About twam

My name is Tobias Müller. I'm interested in com­puters, physics, elec­tronics and photo­graphy. more …

Maker Faire Hannover 2015

Dieses Wochenende fand die dritte Maker Faire in Hannover statt und nachdem ich 2013 und 2014 nur als Besucher vor Ort war, habe ich mich dieses Jahr auf dem Stand des Chaos Computer Club Hannover als Maker versucht. Bei uns am Stand gab es neben einem Lötworkshop viele Bastelprojekte zu sehen: Unter anderem hatten wir verschiedene selbst-gebaute Tastaturen, Snake auf Flipdot Displays, Multiplayer Tetris auf einem LED Laufschriftmodul, einen LED-Effekt-Koffer, meine Time Circuits und mein LED Display dabei. Das am Stand viel blinkte und es viel auszuprobieren gab, waren wir die ganze Zeit von vielen Kids und Junggebliebenen belagert, welche entweder für sie neue Spiele (Die 'Jugend' kennt kein Tetris mehr) oder Altbekanntes ausprobieren wollten.
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Upgrading HP 6060B DC Electronic Load with front binding posts

HP 6063B Front Binding Posts

HP 6063B Front Binding Posts

A few weeks ago I scored an HP/Agilent/Keysight 6060B DC Electronic Load on eBay. Unfortunately most of these come without front binding posts as they are optional (Option 020) and have to be paid extra for. As I'm using this as a bench DC load and not in a rack-mounted test setup I wanted to have these. Luckily I had access to a HP/Agilent/Keysight 6063B DC Electronic Load with front binding posts, which is basically the same DC load with just less current and more voltage specs. Continue reading

7-segment Charlieplexing

A few weeks ago I bought the ATLYS FPGA development board from Digilent. Unlike my other two FPGA development boards (NEXYS3, BASYS2) the ATLYS does not have a 7-segment display onboard. As I often use this during debugging I wanted to add some external 7-segment display to the ATLYS board. The ATLYS boards provides two connections for add-on boards: A high-density Vmod port and a 8-pin Pmod™ port. As I'm planning to use the Vmod port for other stuff I wanted to use the Pmod™ port for the 7-segment display.

On my other two FPGA bords the 7-segment display is directly connected to the FPGA. The 4-digit 7-segment display has four anodes (one per digit) and eight cathodes (one per segment plus the decimal point) totalling in twelve pins. The display control has to be multiplexed within the FPGA. As the Pmod™ connector has only eight pins this kind of control mechanism would not work. So the most obvious alternative to send the data for pins serially and to use serial to parallel converters on the extension board. However I wanted to avoid using a lot of ICs on the boards so I went for an alternative approach: Charlieplexing. Continue reading

Screenshots over USB from Agilent DSO-X 3014A

The Agilent (now known as Keysight) oscilloscopes of the 2000X and 3000X series have a built-in USB device interface which allows them to be controlled from a USB host capable PC. It is implemented as a USB Test & Measurement Class Device (USBTMC) and is usually used by National Instruments implementation of the Virtual Instrument Software Architecture (VISA).

However there exists free alternatives such as pyvisa/pyvisa-py for Python. These allow Python to communicate with SCPI (Standard Commands for Programmable Instruments) compatible devices over RS232/TCP-IP/USB. The Agilent 2000X/3000X series oscilloscopes provide the :DISPlay:DATA? to retrieve the currently view display data as a screenshot. So I wrote a small Python script to get the data and write it to a PNG file. You can download it here: screendump.py. Continue reading