USB charging adapter
Many gadgets and tools nowadays run from 5 V and incorporate an USB port for that purpose. When developing those devices powering them from a bench power supply is usual very handy as current can be easy monitored and limited. For that purpose I wanted to create a small adapter which plugs into my bench power supplies and offers an USB type A plug.
The power and current a device may draw from an USB port is limited and follows complex rules depending on the state of USB enumeration. Many devices ignore those rules and just draw 100 mA or 500 mA independently of USB enumerate state. This works for most power providing devices and almost all USB chargers/power supplies. If more current is needed the power supply needs to signal extra capability to the device. As most USB chargers are rather dump a simple solution, or to be exact many simple solutions were invented. The device that wants to draw current checks the status of the D+ and D- signal lines immediately after attach. Continue reading
LED display @ Maker Faire
I mentioned a long term project I'm working on: A huge LED display built out of 32x32 LED RGB matrix modules driven by a BeagleBone Black
, which could drive the display like a usual monitor using a framebuffer driver. After many months and just right before Maker Faire 2015
in Hanover I managed to bring the project in a presentable state. This article shall give an overview over the project. Continue reading
As a huge fan of the EEVblog I came around EEVblog #513 - Mailbag several months ago. In this episode Dave get's an awesome time circuits clock out of the movie Back to the Future from the guys at Shackspace, Stuttgart, near my hometown Tübingen. They documented everything on GitHub, so check out their awesome project.
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
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