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by jbeale
Thu Dec 12, 2019 3:40 pm
Forum: Troubleshooting
Topic: Pi 4 4GB- Wifi not working when resolution is set too high
Replies: 74
Views: 5115

Re: Pi 4 4GB- Wifi not working when resolution is set too high

"...just touching the insulation of the microHDMI to HDMI adapter cable at the wrong position stopped the ping reaching router." at least in that case, it is clearly RF energy coming off the cable and interfering with wifi. If you put a noise source (leaky cable) right next to your onboard wifi ante...
by jbeale
Tue Dec 10, 2019 11:07 pm
Forum: General discussion
Topic: audio for time sync idea
Replies: 7
Views: 235

Re: audio for time sync idea

I recently found two apps, one for Android and one for iOS, that kind of does what you are talking about called WWVB Emulator (Android) and Clock Wave (iOS). They are designed to use the magnet a speaker attached to your phone to create a time signal to set a radio controlled clock directly. I am c...
by jbeale
Sun Dec 08, 2019 5:39 am
Forum: Python
Topic: GPIO input interrupt: minimizing jitter & delay
Replies: 17
Views: 4613

Re: GPIO input interrupt: minimizing jitter & delay

That was a few years ago, but I think it was a PPS signal from a GPS receiver. I think over a week, the main factor influencing frequency is temperature (assuming the circuit loading, voltage input etc. remain constant). So if the ambient temperature stays within fixed limits, so does the frequency....
by jbeale
Sat Dec 07, 2019 9:51 pm
Forum: Advanced users
Topic: PPS input signal: can there be more than one?
Replies: 2
Views: 128

Re: PPS input signal: can there be more than one?

In case of interest, here is some data comparing the difference in PPS timestamps over about 30 minutes from a free-running VCXO clock (PPS0) with a GPSDO signal (PPS1). Taking the difference gets rid of the long-term wander of the Pi's own internal clock. Due to the usual Linux OS latencies, you ca...
by jbeale
Sat Dec 07, 2019 5:27 pm
Forum: Advanced users
Topic: PPS input signal: can there be more than one?
Replies: 2
Views: 128

Re: PPS input signal: can there be more than one?

Oops, missed this note. Apparently a capability for multiple PPS signals was added in 2018. Thanks for adding this useful capability! https://github.com/raspberrypi/linux/issues/2352 ...sure enough it is working, just by adding another line in /boot/config.txt: # enable GPS PPS dtoverlay=pps-gpio,gp...
by jbeale
Sat Dec 07, 2019 5:14 pm
Forum: Advanced users
Topic: PPS input signal: can there be more than one?
Replies: 2
Views: 128

PPS input signal: can there be more than one?

I'm curious if it is possible to have more than one PPS signal attached to the same Raspberry Pi. Following the guide at http://www.unixwiz.net/techtips/raspberry-pi3-gps-time.html I have edited /boot/config.txt to include: # enable GPS PPS dtoverlay=pps-gpio,gpiopin=4 then 'dmesg' reports lines lik...
by jbeale
Fri Dec 06, 2019 9:36 pm
Forum: HATs and other add-ons
Topic: RPi + PS3Eye getting Sound-microphone
Replies: 20
Views: 19738

Re: RPi + PS3Eye getting Sound-microphone

I just got a Pi4. I can confirm the same commands as in my last post work the same way with the PS3-Eye camera sound input on the Pi4, as they did on the Pi3B. pi@rp40:~ $ uname -a Linux rp40 4.19.75-v7l+ #1270 SMP Tue Sep 24 18:51:41 BST 2019 armv7l GNU/Linux pi@rp40:~ $ cat /sys/firmware/devicetre...
by jbeale
Tue Dec 03, 2019 6:51 pm
Forum: HATs and other add-ons
Topic: RPi + PS3Eye getting Sound-microphone
Replies: 20
Views: 19738

Re: RPi + PS3Eye getting Sound-microphone

Note to self: the below "arecord" command works with PS3 Eye device on a recent version of Raspbian, on Pi 3B. This records 4 channel audio at 48kHz, 16 bits. I verified that all 4 channels work as expected, and the time of arrival of a sharp noise is delayed on the more distant mics by ( distance /...
by jbeale
Mon Dec 02, 2019 8:16 pm
Forum: General discussion
Topic: audio for time sync idea
Replies: 7
Views: 235

Re: audio for time sync idea

I did this quick C / PiGPIO hack to generate a 2 kHz burst at the top of each second, per local system time: https://github.com/jbeale1/DataAcq/blob/master/PPS-Pi-GPIO.c At the moment, comparing this GPIO output signal with my GPSDO shows my Pi's clock is within 1 msec of UTC. It's NTP is unaware of...
by jbeale
Sun Dec 01, 2019 10:34 pm
Forum: General discussion
Topic: audio for time sync idea
Replies: 7
Views: 235

Re: audio for time sync idea

At this point, something like LTC or at least a 1pps signal as another audio channel seems to be the only way to be sure. In case of interest, I am recording audio from a RPi using this command: ffmpeg -nostdin -loglevel quiet -f alsa -ac 2 -ar 22050 -i plughw:"1" -map 0:0 -c:a flac \ -f segment -st...
by jbeale
Sun Dec 01, 2019 9:21 pm
Forum: General discussion
Topic: audio for time sync idea
Replies: 7
Views: 235

Re: audio for time sync idea

I do have a GPSDO unit with a precise 1-PPS output, I was just trying to avoid some effort to turn that into an audible toneburst. I tried an Android app called "Smart Time Sync" that does have a simple beep-per-second option, but comparing its audio output with the 1-PPS on my scope, I see that its...
by jbeale
Sun Dec 01, 2019 8:28 pm
Forum: General discussion
Topic: audio for time sync idea
Replies: 7
Views: 235

audio for time sync idea

I have a Pi working as a continuous audio recorder, and I'd like to check how accurately my audio file timestamps line up with official UTC time. I don't have reliable radio reception of the NIST time signal service here (WWV, WWVH) and my VoIP phone line seems to have a lot of delay listening to th...
by jbeale
Sun Dec 01, 2019 6:01 am
Forum: Advanced users
Topic: ntp accuracy vs Pi model ?
Replies: 5
Views: 322

Re: ntp accuracy vs Pi model ?

Another update, here are the two R-Pi devices. What I was calling "Pi #1" is named rp02 (at 192.168.1.70) and "Pi #2" is named rp19. From the viewpoint of rp19, the rp02 device on the same LAN at 192.168.1.70 is Stratum 2, and has the overall lowest delay, offset, and jitter, and yet is for some rea...
by jbeale
Sun Dec 01, 2019 3:35 am
Forum: Advanced users
Topic: ntp accuracy vs Pi model ?
Replies: 5
Views: 322

Re: ntp accuracy vs Pi model ?

I need to amend my initial post- after returning to the situation some hours later I see now the second Pi reports itself to be only about 0.5 msec different from the first Pi. I think I looked too quickly after a reboot and the clock had not yet settled down into the best alignment. I had not reali...
by jbeale
Sat Nov 30, 2019 3:25 pm
Forum: Advanced users
Topic: ntp accuracy vs Pi model ?
Replies: 5
Views: 322

Re: ntp accuracy vs Pi model ?

I'm after the best accuracy I can get (measuring time-of-arrival of sound waves at different Pi units, hopefully to the millisecond). At first I thought it was all network delays just as you say. However in my test with two R-Pi's, where Pi#1 is used as a normal NTP client relying on external source...
by jbeale
Sat Nov 30, 2019 3:08 pm
Forum: Graphics, sound and multimedia
Topic: [Question] 8 HD screens on Rapsberry pi 4
Replies: 8
Views: 388

Re: [Question] 8 HD screens on Rapsberry pi 4

...although the official line has always been, and still remains, that the Pi Zero is sold one (1) per customer.
by jbeale
Sat Nov 30, 2019 2:12 am
Forum: Advanced users
Topic: ntp accuracy vs Pi model ?
Replies: 5
Views: 322

ntp accuracy vs Pi model ?

If I wanted to use some Pi board as an NTP server, would it be correct to assume the best accuracy would be possible using the Pi 4? I understand that the Pi4 has the fastest CPU and the largest throughput as it has a true 1Gbit ethernet port. I'm just not sure if total latency is necessarily lower,...
by jbeale
Fri Nov 29, 2019 4:04 pm
Forum: Graphics, sound and multimedia
Topic: [Question] 8 HD screens on Rapsberry pi 4
Replies: 8
Views: 388

Re: [Question] 8 HD screens on Rapsberry pi 4

Here's an example of a 2x2 HDMI "video wall processor" (Takes 1 Video Input and Splits it into 4 Video Ouputs for 4 Displays). It costs $450 https://www.amazon.com/Video-Processor-Version-Controller-Splitter/dp/B077KZ93C8 Compare that with the price of a Pi, and it looks to me like the easiest solut...
by jbeale
Wed Nov 20, 2019 3:18 pm
Forum: Device Tree
Topic: GPIO 1sec High at Boot and Poweroff How to?
Replies: 7
Views: 410

Re: GPIO 1sec High at Boot and Poweroff How to?

^ this post on loading order feels like important information that should be documented somewhere easier to find than here, if it isn't already.
by jbeale
Tue Nov 12, 2019 8:12 pm
Forum: Networking and servers
Topic: USB over IP for Raspberry Pi
Replies: 7
Views: 307

Re: USB over IP for Raspberry Pi

"I need to remotely control a computer that I do not have admin rights to" Yes. In addition to possible legit needs, that is every hacker's mission statement, and I'm pretty sure this has been done; for example hiding the PiZero inside a normal mouse or other USB device, then tricking your target in...
by jbeale
Thu Oct 31, 2019 7:28 pm
Forum: General discussion
Topic: USB audio adapter that also amplifies sound?
Replies: 4
Views: 315

Re: USB audio adapter that also amplifies sound?

AFAIK there is no standard for "headphone level" but the USB audio adaptors I've used have been loud enough for me, when the digital volume control (ALSA level control) is turned up. Headphones usually have low impedance (8 to 32 ohms) and will not give much volume if driven directly from a relative...
by jbeale
Wed Oct 30, 2019 9:20 pm
Forum: Beginners
Topic: Path to pressure sensors
Replies: 4
Views: 335

Re: Path to pressure sensors

If you want to measure impact force over a small target area, that's doable with a force or acceleration sensor connected to a rigid plate. This is the same idea as a bathroom scale, and has similar requirements ( you have to be careful about the support structure, and how loads in different directi...
by jbeale
Wed Oct 30, 2019 9:06 pm
Forum: Networking and servers
Topic: communication between Raspis over 60GHz band
Replies: 9
Views: 668

Re: communication between Raspis over 60GHz band

I didn't even realize that 60 GHz is now generally available. From https://en.wikipedia.org/wiki/IEEE_802.11ad and https://arstechnica.com/gadgets/2016/12/802-11ad-wifi-guide-review/ I see that the range of this mode is up to 10 meters in open air, but it will not go through a single interior wall a...
by jbeale
Sun Oct 27, 2019 1:53 am
Forum: Camera board
Topic: PiKrellCam: motion vector detect + OSD web interface
Replies: 1484
Views: 347742

a PiKrellCam wildlife capture

In case of interest, here's a wildlife moment in my backyard that would have passed by unnoticed, except for PiKrellCam.
This was yesterday around lunchtime. I can't quite tell what's for lunch here, though I know there are (were?) wild turkey about.
https://youtu.be/gLMD1DlPo8s
by jbeale
Fri Oct 18, 2019 7:49 pm
Forum: Raspbian
Topic: uptimed shows negative times
Replies: 5
Views: 724

Re: uptimed shows negative times

The RPi does not come with a hardware RTC. If you start logging information before the network is up and the system clock is set from a network source, then the time/date information will have continued from whenever the Pi was last shut down, instead of the current time at boot. That should produce...

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