Raspberry Pi Forums

karrika

One board that would be simple to design is a board where every GPIO pin has a diode to protect over voltage by accidentally connect 5V to the pins. It could also have the ProHAT stuff for easy tinkering.

karrika

Without knowing anything about this board. The op-amp in the photo requires 4V to 6V for operating properly. A bit dangerous to connect it directly to a GPIO pin. It also just amplifies the sound. If you connect it to 3.3V only the op-amp will not work. The problem with the mechanical switch shows t...

karrika

I am currently printing in PETG. As most plastic bottles is PET I wonder if I could recycle bottles into filament at home for my 3D printer.

That would also be a good excuse to get a few extra bottles of Coke on my way home

karrika

Before you decide to delete it you could have a look if it is a mount point. In bash: mountpoint 091c1e96-1ff1-4e62-980e-5d1193cf7ae4 If it happens to be a mountpoint you should not delete it but unmount it instead. sudo umount 091c1e96-1ff1-4e62-980e-5d1193cf7ae4 My guess is that this lives in /med...

karrika

Connecting buttons directly between a GPIO pin and ground is ok. But you may need 10 buttons instead of 8. You can omit the last button KEY_EXIT and assign a Vulcan key in the Adafruit-Retrogame driver. This means that you assign a "hot-key" like KEY_SPACE and a 2nd key like KEY_B. When these are pr...

karrika

The speed of sound is 0.34 mm / us. If you want to find out where you hit with mm accuracy you need at least to sample with 3us resolution.

karrika

I may be a bit late to get into this discussion. I am currently using Cura and I am almost happy with the result. My original models are mostly created on Blender. Blender already knows a lot about geometry primitives and it also has an open source Blender CAM extension for CNC milling. In the long ...

karrika

Available in Miscap as well.
http://discohat.com/miscap/
http://discohat.com/shop/

karrika

The zip archive contains a checksum by itself. Any errors are detected automatically even without an external checksum.
So I don't get the point here.

Unless you are scared about a forged zip file by an evil villain.

karrika

I also got a SELPHY CP910 in May for a party. For some reason it was never able to print any processed images so I just shot my images on a SD card and manually moved it to the printer for printing. Do you lose something in quality or speed when you connect it to a computer? What kind of data can it...

karrika

This topic has been discussed earlier. See viewtopic.php?p=963106#p963106

karrika

Dual UART's won't work. There is no ALT configuration to get a second UART on the GPIO pins.

What works is getting two Raspberry Pi's and let them share the data over the network. Or get an USB-serial cable from your nearest electronics shop for €15.

karrika

Yes. Opto-isolators are good. And if you want to protect the optos from blowing up you could also add a reverse diode. I actually do this on my DiscoHAT - the pro-version

karrika

My suggestion is to use Cat cables. The Ethernet cables work very well for long distances. You have 4 twisted pairs in one cable. 50 ft is no problem. To reduce noise you need a much smaller capacitor. This is the way I have connected the pins. The capacitor to ground is 10nF, the series resistor to...

karrika

Did you see the technique for reading the light under the peg? I actually did this for HeroQuest at Ropecon 2016. https://www.raspberrypi.org/forums/viewtopic.php?p=1017452#p1017452 Now after the event I know a lot more. It is easier to read high intensities than low intensities. So by rapidly scann...

karrika

And for all you pointer and malloc fans here is my entry ;) #include <stdio.h> #include <stdlib.h> #include <string.h> #define TIME_STRING_LEN 40 int main(int argc, char *argv[]) { char *buf; int hours; for (hours = 0; hours < 24; hours++) { buf = calloc(1, TIME_STRING_LEN); if (buf) { int shown_hou...

karrika

Er, "Most of the time you don't need to use them"? I use them in practically everything I do! Do you never use 'malloc'? But I am almost exclusively embedded, perhaps that makes a difference. Nope. I cannot remember using dynamic memory allocation for years. Of course you have to learn to deal with...

karrika

Er, "Most of the time you don't need to use them"? I use them in practically everything I do! Do you never use 'malloc'? But I am almost exclusively embedded, perhaps that makes a difference. Nope. I cannot remember using dynamic memory allocation for years. Of course you have to learn to deal with...

karrika

I just read through the MagPi C booklet. Well written. Personally I would have left out the hairy details of pointers. You could have written the code in a way to avoid using pointers and saved that stuff for the last chapter. In my opinion pointers is the most difficult thing to understand in C. Mo...

karrika

markpedersen wrote: For now we've been researching and developing with a penchant for open-source technologies, and have thus settled on Android as OS.

Perhaps a little research about Raspberry Pi would have revealed that it is not running Android as OS.

karrika

I have been maintaining the cc65 compiler especially for Atari Lynx for many years. Part of the fun is to be able to draw something on the screen, read inputs from joysticks or keyboards and create your own masterpiece. In the old retro world we had a Tiny Graphics Interface library. tgi_setcolor(CO...

karrika

K&R notation is green, saves quite a bit of paper by not wasting empty lines on the '{' bracket... and you can see more lines in an editor. I've been programming in C for >35 years, K&R RULEZ!!!! You've been doing it wrong for 35 years? ;-) What! I had no idea you could do it in any other style tha...

karrika

Thank you for the correction. Overlays they will be. Device tree naming is not one of my strong points.

karrika

Thank you for the explanation PhilE. I did not have place for an eeprom on my DiscoCap for PiZero so it is very tempting to add a dtoverlay for at least this card. On the other hand I am not in a hurry with this. It is nice to know that the path exists to include dt blobs in the releases. Of course ...

karrika

I have noticed that many add on boards have managed to get their overlays in the stock Jessie image. In a way this has the benefit that you can update the code. As an example my DiscoHAT has an eeprom. Should I duplicate the content of pi3-disable-bt-overlay.dts in the HAT eeprom, refer to this over...

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Re: Add on boards to protect the Pi board

Re: Sensing a collision

Re: Why? (RANT)

Re: Unable to delete directory

Re: Connecting gamepad to GPIO

Re: Looking for technical people.

Re: New Old Project G-Code Slicer.

Re: Simple Pi Zero Audio Output

Re: Checksum for non zipped image.

Re: Canon SELPHY CP910

Re: Looking for technical people.

Re: How to have multiple devices on same Tx/Rx pins

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Re: Pullup vs Pulldown - Reliability With Long Wire Runs

Re: Tracking movement of game pieces on a board

Re: How would you ...... in C ?

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Re: Smart Reflection - Intelligent Mirror

Re: The MagPi does C :-)

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Re: HAT eeprom or overlay in config.txt?

Re: HAT eeprom or overlay in config.txt?

HAT eeprom or overlay in config.txt?