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by drgeoff
Thu Apr 23, 2020 4:18 pm
Forum: Troubleshooting
Topic: P4 won't boot up
Replies: 9
Views: 330

Re: P4 won't boot up

The files does not disappear :| I use a MacBook Pro power adapter. Any advice? Where can I find logs? it has not booted. Possibly no logs. Read the "not booting" sticky, including but not limited to the specifics for RPi4B. Until a recent hardware revision, RPi4Bs do not work with USB-C PSUs that h...
by drgeoff
Thu Apr 23, 2020 2:17 pm
Forum: Wanted
Topic: Can I buy pi4 board only with one hdmi connector?
Replies: 4
Views: 1002

Re: Can I buy pi4 board only with one hdmi connector?

We have to put pi4 board to a small case, so we don't need other I/O, like usb, ethernet, pin header, and etc. Can I buy pi4 board only with one hdmi connector? Possibly Yes. (But you will probably need to order lots of them... ) https://www.element14.com/community/docs/DOC-76955/l/raspberry-pi-cus...
by drgeoff
Thu Apr 23, 2020 2:05 pm
Forum: Advanced users
Topic: radio over ethernt
Replies: 4
Views: 342

Re: radio over ethernt

Is it possible to use radio communicatio over raspberry pi built in wifi adapters? What are the minimum requirments for the wifi moudle to be used as rasio moudle also for radio over ethernt purpose? I think it would be impossible to use the RPi built in wireless network interface without using rad...
by drgeoff
Thu Apr 23, 2020 1:40 pm
Forum: Troubleshooting
Topic: P4 won't boot up
Replies: 9
Views: 330

Re: P4 won't boot up

If the ssh file disappears then the RPi has booted.

Also, wpa_supplicant.conf, not what you have typed.
by drgeoff
Thu Apr 23, 2020 12:11 pm
Forum: Troubleshooting
Topic: External 3.3v regulator?
Replies: 1
Views: 102

Re: External 3.3v regulator?

Unlikely to work for a couple of reasons. One is that the various voltage rails need to come up in a certain sequence.
by drgeoff
Thu Apr 23, 2020 8:47 am
Forum: Advanced users
Topic: Thermal differences between mutiple Pi 4B units
Replies: 37
Views: 2203

Re: Thermal differences between mutiple Pi 4B units

RPis bought at the same time from the same supplier does not mean that their CPU/GPU chips came from the same silicon wafer. There are variations. Also the temperature sensors are not individually calibrated.

IMHO a difference of 2 degrees is nothing to get excited about.
by drgeoff
Thu Apr 23, 2020 8:36 am
Forum: Beginners
Topic: Reversing Audio Jack
Replies: 5
Views: 275

Re: Reversing Audio Jack

There is no analogue input capability anywhere on any model of RPi released to date.
by drgeoff
Wed Apr 22, 2020 11:46 pm
Forum: Off topic discussion
Topic: Python 2 EoL...at least in theory
Replies: 51
Views: 4722

Re: Python 2 EoL...at least in theory

Theory and practice are not always the same.
by drgeoff
Wed Apr 22, 2020 11:19 pm
Forum: General discussion
Topic: RPI 3B not booting
Replies: 5
Views: 217

Re: RPI 3B not booting

studentRPI wrote: ↑
Wed Apr 22, 2020 6:14 pm
 I managed to format the SD and copy the OS into it.
Explain in full detail what you did and how. And state the capacity of the card.
by drgeoff
Wed Apr 22, 2020 10:52 pm
Forum: Beginners
Topic: No audio on external speakers
Replies: 8
Views: 418

Re: No audio on external speakers

https://www.raspberrypi.org/documentati ... -config.md
by drgeoff
Wed Apr 22, 2020 6:44 pm
Forum: Troubleshooting
Topic: 128GB SD card and Buster not booting
Replies: 14
Views: 500

Re: 128GB SD card and Buster not booting

I have tried the Raspberry Pi imager program to erase my 128GB which it did, but when I tried to image NOOBS and Raspbian with Desktop after 30+ minutes of the program looking as if it were writing there pops up a message that the zip/image was unable to unzip or unpack, thus a failure. What I woul...
by drgeoff
Wed Apr 22, 2020 4:01 pm
Forum: General discussion
Topic: Raspberry Pi in rental for an education program
Replies: 8
Views: 586

Re: Raspberry Pi in rental for an education program

Taking into account the costs (transport, admin and testing) required at the end of rental period, a realistic rental price is not going to be appreciably lower, if at all, than the purchase price.
by drgeoff
Wed Apr 22, 2020 11:17 am
Forum: General discussion
Topic: Pin Layout
Replies: 3
Views: 152

Re: Pin Layout

6by9 wrote: ↑
Wed Apr 22, 2020 10:47 am
 They also tried to make it so that there was a ground in a sensible place for small batches of GPIOs, so things like these simple LED traffic lights only need 4 GPIOs.
"''..... only need 4 GPIOs." should be "... only need a 4 pin connector".
by drgeoff
Wed Apr 22, 2020 10:51 am
Forum: Raspberry Pi OS
Topic: Slow booting dev-mmcblk0p2.device
Replies: 3
Views: 422

Re: Slow booting dev-mmcblk0p2.device

Hi everyone, I'm trying to optimize the boot times on my Pi4B with Rasbian Buster Lite, and I'm seeing a very slow booting dev-mmcblk0p2.device: systemd-analyze blame 4.876s dev-mmcblk0p2.device 1.743s udisks2.service 1.075s networking.service 853ms loadcpufreq.service 797ms systemd-udev-trigger.se...
by drgeoff
Tue Apr 21, 2020 12:17 pm
Forum: Beginners
Topic: Looking for schematic diagram for RPi 2011.12 rev2 + 16x2 LCD
Replies: 10
Views: 253

Re: Looking for schematic diagram for RPi 2011.12 rev2 + 16x2 LCD

pcmanbob wrote: ↑
Tue Apr 21, 2020 6:41 am
 Well as most LCD's come without header pins , I assume you soldered them on yourself so just de-solder it and solder a new pin in ,

or just clean off the corrosion with some fine wet and dry paper.
Perhaps the corrosion was on a RPi GPIO header pin.
by drgeoff
Sat Apr 18, 2020 12:17 pm
Forum: Troubleshooting
Topic: Wrong supply voltage (12Vdc) and now what can i do?
Replies: 31
Views: 1023

Re: Wrond supply voltage (12Vdc) and now what can i do?

emma1997 wrote: ↑
Sat Apr 18, 2020 1:50 am
 If you don't see 4 green blinks w/o any SD:

The regular gang are probably asleep ATM so I will fill in with the usual Time to Say Bye Bye and buy another. A bigger, faster, BETTER one!
The 4 green blinks without micro-SD card applies to the 4B model, not 3B+ which the OP has.
by drgeoff
Fri Apr 17, 2020 10:58 pm
Forum: Troubleshooting
Topic: Wrong supply voltage (12Vdc) and now what can i do?
Replies: 31
Views: 1023

Re: Wrond supply voltage (12Vdc) and now what can i do?

That polyfuse is getting hot because something else on the board (possibly the protection diode) is drawing excessive current. The polyfuse should be low resistance normally. Substituting (or bypassing it) with a piece of wire is not going to repair that RPi. Remove the protection diode and try 5 vo...
by drgeoff
Fri Apr 17, 2020 8:56 am
Forum: Automation, sensing and robotics
Topic: Best Batteries for Robot Car Motor?
Replies: 9
Views: 407

Re: Best Batteries for Robot Car Motor?

Best in what sense?

Run time
Weight
Size
Safety
Cost
Lifetime
Ease of charging
etc
by drgeoff
Thu Apr 16, 2020 11:39 pm
Forum: Troubleshooting
Topic: [SOLVED] Pi4: No video whatsoever on first-ever boot
Replies: 6
Views: 364

Re: Pi4: No video whatsoever on first-ever boot

A problem I had with my new Pi4 was the mHDMI connector. It was too short and the case made the mHDMI port hard to connect to. Try running it without the case. Another Dougie wannabe! (Can't/won't read.) The OP wrote: "Another thing I read about was that the cable connector might be too short on th...
by drgeoff
Thu Apr 16, 2020 10:41 pm
Forum: Troubleshooting
Topic: [SOLVED] Pi4: No video whatsoever on first-ever boot
Replies: 6
Views: 364

Re: Pi4: No video whatsoever on first-ever boot

Try putting the latest Raspbian on a card. Any of the 3 versions. If still no video, the usual advice is to enable ssh and run headless, logging in via ssh from another computer. That can confirm if the RPI4B is really booting and you can run the tvservice command etc for further diagnostics. ISTR t...
by drgeoff
Thu Apr 16, 2020 3:54 pm
Forum: General discussion
Topic: PWM (gpio 18 ) not outputing 3.3V
Replies: 16
Views: 742

Re: PWM (gpio 18 ) not outputing 3.3V

Have you really got a 7.2K resistor in the circuit? That is not in any of the E series preferred values.
by drgeoff
Thu Apr 16, 2020 3:34 pm
Forum: General discussion
Topic: Raspberry Pi 4 B won't boot from SD card
Replies: 18
Views: 1046

Re: Raspberry Pi 4 B won't boot from SD card

Re-install Raspbian Buster on the micro-SD card. If still failing install on another micro-SD card.
by drgeoff
Thu Apr 16, 2020 11:18 am
Forum: Advanced users
Topic: how to change between AP and normal wifi
Replies: 2
Views: 187

Re: how to change between AP and normal wifi

I have several commercial equipments which can operate in AP or station mode. All of them require a reboot when changing from one to the other.
by drgeoff
Thu Apr 16, 2020 11:09 am
Forum: Beginners
Topic: Power Consumption in Raspberry PI
Replies: 6
Views: 314

Re: Power Consumption in Raspberry PI

rpdom wrote: ↑
Thu Apr 16, 2020 8:53 am
The Pi has vastly more computing power, built in full USB, Video and network support and is multi-user and multi-tasking.
[pedant mode]
The multi-user and multi-tasking are properties of software. It is quite possible to have a RPi system with neither of those properties.
[/pedant mode]
by drgeoff
Thu Apr 16, 2020 11:04 am
Forum: Beginners
Topic: Does PWM power supply divide the current drawn of a non-inductive Load along with the divided apply voltage?
Replies: 11
Views: 528

Re: Does PWM power supply divide the current drawn of a non-inductive Load along with the divided apply voltage?

A motor must have a resistive component as well. it couldn't do any work without consuming power and pure inductances and capacitances don't consume power. That resistive part will depend on how much power , ie it varies with the load on the motor.

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