PCB with eight sensors
Building a custom CO₂ sensor has become a popular hobby project in the last weeks due to the COVID-19 pandemic. For that reason I ordered multiple Sensirion SCD30 CO₂ sensors. Sensirion claims an accuracy of ± (30 ppm + 3% MV) at 25 °C and the sensor supports an Automatic Self-Calibration (ASC) (see section 1.4.6 of datasheet).
As I noticed quite some difference between measurements of different sensors, I was curious about the accuracy and self-calibration. Therefore I build a custom PCB, which hosts eight sensors in vicinity, a Bosch BMP280 pressure sensor for pressure calibration, a I2C multiplexer and an ESP32 for low-level communication with the sensors. Continue reading
When I used FPGAs in the past, e.g. for my LED Display, I was using Xilinx FPGAs with their proprietary software which unfortunately runs only under Windows or Linux. This was very inconvenient and in addition the software was slow as hell.
Fortunately a new era has begun: Open-Source FPGA toolchains! It was started some time back by Clifford Wolf, who first wrote a synthesis tool called Yosys and later reverse-engineered the bitstream format for Lattice iCE-40 FPGAs. Recently a new place-and-route tool called nextpnr was developed as well. Continue reading
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
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.