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by TimG
Sat Feb 15, 2020 4:45 pm
Forum: General discussion
Topic: STRANGE -- make changes - reboot - changes are gone!???
Replies: 10
Views: 302

Re: STRANGE -- make changes - reboot - changes are gone!???

Here's a little script that my Pis run daily. It tests the filesystem, looks for kernel errors, and sends a warning email if anything is wrong. #!/bin/bash # email parameters email="sendEmail -f [email protected].com -t [email protected].com -s smtp.mail.com:587 -o tls=yes -xu username -xp password -q" subj="Error from...
by TimG
Sat Feb 15, 2020 3:30 pm
Forum: General discussion
Topic: STRANGE -- make changes - reboot - changes are gone!???
Replies: 10
Views: 302

Re: STRANGE -- make changes - reboot - changes are gone!???

Did you toggle read-only mode in the rpi config program or another way? Another possibility is that the SD card is damaged and has turned read-only. I’ve had a couple of memory cards do this after a power brown-out. It’s not immediately obvious because no errors are generated, and as long as the ne...
by TimG
Tue Jan 14, 2020 9:58 pm
Forum: General discussion
Topic: Future of raspberry pi - software related
Replies: 382
Views: 22823

Re: Future of raspberry pi

Remember, I said software work, not hardware. Hardware requests just get into a mess, but it would be interesting to know where people think the software needs work. It would be fantastic to see somebody pick up development of the WiringPi library. Of all the various GPIO libraries, WiringPi was es...
by TimG
Fri Nov 22, 2019 9:35 pm
Forum: Raspbian
Topic: Readonly Root with OverlyFS
Replies: 45
Views: 20491

Re: Readonly Root with OverlyFS

[...] And that's it. You are executing things on a rw version of the root, so you can apt update & upgrade normally You can receive some warnings about unable to communicate with systemd, but I found that are normally non fatal. This is great! I haven't tried it yet, but I certainly will soon. Do y...
by TimG
Mon Oct 28, 2019 2:00 pm
Forum: General discussion
Topic: What does it take for the Pi 4B to reach 3A power consumption?
Replies: 7
Views: 822

Re: What does it take for the Pi 4B to reach 3A power consumption?

Your meter doesn't show you the very short (millisseconds) current peaks that may happen. Absolutely. When I measured a Pi2 it drew a 1 millisecond current spike of 700mA during boot. USB peripherals may do the same. These load spikes can cause cumulative damage to power supplies. Some supplies hav...
by TimG
Sun Oct 20, 2019 11:33 am
Forum: General discussion
Topic: Battery Level Indicator -- While Charging
Replies: 17
Views: 1388

Re: Battery Level Indicator -- While Charging

Most LiPo chargers have a charging status indicator. It won’t tell you what the charge level is, only when charging is complete. The detection is done by voltage levels: as the cell approaches it’s maximum voltage the charging current is reduced and then stopped at around 4.2V. More sophisticated ch...
by TimG
Fri Oct 11, 2019 2:07 am
Forum: General discussion
Topic: How can I monitor power supplied to my Pi 4B?
Replies: 15
Views: 803

Re: How can I monitor power supplied to my Pi 4B?

This works well and monitors both current and voltage: https://www.adafruit.com/product/904 With earlier Pis I desoldered the main polyfuse and used the pads to wire in the INA219 board. It looks to me as though the Pi4 can’t be modified in this way, so the monitor circuit needs to be spliced into t...
by TimG
Mon Oct 07, 2019 12:21 pm
Forum: General discussion
Topic: Real time data acquisition and graphing using arduino and Raspberry pi
Replies: 7
Views: 388

Re: Real time data acquisition and graphing using arduino and Raspberry pi

There are 3 parts to this: Electronic interface: Do you have something already which can read out mains AC? Data acquisition: It sounds like you’re trying to get the phase relationship between current and voltage, so a fairly high sampling frequency will be needed. Something like this might be suita...
by TimG
Tue Sep 24, 2019 8:29 am
Forum: Troubleshooting
Topic: PIR motion sensor always outputting
Replies: 1
Views: 98

Re: PIR motion sensor always outputting

Daniel, can you post a clear and well-lit photo of your wiring, and a link to the datasheet of your PIR sensor?
Is the false detection literally continuous, or just frequent?
by TimG
Mon Sep 16, 2019 11:58 pm
Forum: Troubleshooting
Topic: sshfs causes pcmanfm to go berserk
Replies: 0
Views: 113

sshfs causes pcmanfm to go berserk

It seems that any failed sshfs connection, with a mount-point inside the user's home directory, will cause pcmanfm to go berserk and load the CPU 100% Steps to reproduce with latest Raspbian/Debian Buster: After logging-in to the gui, run sudo apt-get update sudo apt-get install sshfs mkdir ~/tmp ss...
by TimG
Thu Aug 29, 2019 6:41 pm
Forum: General discussion
Topic: raspberrypi-ui-mods
Replies: 3
Views: 1604

Re: raspberrypi-ui-mods

Ah-ha! Yes. In /var/log/lightdm/x-0.log Fatal server error: (EE) no screens found(EE) Adding hdmi_force_hotplug=1 to /boot/config.txt seems to have solved the problem. The Pi4 is running headless, and will be accessed via VNC. I don't remember that being needed on a Pi3+ with Stretch. I assume it's ...
by TimG
Thu Aug 29, 2019 6:09 pm
Forum: General discussion
Topic: raspberrypi-ui-mods
Replies: 3
Views: 1604

raspberrypi-ui-mods

It used to be possible to add the desktop environment to raspbian-lite by installing a single package (and all its dependencies): apt-get install raspberrypi-ui-mods This does not seem to be working on a Pi4 with 2019-07-10-raspbian-buster-lite.img. After running raspi-config and choosing "B4 Deskto...
by TimG
Wed Aug 07, 2019 4:49 pm
Forum: General discussion
Topic: Why moving to 64bit?
Replies: 259
Views: 28176

Re: Why moving to 64bit?

piglet wrote:
Wed Aug 07, 2019 11:56 am
jamesh wrote:
Tue Aug 06, 2019 2:44 pm
although we are learning by osmosis.
*cough* diffusion is the closer analogy, unless you've a semi-permeable membrane in the office for the information to pass through *cough*
The skull is semi-permeable to information. At least, some are.
by TimG
Mon Jul 08, 2019 11:22 pm
Forum: General discussion
Topic: Power Supply for multiple RAPI4B+
Replies: 19
Views: 3049

Re: Power Supply for multiple RAPI4B+

The official RPi power supply is actually hard to beat on price and reliability. There are industrial power supplies which would be more compact, but good ones aren't cheap -- especially once you factor in cabling, connectors, and a ventilated case. Cheaper power supplies are the cause of endless di...
by TimG
Tue Jul 02, 2019 6:33 am
Forum: General discussion
Topic: Raspberry Pi 4 Thread - general discussion
Replies: 945
Views: 128178

Re: Raspberry Pi 4 Thread - general discussion

Just a guess, but it looks to me like the extra componentry there is related to the USB hub. On closer examination it looks like the power circuitry is for the VIA chip and SOC. I guess the main power chip does not generate all the necessary voltage levels. That still leaves the two 8-pin chips nea...
by TimG
Mon Jul 01, 2019 11:45 pm
Forum: General discussion
Topic: Raspberry Pi 4 Thread - general discussion
Replies: 945
Views: 128178

Re: Raspberry Pi 4 Thread - general discussion

Purely out of curiosity, what are the Pi4's extra components around the audio jack? PWM drivers and a stabilised power supply? How is the Pi4's audio quality compared to previous models?

LHS: Pi3B+
RHS: Pi4
pijacksmall.jpg
pijacksmall.jpg (155.48 KiB) Viewed 1895 times
by TimG
Sun Jun 30, 2019 4:58 pm
Forum: General discussion
Topic: Bluetooth audio glitches (with Pi-3 only)
Replies: 1
Views: 404

Re: Bluetooth audio glitches (with Pi-3 only)

I noticed (systemctl status hciuart) that the bluetooth communication is 3Mbps (with flow-control) on the 3B+, but only 0.92Mbps (without flow-control) on the 3B. Both should be sufficient for an A2DP audio stream, but it's the only difference I could spot. Anyway, now that Buster is out (*before* D...
by TimG
Mon Jun 24, 2019 4:42 pm
Forum: General discussion
Topic: Raspberry Pi 4 Thread - general discussion
Replies: 945
Views: 128178

Re: Raspberry Pi 4 Thread - general discussion

As the WiFi is just a module, I assume it is still fine for RS/Farnell to have orders for customised Pi4 without the WiFi/BT module there. Cutting the antenna trace would be sufficient, shirley? And/or a solder blob shorting it to ground. No, I'm not going to try it on my soon-to-arrive Pi4. Bravo ...
by TimG
Mon Jun 24, 2019 4:20 pm
Forum: General discussion
Topic: Simple circuit to step down 120VAC
Replies: 3
Views: 261

Re: Simple circuit to step down 120VAC

Here's a couple of useful links: https://designercircuits.com/DesignNote1c.pdf https://hackaday.com/2017/04/04/the-shocking-truth-about-transformerless-power-supplies/ Even though you need very little power, you do need mains-rated fail-safe components. It's usually cheaper and easier to find a disu...
by TimG
Sat Jun 22, 2019 12:52 am
Forum: General discussion
Topic: Bluetooth audio glitches (with Pi-3 only)
Replies: 1
Views: 404

Bluetooth audio glitches (with Pi-3 only)

Hi Everybody, I have set up a Pi as a bluetooth speaker, and I'm getting prominent audio glitches every few seconds. The odd thing is it *only* happens with a Pi-3B using the built-in bluetooth. Other Pi models are not affected. Does anybody know if this can be cured? A Pi-3B+ and the *same* uSD car...
by TimG
Wed Jun 12, 2019 10:59 am
Forum: General discussion
Topic: Running an RPI outside?
Replies: 12
Views: 845

Re: Running an RPI outside?

Re. power: To avoid putting mains power in a box exposed to the weather, I've used an old 18V laptop power supply in combination with a small regulator like these: https://www.tracopower.com/products/browse-by-category/detail/dc-dc-converters/non-isolated-step-down-regulators/ The 18V supply (the ex...
by TimG
Tue Jun 04, 2019 11:39 am
Forum: Camera board
Topic: Soldering camera cable
Replies: 1
Views: 269

Soldering camera cable

Does anybody know if the camera ribbon cable can withstand soldering? I'd like to join a PiZero-to-camera adapter cable to a normal cable without using extra intermediate connectors. https://cdn.shopify.com/s/files/1/0174/1800/products/Camera_cable_1_of_3_19028afc-2f5f-40ba-863d-293ee88ef649_256x256...
by TimG
Tue Jun 04, 2019 11:16 am
Forum: General discussion
Topic: light detector with photo transistor
Replies: 34
Views: 2362

Re: light detector with photo transistor

A digital light detector would save you a lot of work. For example, https://www.adafruit.com/product/4162 https://cdn-learn.adafruit.com/assets/assets/000/073/757/small240/adafruit_products_VEML7700TopHeader.jpg On the other hand if you want to learn about phototransistors, here are a couple of usef...
by TimG
Thu May 23, 2019 3:29 am
Forum: Advanced users
Topic: Fast boot on Pi-Zero with C library and GPIO access
Replies: 2
Views: 354

Re: Fast boot on Pi-Zero with C library and GPIO access

It's been a while since I worked on fast-booting, but on a Pi Zero it's possible to start running code within 2 - 2.5 seconds. I used a systemd service file to launch my script as early as possible, like this: # example.service # run as early as possible [Unit] Description=Example Service DefaultDep...
by TimG
Sat Apr 27, 2019 12:55 pm
Forum: Advanced users
Topic: LM386 Audio Amp Module Producing buzzing/cracking noise
Replies: 6
Views: 974

Re: LM386 Audio Amp Module Producing buzzing/cracking noise

- The LM386 has two audio inputs: inverting and non-inverting. Are they both connected to something? - The speaker output needs a DC-blocking capacitor. - Likely the USB headphone output needs a load. Connect a set of headphones in parallel. If you still get distortion, you may need DC-blocking capa...

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