Electronics

Speeding up your SPI MAX7219 LED displays when using Arduino and LedControl Library In preparation for the arrival of my GPSDO[1], I’m doing a quick build of an “Atomic Clock” display to have above my lab equipment. I’m using a cheap, small eight digit red LED SPI-controlled display. It uses the MAX7219 controller that I got from eBay for next to nothing. I plan to parse the RS232 information from the GPSDO unit and display the exact time. I’ll also post error messages if the GPS signal lock gets lost. I’ve done a quick prototype using an Arduino Uno, but I plan to try to get an Attiny85 to work as the controller when I’ve finished the parser and the rest of the software. After doing some research, naturally, there was a library available to connect to my LED display called LedControl. It’s part of the standard Arduino libraries (in the download section). But when I checked the code, it uses the Arduino routines to shift out the SPI data to the display. It’s great if you want to be able to use any pins to connect to the screen, but using Arduino’s bit manipulation tools for “bit-banging” the display is slow. ...

I’ve finished the OCXO upgrade. Read about it here While browsing on eBay for my new lab at home (I’m getting into electronics again), I came across a Philips PM6665 Frequency Counter, an old but functional unit so I couldn’t resist, I had to buy it. So I downloaded the Users Manual and Service Manual for the frequency counter and started to check the schematic. As usual the unit, when new, could be bought with several options. One of them was a better crystal oscillator, an MTCXO that can be automatically calibrated using a 10 MHz external reference, giving an accuracy of 3*10-8 but my unit doesn’t have that option, unfortunately. This will be fixed though. But it does have a 70 MHz to 1.3 GHz optional input! So here’s what I plan to do… ...

Running LTspice IV on Mac OS X Before I start testing a new idea for an electronic circuit and building it on a breadboard, I usually want to check it with LTspice. It’s a fantastic piece of software for testing almost any kind of component. Nearly all manufacturers have a spice equivalent for most of their parts. But there’s a snag. The Mac version of LTspice is a piece of crap. Having to run a virtual PC or reboot using BootCamp feels unnecessarily slow and convoluted. But there’s a way of running it as a “normal” Mac application. Here’s how to do it. ...

I got myself a four channel 50MHz oscilloscope to be able to do some measurements. The Rigol DS1054Z. It’s expensive in Sweden if you buy it from a local retailer, but I ordered mine from Batronix in Germany and thanks to being part of the EU, there’s no customs and extra taxes added to the price. The oscilloscope is easily hacked to 100MHz and a lot of other functions like serial protocol decoding and also more memory depth. RS232/UART, I2C and SPI decoding, advanced trigger functions like RS232/UART, I2C, SPI, Runt, Windows, Nth edge, Delay and Timeout trigger. Search for “Rigol DS1054Z hack,” and you’re on your way to transform your scope to a much more expensive version. But don’t enable the 500µV option. The oscilloscope doesn’t support it in hardware, so you will run into bugs if enabled. I’ve been delighted with my purchase, except for the occasional bug. But today it went into a total haywire mode. When trying to start it up, it hangs on boot. Either by just showing the Rigol boot screen, or show the standard display but remain immune to any input from the controls. Panic! But thankfully I found a solution to my problem. ...

“Mapping WiFi Signals in 3 Dimensions” 3D wifi plot image Adam Fabio, Hackaday: [Charles] is on a quest to complete ever more jaw-dropping hacks with the popular low-cost ESP8266 WiFi modules. This week’s project is plotting WiFi received signal strength in 3D space. While the ESP8266 is capable of providing a Received Signal Strength Indication (RSSI), [Charles] didn’t directly use it. He wrote a simple C program on his laptop to ping the ESP8266 at around 500Hz. The laptop would then translate the RSSI from the ping replies to a color value, which it would then send to the ESP8266. Since the ESP8266 was running [Charles’] custom firmware (as seen in his WiFi cup project), it could directly display the color on a WS2812 RGB LED. A great hack. It’s amazing to actually be able to see the reception of the Wi-Fi signal mapped as a 3D object. Shows that just moving a router/receiver a small amount can have an impact on reception. ...

My Raspberry Pi Car Audio Player A lot of people are using the excellent Linux microcomputer Raspberry Pi and install it in their cars. Usually, they use a color screen that is touch sensitive, being able to play back video and music. But I’m only interested in high-quality audio playback, being able to have all my CDs in lossless FLAC format for optimal sound quality. So a 16x2 LCD with some buttons is plenty. I now have a working system (but not yet installed in my car.) here’s a description of how I’ve built it. Most of the installations I’ve seen the use of the audio out from the Raspberry Pi, but it’s only 11-bit and sounds like crap. I want to use an external DAC, and you can get that to work in XBMC, but only menu and music output, not films. There are some HDMI to audio converters, but I’ll instead use a quality USB DAC. http://youtu.be/wzmFZlpbBCQ ...

Adafruit TRINKET – Mini Microcontroller – 3.3V and 5.5V versions: It’s a tiny microcontroller board, built around the Atmel ATtiny85, a little chip with a lot of power. A cool cheap little Arduino compatible board for smaller projects. The 3.3V version runs at 8MHz and the 5V version can run at 8 or 16MHz. It has five I/O pins available and comes with 8kb of memory. It can be programmed with AVRDude or the Arduino IDE after some small modifications. Looks great!

Crystal cMoy Freeform Headphone Amp: Very cool transparent cMoy headphone amplifier, made using clear casting resin. This is something I have to try. Via 0pachira

Update: You can find my latest update on the progress of my Raspberry Pi Car Audio System here. I’m working on a Raspberry Pi as a music player in my car. I’m putting all my music on a SSD disk in lossless FLAC. I’ve already got hold of a 2x16 character LCD with six button from Adafruit that only uses two pins for communication with I2C. It’s easy to program and it has four different background colors. ...

How to use interrupts with Python on the Raspberry Pi and RPi.GPIO » RasPi.TV: We’ve finally got interrupt capability on the Raspberry Pi for GPIO programming in Python using RPi.GPIO. Interesting! Saving this link for later experimenting. Need buttons for my Carputer Raspberry Pi. Via Scoop.it!