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by MarkTF
Thu Jan 03, 2019 3:20 pm
Forum: General discussion
Topic: 2 x pi sending signal.
Replies: 5
Views: 216

Re: 2 x pi sending signal.

You won't damage GPIO pins connected together if they are inputs (duh?) or if any that are outputs are set to the same logic level. Thus you can emulate "open collector" (open drain) outputs on a RPi by setting the GPIO Pin to be an input when it is inactive and setting the GPIO Pin to be an output ...
by MarkTF
Wed Dec 19, 2018 3:42 pm
Forum: General discussion
Topic: pi one still supported?
Replies: 17
Views: 1271

Re: pi one still supported?

The original Pi was more sensitive to power supply irregularities than later versions so it would be worth trying different USB power brick and cable combinations.
by MarkTF
Thu Nov 29, 2018 6:44 pm
Forum: General discussion
Topic: Using hot glue to mount 3B ?
Replies: 7
Views: 1016

Re: Using hot glue to mount 3B ?

Would Velcro Tape work? That would make it far easier to remove the Pi if necessary.
by MarkTF
Thu Nov 29, 2018 6:31 pm
Forum: General discussion
Topic: Arduino how TTL Converter
Replies: 11
Views: 701

Re: Arduino how TTL Converter

I'm not entirely clear on the question you're asking, but this might be the answer: The Arduino Uno has a USB to Serial converter on the board that is normally used to communicate between a PC and the Atmel microcontroller. If one removes the Atmel microcontroller (on socketed boards) or disables th...
by MarkTF
Mon Nov 12, 2018 7:12 pm
Forum: General discussion
Topic: Programming Software for Raspberry PI
Replies: 11
Views: 1770

Re: Programming Software for Raspberry PI

I expect code development, compilation, and execution on the Pi under Raspbian is the most common approach, but it is possible to develop on Windows and cross compile for the Pi. It's not at all like Arduino where the target processor simply isn't capable of hosting it's own development system. The ...
by MarkTF
Mon Nov 12, 2018 6:26 pm
Forum: General discussion
Topic: Powering RPi inside of PC case
Replies: 17
Views: 2303

Re: Powering RPi inside of PC case

Thanks to both of you. I don't care much about keeping it on while the pc is off, because I'll be measuring operating temps with the sensors. I guess beating up the SD card with improper shutdowns is a concern, but this PC is always on. If all you want to do with the sensor data is to display some ...
by MarkTF
Thu Nov 01, 2018 5:00 pm
Forum: General discussion
Topic: iPhone 5S Camera
Replies: 8
Views: 892

Re: iPhone 5S Camera

My stack of old phones is mostly Android, not iPhone, but for Android there are apps available that enable wifi streaming from the phone to a connected computer's browser. If such an app is available for iPhone, and I'd be surprised if there weren't, that would seem to be the way to go. Once you've ...
by MarkTF
Mon Oct 08, 2018 3:32 am
Forum: General discussion
Topic: "Unfortunately, I do not have a scope, nor does anybody I know."
Replies: 12
Views: 1315

Re: "Unfortunately, I do not have a scope, nor does anybody I know."

drgeoff wrote:
Fri Oct 05, 2018 11:12 am
For logic capture the £5 Salae and USBee clones on ebay are a useful addition to your toolbox.
And they can be run with SigRok software on a RaspberryPi.

https://sigrok.org/
by MarkTF
Sat Sep 15, 2018 1:41 pm
Forum: General discussion
Topic: Voltage divider and raspberry
Replies: 5
Views: 749

Re: Voltage divider and raspberry

Probably the best information one can find is for the RPi Compute Modules. For these the maximum input leakage current is 5 microAmps suggesting a worst case input resistance over 0.6 megaOhms and a typical input capacitance of 5 picoFarads. The net of this is that using a voltage divider to do leve...
by MarkTF
Wed Sep 12, 2018 1:01 pm
Forum: General discussion
Topic: Struggling to get an ADC working
Replies: 6
Views: 430

Re: Struggling to get an ADC working

The reason no PI has an ADC is that the SoC in the PI was not designed for such a use case. . . . Its actually quite rare for a "computer chip" to support analog circuitry, its really the microcontrollers like those used in an Arduino that are an exception, but these use a far less dense silicon pr...
by MarkTF
Mon Sep 03, 2018 4:09 pm
Forum: General discussion
Topic: Raspberry Pi is a waste of time (and money).
Replies: 115
Views: 12086

Re: Raspberry Pi is a waste of time (and money).

Premise 1: The stated mission of Raspberry Pi is education.

Premise 2: No one ever learned anything meaningful by blindly following a recipe and having it 100% work.

Mission accomplished.
by MarkTF
Thu Aug 23, 2018 12:31 pm
Forum: General discussion
Topic: Wirelessly charged Rpi Zero?
Replies: 14
Views: 1352

Re: Wirelessly charged Rpi Zero?

It's certainly electronically possible to wirelessly charge a battery and provide "pass through", that is provide power to the ultimate load simultaneously. Here is one such device, that, as I read its specifications, will do this: https://www.amazon.com/MobilePal-Next-Generation-10000mAh-Wireless-C...
by MarkTF
Thu Jul 26, 2018 12:57 pm
Forum: Python
Topic: Drawing live graphs using python and matplotlib [solved]
Replies: 2
Views: 431

Re: Drawing live graphs

I don't have an example at hand, but inserting a short Matplotlib pause after showing the plot seems to be a key part of the magical incantation if you're not already doing so.

e.g.

Code: Select all

import matplotlib as plt
...
...
plt.show()
plt.pause(0.001)
...
by MarkTF
Mon Jul 23, 2018 12:17 pm
Forum: General discussion
Topic: Is it suitable? For a Computer Science course?
Replies: 44
Views: 3726

Re: Is it suitable? For a Computer Science course?

When I was in college (circa 1980) a friend of mine had a (surplussed and ancient even then) PDP-4 in his dorm room with nothing for I/O but the toggle switches and blinky lights on the front panel. According to Wikipedia only about 54 PDP-4 computers were ever made. I wonder if your friend still h...
by MarkTF
Mon Jul 23, 2018 4:32 am
Forum: General discussion
Topic: Is it suitable? For a Computer Science course?
Replies: 44
Views: 3726

Re: Is it suitable? For a Computer Science course?

. . . The mid/late 90s and I was one of the few people to have a computer. . (I wasn't computer sci) When I was in college (circa 1980) a friend of mine had a (surplussed and ancient even then) PDP-4 in his dorm room with nothing for I/O but the toggle switches and blinky lights on the front panel....
by MarkTF
Wed Jul 18, 2018 3:48 pm
Forum: Advanced users
Topic: Power Rpi 3 B+ from led strip PSU
Replies: 6
Views: 547

Re: Power Rpi 3 B+ from led strip PSU

Looking at the Pi3 and Pi3+ schematics, the specified input voltage upper limit for the regulator is about 5.5 V, so putting 12 V in would almost certainly fry the board.

You can get efficient 12 to 5 volt regulators from a number of sources. e.g. https://www.pololu.com/product/2850.
by MarkTF
Wed Jul 18, 2018 11:46 am
Forum: General discussion
Topic: VNC Viewer Size
Replies: 2
Views: 318

Re: VNC Viewer Size

I'm not familiar with Macs, but in Linux one can start multiple VNC servers each with their own resolution. e.g. vncserver -geometry 720x480 which, if successfully started, will return the port number for the VNC service. Each VNC service started will open on a different port. Thus <MacBookIPaddress...
by MarkTF
Tue Jul 17, 2018 1:42 pm
Forum: General discussion
Topic: Image processing in Matlab with Raspberry pi
Replies: 2
Views: 314

Re: Image processing in Matlab with Raspberry pi

For a timelapse photography application with a USB webcam, I used the "pygame" module to do frame capture. There is a tutorial on the pygame website: https://www.pygame.org/docs/tut/CameraIntro.html It sounds like you are doing the actual image processing on a different platform, but it is worth not...
by MarkTF
Thu Jul 05, 2018 12:48 pm
Forum: General discussion
Topic: Powering Up the ESP8266
Replies: 3
Views: 384

Re: Powering Up the ESP8266

You don't specify which ESP8266 board you're using, so I'm going to strongly suggest that you start with one of the ESP8266 boards with a USB port, such as NodeMCU, the Sparkfun ESP Thing, or similar. The rational is that the design of ESP8266 power is fairly critical and a board that has on board r...
by MarkTF
Thu Jul 05, 2018 12:26 pm
Forum: General discussion
Topic: Proposal: Raspberry Pi Zero W with 2GB / 4GB embedded
Replies: 28
Views: 2475

Re: Proposal: Raspberry Pi Zero W with 2GB / 4GB embedded

You could save money by removing the SD card connector (and, for me and probably for all people that makes small things with small memory, you could remove also the HDMA connector and the camera connector; by the way a "super-lite" distribution that would take <1GB or <512MB could be another idea Y...
by MarkTF
Thu Jul 05, 2018 12:16 pm
Forum: General discussion
Topic: Raspberry Pi 3 communication with arduino
Replies: 2
Views: 264

Re: Raspberry Pi 3 communication with arduino

I've played around a bit with Firmata, but most everything I've done in this realm has been to write application specific Arduino code directly (C++ with Arduino library infrastructure) and export the data over USB serial to the host (PC or RPi) for post-processing, visualization, etc in Python. I'm...
by MarkTF
Sun Jun 10, 2018 9:52 pm
Forum: Advanced users
Topic: Looking for a Guru's Help Setting Up Lubuntu on RPi3+
Replies: 4
Views: 729

Re: Looking for a Guru's Help Setting Up Lubuntu on RPi3+

Step by step instructions 1. Wait for release of 18.04 LTS for RPi3 to appear here: https://ubuntu-pi-flavour-maker.org/download/ 2. Follow instructions listed at link. I'm a long time user of lubuntu on Intel PCs and have used it on ARM in the context of Linux on Android. I've not used it on RPi as...
by MarkTF
Wed May 30, 2018 6:46 pm
Forum: Advanced users
Topic: Brief voltage drop on UPS like system. would a capacitor fix it?
Replies: 53
Views: 5827

Re: Brief voltage drop on UPS like system. would a capacitor fix it?

Yeah, I considered that, but if I put it on the other side of the switch, won't it allow leakage and help drain the battery faster than it already does (the regulator is permanently running the boost converter) Electrolytic capacitors do have some leakage current, but it typically is on the order o...
by MarkTF
Sun May 13, 2018 2:04 pm
Forum: General discussion
Topic: Radio Modules Getting Random Noise?
Replies: 3
Views: 400

Re: Radio Modules Getting Random Noise?

The library you are using looks to have different protocol options, selected via the '-t' argument. You might try using one of the different protocol options. From my experience with the receiver, 2, 4, or 5 might be more promising but the PWM over the air protocol doesn't seem very robust for this ...
by MarkTF
Fri May 11, 2018 9:14 pm
Forum: Graphics, sound and multimedia
Topic: AM/FM tuner suitable for Pi?
Replies: 17
Views: 12040

Re: AM/FM tuner suitable for Pi?

Not to butt in, I'm actually looking to add an AM radio receiver so I can monitor static electricity discharge, which would upset the sound on AM radios . . . There exist purpose built lightning detectors. This one claims to have some logic to differentiate between lightning and man-made static dis...

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