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by PiGraham
Tue May 22, 2018 8:51 am
Forum: C/C++
Topic: Increase GPIO toggle frequency
Replies: 24
Views: 552

Re: Increase GPIO toggle frequency

Hrater,
Thanks for those posts. They are very useful.
by PiGraham
Sun May 20, 2018 7:18 am
Forum: C/C++
Topic: Increase GPIO toggle frequency
Replies: 24
Views: 552

Re: Increase GPIO toggle frequency

If I were to look at using hardware SPI instead, how would that work given that these devices don't have a CS pin? Would I manually pull down one of the RPi CS pins, write the data (using the existing MOSI and CLK channels), and then pull the 'fake' CS pin HIGH? I'd really like to avoid hardware SP...
by PiGraham
Sun May 20, 2018 6:31 am
Forum: C/C++
Topic: Increase GPIO toggle frequency
Replies: 24
Views: 552

Re: Increase GPIO toggle frequency

That's a very fair point. I will have numerous other SPI devices in use in the very near future, and would prefer to keep these drivers separate if at all possible. Another consideration is the fact that I'll be moving to a non-RPi Linux device in the near future as well, the SPI details of which I...
by PiGraham
Wed May 16, 2018 8:14 am
Forum: Automation, sensing and robotics
Topic: monitoring rotary encoder on fast motor with pigpio - improving performance?
Replies: 13
Views: 349

Re: monitoring rotary encoder on fast motor with pigpio - improving performance?

My take is finding ways of doing things on the Pi without having to resort to additional hardware is a win win situation. The person doing the development learns a lot and it lowers the entry cost for everyone else wanting to experiment in the area - they may not need to spend money and time buying...
by PiGraham
Tue May 15, 2018 8:15 pm
Forum: Beginners
Topic: LED Strip colouring in reverse with PiGPIO
Replies: 18
Views: 390

Re: LED Strip colouring in reverse with PiGPIO

Yeah, you're right - it's not a MOSFET! It's a regulator, and the bottom line says -3.3, so it's a 3v3 version That makes for a novel power switch! I suppose that raising the ref pin to 3.3V turns the regulator off and dropping the voltage to zero puts it into normal regulator mode with shorted out...
by PiGraham
Tue May 15, 2018 6:43 pm
Forum: Automation, sensing and robotics
Topic: monitoring rotary encoder on fast motor with pigpio - improving performance?
Replies: 13
Views: 349

Re: monitoring rotary encoder on fast motor with pigpio - improving performance?

Yu are pushing the limits of what's practical under Linux. You could offload the counting to hardware. There ate quadrature counter ics that can cope with high rate encoder counting. Your coide could then just query the position when it needs it using i2c. Pushing? Yes, reached? No. So why add more...
by PiGraham
Tue May 15, 2018 6:37 pm
Forum: Gaming
Topic: Exagear and Games
Replies: 9
Views: 352

Re: Exagear and Games

I have a Raspberry Pi 3 B+ which I am using as my desktop computer. I am planning on purchasing Exagear. However, I wish to legally purchase games for Exagear. Does anyone have any suggestions? I find it difficult to find information. Isn't the point of exagear to run PC x86 software on other platf...
by PiGraham
Tue May 15, 2018 6:33 pm
Forum: Advanced users
Topic: Mean of 60 temperature sensors
Replies: 17
Views: 673

Re: Mean of 60 temperature sensors

As scruss points out it's the cabling that is the catch to this situation. The OP says it's a large area commercial building with three stories and 50 to 60 sensors per story for a total of 150 to 180 sensors. This could be many miles of wires through a potentially very noisy environment and having...
by PiGraham
Tue May 15, 2018 9:43 am
Forum: Automation, sensing and robotics
Topic: monitoring rotary encoder on fast motor with pigpio - improving performance?
Replies: 13
Views: 349

Re: monitoring rotary encoder on fast motor with pigpio - improving performance?

You can use pigpio from c which should hep a bit. Yu are pushing the limits of what's practical under Linux. You could offload the counting to hardware. There ate quadrature counter ics that can cope with high rate encoder counting. Your coide could then just query the position when it needs it usin...
by PiGraham
Fri May 11, 2018 10:45 am
Forum: General discussion
Topic: E ink as Monitor for raspbian Lite
Replies: 4
Views: 212

Re: E ink as Monitor for raspbian Lite

i was hoping to just use the bash terminal. But does the refresh rate suggest you can't see what you typing for a second? I was looking at this display here http://www.ebay.co.uk/itm/like/123098315023?clk_rvr_id=1526739387782&vectorid=229508&lgeo=1&item=123098315023&rmvSB=true. But i can much docum...
by PiGraham
Fri May 11, 2018 10:29 am
Forum: General discussion
Topic: Model train project help
Replies: 9
Views: 413

Re: Model train project help

Options that I would consider are; PyGame https://www.pygame.org/news A python library for creating multimedia applications. It has functions to draw lines, or more complex widgets on screen. Tkinter - Pre-installed with most python distributions. A slightly old fashioned but powerful GUI framework...
by PiGraham
Thu May 10, 2018 7:45 am
Forum: Troubleshooting
Topic: Pi still has some power after removing power cable
Replies: 8
Views: 261

Re: Pi still has some power after removing power cable

There is a 5V feed on HDMI isn't there? On later Pi (except Zeroes) a self-powered high-side FET (AP2331W,RT9741CGV) is used to steer the Pi 5V to HDMI H5V. My underestanding is that should prevent back-feeding from the TV to the Pi. Curious. The HDMI seems to be the only possible source of power i...
by PiGraham
Thu May 10, 2018 7:36 am
Forum: General discussion
Topic: Flame Sensor
Replies: 11
Views: 337

Re: Flame Sensor

Since the DO os open collector it make no difference to that signal what voltage is connected to Vcc on the module. I suggest using the specified 5V. Use a pullup to 3.3V either using the built-in pullup or an external resistor. According to the sensor schematic "D0" has an internal pullup (R2 - 10...
by PiGraham
Thu May 10, 2018 7:22 am
Forum: Raspbian
Topic: Display file "real time" like in a console?
Replies: 9
Views: 294

Re: Display file "real time" like in a console?

Code: Select all

tail -f mylogfile 
For details on following a file that is changing see:

Code: Select all

man tail
by PiGraham
Wed May 09, 2018 5:19 pm
Forum: Troubleshooting
Topic: Pi still has some power after removing power cable
Replies: 8
Views: 261

Re: Pi still has some power after removing power cable

There is a 5V feed on HDMI isn't there? This looks relevant if not a simple answer: https://www.raspberrypi.org/forums/viewtopic.php?t=2518#p32811 There is the MHL standard which is intended to supply charging power whilst being a HDMI sink, so a TV would supply power to a device plugged into it. Al...
by PiGraham
Wed May 09, 2018 4:50 pm
Forum: General discussion
Topic: Flame Sensor
Replies: 11
Views: 337

Re: Flame Sensor

Thus the flame sensor "Vcc" must be connected to 3.3 V on the RPi rather than 5 V as in the Arduino example. This keeps the output "D0" in the proper voltage range for RPi, that is 0 V and 3.3 V. Since the DO os open collector it make no difference to that signal what voltage is connected to Vcc on...
by PiGraham
Wed May 09, 2018 4:09 pm
Forum: General discussion
Topic: Flame Sensor
Replies: 11
Views: 337

Re: Flame Sensor

It should be OK to use with RPi According to the circuit posted by MArkTF the output DO is drivern by an LM393 comparator and the TI datasheet for that says this about the output: The output of the LM193 series is the uncommitted collector of a grounded-emitter NPN output transistor. Many collectors...
by PiGraham
Wed May 09, 2018 1:55 pm
Forum: General discussion
Topic: Flame Sensor
Replies: 11
Views: 337

Re: Flame Sensor

If you want help using a sensor or other device you need to tell people what it is that you have (or intend to get). A link to a product page or data sheet is usually most useful.
by PiGraham
Wed May 09, 2018 11:32 am
Forum: Python
Topic: Help a fool aka building a selfie box for a wedding
Replies: 3
Views: 119

Re: Help a fool aka building a selfie box for a wedding

The search term "photobooth" may help you. I suggest that taking the photos is much more important than printing them on the spot so get the photo taking working first and embellish later if you have time. You could get by without a GUI. Some lights and a button and a preview display would do as a m...
by PiGraham
Sat May 05, 2018 8:26 am
Forum: Automation, sensing and robotics
Topic: Sensor to detect presence within 100ft?
Replies: 6
Views: 274

Re: Sensor to detect presence within 100ft?

Wi-Fi should work over 100ft. You could probably get Bluetooth to work at 100ft with a directional antenna. You could use GPS on your phone to detect when you're within 100ft and do something. Phones don't have so many other options. If it doesn't have to be your phone doing the sensing you use IR ...
by PiGraham
Fri May 04, 2018 7:17 pm
Forum: Automation, sensing and robotics
Topic: Sensor to detect presence within 100ft?
Replies: 6
Views: 274

Re: Sensor to detect presence within 100ft?

Wi-Fi should work over 100ft. You could probably get Bluetooth to work at 100ft with a directional antenna. You could use GPS on your phone to detect when you're within 100ft and do something. Phones don't have so many other options. If it doesn't have to be your phone doing the sensing you use IR b...
by PiGraham
Fri May 04, 2018 1:53 pm
Forum: Beginners
Topic: Pi for a gym?
Replies: 4
Views: 124

Re: Pi for a gym?

Another option could be to make the button bashing do frame advance of a video so that the speed of playback relates to the speed of running and the quicker the video finishes the faster your time. That way you could have real world scenes, cartoon animation etc. I think OMXplayer used to have a fra...
by PiGraham
Fri May 04, 2018 1:45 pm
Forum: Beginners
Topic: Pi for a gym?
Replies: 4
Views: 124

Re: Pi for a gym?

You could also look at consoles. The Wii balance board detects steps (among other things) so you could use a standard game that uses a stepping game mechanic. Not Pi based, but it would be an easy as Pie option.
by PiGraham
Fri May 04, 2018 1:43 pm
Forum: Beginners
Topic: Pi for a gym?
Replies: 4
Views: 124

Re: Pi for a gym?

The simplest option that occurs to me is to go for a "button bashing" game like Track & Field / Hyper Olympics.You should eb able to run that on a Pi using an emulator like Emulation Station in distribution RetroPie. You should be able to configure the emulator to use GPIO pins as controller inputs....
by PiGraham
Fri May 04, 2018 9:37 am
Forum: Python
Topic: Problems with shaking servo motors
Replies: 4
Views: 187

Re: Problems with shaking servo motors

There may be better options for servo PWM than RPi.GPIO. I think the trick is to use DMA. PIGPIO does that. I think you can use that through GPIOZERO or it has a Python interface. You could also look at Servoblaster. You can't get 100% perfectly stable PWM on general gpio under Linux because it's no...

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