theoretically 1v p-p from 68Ω For the 2B it's 1v25 ...
by Burngate
Wed Sep 19, 2018 8:25 am
Forum: General discussion
Topic: Power led not on?
Replies: 6
Views: 166

Re: Power led not on?

Red LED off, but no lightning bolt?
Is it a 3B+ (you don't say)? What OS? Is it up-to-date?

The red LED moved from one GPIO to another on the 3B+, and the under-voltage detection circuit moved from directly driving the LED
If you're not running up-to-date Raspbian, this may be the cause.
by Burngate
Tue Sep 18, 2018 5:04 pm
Forum: General discussion
Topic: Pi 3 b + reset button
Replies: 1
Views: 78

Re: Pi 3 b + reset button

J2 pin header: on the 3B+ the hole next to the RUN hole is no longer ground - it's now Global_En for the power chip.

So just use any convenient ground point instead.
by Burngate
Mon Sep 17, 2018 6:11 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: GPIO Output Characteristics
Replies: 8
Views: 224

Re: GPIO Output Characteristics

Somewhere is a PDF - BCM2835 ARM Peripherals - and also in-depth discussion about the GPIO characteristics, by Gert and others. Nowhere does it mention open-drain or similar - unless I missed it - and I made the assumption that the I2C system drives it low for 0 and puts it into input for a 1. Yey o...
by Burngate
Mon Sep 17, 2018 5:55 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: GPIO Output Characteristics
Replies: 8
Views: 224

Re: GPIO Output Characteristics

GPIO2 & GPIO3, header pins 3 & 5, 1k8 to 3v3
GPIO-B+.png
GPIO-B+.png (21.85 KiB) Viewed 178 times
grabbed from the schematic, coloured by me; and if you look carefully there's marking to indicate those that have internal pull-ups on boot-up (the rest are pull-down)
by Burngate
Sun Sep 16, 2018 9:24 am
Forum: Beginners
Topic: Illuminated push button
Replies: 41
Views: 798

Re: Illuminated push button

If it were me, and if they're really that cheap, I'd be buying more than one, then tearing one apart to find out what's really inside.
But that's just me.
by Burngate
Sat Sep 15, 2018 6:03 pm
Forum: Beginners
Topic: Powering a sensor using an external power supply board
Replies: 2
Views: 82

Re: Powering a sensor using an external power supply board

Just to be pedantic, with 1k and 2k resistors and 5v going in, the output will be 2/3 of 5v which is 3.33333.....v
But I bet your 2k resistor is 2k2, since that's a preferred value, so it'll turn out you're getting about 3.44v (5 * 2.2 / 3.2)
Still okay, though.
by Burngate
Sat Sep 15, 2018 7:46 am
Forum: General discussion
Topic: any way to fix the microSD card reader on the P3b+?
Replies: 10
Views: 335

Re: any way to fix the microSD card reader on the P3b+?

Before you toss it, it might be worth looking in the card slot for physical damage - bent pins, &c.
by Burngate
Sat Sep 15, 2018 7:23 am
Forum: Add-ons
Topic: PoE HAT - USB Ports not working - over-current
Replies: 156
Views: 10197

Re: PoE HAT - USB Ports not working - over-current

The fault appears to be with the PoE HAT, interacting with the chip on the Pi - any PoE HAT, some Pis. So if one gets a HaT and it doesn't play ball, there's no point in getting it replaced, yet - the next HAT will be no better. We'll have to wait for the re-spin. Is that the state of affairs at the...
by Burngate
Fri Sep 14, 2018 6:29 pm
Forum: Beginners
Topic: Where is Raspberry Pi 3 B+ microSD card reader?
Replies: 9
Views: 309

Re: Where is Raspberry Pi 3 B+ microSD card reader?

There are thousands of posters who ask a question then don't come back
Maybe they're happy with the answer but just too rude to say thankyou ... when is a troll not a troll?
by Burngate
Wed Sep 12, 2018 6:41 pm
Forum: Beginners
Topic: Illuminated push button
Replies: 41
Views: 798

Re: Illuminated push button

... Also I expect a filament lamp will attempt to take more than 16 mA if connected to a GPIO. Also of interest in these circumstances: the filament will be tungsten, and the operating temperature will be in the region of 2000 C Like most substances, its resistance is temperature dependant, so at s...
by Burngate
Wed Sep 12, 2018 8:47 am
Forum: Troubleshooting
Topic: Yellow lightning bolt
Replies: 15
Views: 397

Re: Yellow lightning bolt

After a quick look, that case confuses me. It has a power button, yet the power goes directly into the Pi? Confuses me, too. And clicking on the youtube link, I discovered it's 20 minutes long. I'm not going to sit through twenty minutes of blather - if he's got something useful to say, why not wri...
by Burngate
Wed Sep 12, 2018 8:32 am
Forum: General discussion
Topic: Where to post offering Pi expertise for hire?
Replies: 4
Views: 171

Re: Where to post offering Pi expertise for hire?

Or, perhaps, https://www.raspberrypi.org/forums/viewforum.php?f=93 - "for sale"

It does say in the "Use of the 'Stuff for sale' forum" sticky
No businesses selling non-Pi goods or services
which to me implies a service such as Pi expertise is ok
by Burngate
Tue Sep 11, 2018 6:05 pm
Forum: Graphics, sound and multimedia
Topic: Generating Signal using headphone Jack
Replies: 2
Views: 78

Re: Generating Signal using headphone Jack

The headphone jack already has a low-pass filter, but also a high-pass filter, so it only lets through audio-frequency signals.

What frequencies are you interested in?
by Burngate
Tue Sep 11, 2018 5:50 pm
Forum: Add-ons
Topic: PoE HAT - USB Ports not working - over-current
Replies: 156
Views: 10197

Re: PoE HAT - USB Ports not working - over-current

If there's a diode, ideal or not, on the PoE HAT, then a higher voltage on the u-USB would take precedence. But higher voltage out of the PoE risks putting current back out of the u-USB Why they decided the ideal diode wasn't required, I don't know, since they intentionally put it in on the 3B and p...
by Burngate
Sat Sep 08, 2018 8:57 am
Forum: Graphics, sound and multimedia
Topic: Simple audio enhancement
Replies: 2
Views: 179

Re: Simple audio enhancement

By using gpio pins 12 and 13 with a slightly modified ( compared to stock ) LP filter , Pi audio can be somewhat improved . Not wanting to take the wind from your sails, but in what way is it improved? Which model are you talking about? The Pi 3B+ has a low-noise supply feeding the output stage, wh...

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