https://nagimov.me/tags/raspberry-pi/Recent content in raspberry pi on Spaghetti Code with BeerHugo -- gohugo.ioen-USThu, 18 Aug 2016 20:56:00 -0800https://nagimov.me/post/alsa-utils-arecord-bug-lots-of-.wav-files-ignoring-duration-parameter/Thu, 18 Aug 2016 20:56:00 -0800https://nagimov.me/post/alsa-utils-arecord-bug-lots-of-.wav-files-ignoring-duration-parameter/I ran into a rather funny bug recently – when recording audio on an RPi with Raspbian Jessie via an external USB sound card, arecord doesn’t stop recording after a period of time specified by --duration flag, but keeps running and filling files *-01.wav, *-02.wav, etc. with garbage data. Googling doesn’t return a solution, except an obvious one to killall -KILL arecord. USB microphones are also affected. Since I have another RPi running Wheezy and showing no symptoms of the bug (and being free of systemd malware ;), the bug is likely in arecord itself.https://nagimov.me/post/calibrating-max31855-thermocouple-amplifier/Mon, 15 Aug 2016 17:55:00 -0800https://nagimov.me/post/calibrating-max31855-thermocouple-amplifier/Maxim 31855 chips are cheap and simple to use K-type thermocouple amplifiers. They’re equipped with a digital SPI interface with libraries available for both Raspberry Pi and Arduino boards. MAX31855 breakout boards are available from Adafruit. The datasheet specifies the accuracy of ±2°C within the temperature range from -200°C to +700°C. However, close to the lower bound of this range, the accuracy of reported temperature is affected by linearized volt-to-degree conversion.