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by jokkebk
Thu Dec 27, 2012 1:58 pm
Forum: Other projects
Topic: Pi as Arduino Shield (HDMI)
Replies: 0
Views: 793

Pi as Arduino Shield (HDMI)

I've seen a couple hacks using the Pi as a cheap(ish) ethernet shield for Arduino, and I decided to continue along similar lines, and made a tutorial on how to transform the Pi to a "HDMI shield" for Arduino: http://codeandlife.com/2012/12/27/raspberry-pi-as-arduino-hdmi-shield/ The basic principle ...
by jokkebk
Wed Aug 15, 2012 7:29 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Simple GPIO performance benchmark
Replies: 33
Views: 24109

Re: Simple GPIO performance benchmark

Thanks for jbeale for his excellent tips on improving the ground lead. I replaced the alligator clip -> male-to-female jumper wire -setup with a short piece of wire, and used the probe head directly on the GPIO pin generating the signal (the Pi resetted twice during those attempts...). The resulting...
by jokkebk
Tue Aug 14, 2012 7:49 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Simple GPIO performance benchmark
Replies: 33
Views: 24109

Re: Simple GPIO performance benchmark

I've now updated the benchmark with wiringPi results. I also re-ran the C benchmarks with a better 200 MHz scope and probes to ensure the reported frequencies and waveforms were accurate (they were, except for the detailed shape of 22 MHz signal which is now updated to the article as well). Also, th...
by jokkebk
Tue Jul 10, 2012 7:46 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Help with RS232 GPIO connection
Replies: 35
Views: 14615

Re: Help with RS232 GPIO connection

If you're looking for a DIY solution instead of a ready-made 3.3V TTL cable, I wrote a RaspPi serial tutorial for MAX3232CPE just a week ago, with Clear Pictures of Everything(tm) :) http://codeandlife.com/2012/07/01/raspberry-pi-serial-console-with-max3232cpe/ In the example I'm connecting from PC ...
by jokkebk
Wed Jul 04, 2012 5:46 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Simple GPIO performance benchmark
Replies: 33
Views: 24109

Re: Simple GPIO performance benchmark

All the versions I tested had quite a small variance in the minimum, maximum and average frequency which seems to indicate the latency is most of the time very small (the frequency is basically a function of the latency, if the logic level takes 1ms to change, freq would be ~500 Hz). Unfortunately I...
by jokkebk
Tue Jul 03, 2012 7:31 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Simple GPIO performance benchmark
Replies: 33
Views: 24109

Simple GPIO performance benchmark

Today I finally had time to investigate GPIO programming further, and decided to see how fast the GPIO pins can be driven using different programming languages / libraries. The test setup was to generate a simple square wave as fast as possible and measure the frequency with an oscilloscope. Detaile...
by jokkebk
Sun Jul 01, 2012 5:36 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: GPIO UART tutorial with MAX3232CPE
Replies: 1
Views: 10646

GPIO UART tutorial with MAX3232CPE

I noticed that there are already a few blog posts around that pinpoint the RX/TX pins on the GPIO header, but most only mentioned that "because Pi is 3.3V, you'll need some type of converter such as MAX3232CPE to communicate with RS-232 voltage levels". I happened to have the MAX3232CPE at hand, so ...

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