Tag Archives: usb

Serial download from a digital tachograph in python

Digital tachographs are a compulsory equipment for heavy trucks in the european union. The companies owning these trucks have to download the data at least once every 3 months.

Without dedicated hardware, this was so far not easily possible in linux, but my python script should make it possible to download the data with a serial cable with the right connector.

Posted in Computers, Vehicles | Tagged , , , | 15 Comments

USB Controller for 12 RC Servos

This article describes building a small (3.3 cm times 3.3 cm) RC servo controller using an avr microprocessor and an FT232RL USB-uart chip. All RC servo signals can be set to pulsewidths from 0 to 8.1 ms using the usb-serial interface.

RC Servos are popular among modelling and robotics enthusiasts because of their simplicity. They take a pulsewidth-encoded input, and turn accordingly with relatively high torque. They have their disadvantages, for example one cannot tell if the servo was able to get where it was sent, but their low price and the fact that driver and gear box are integrated make up for that. Also, Conrad sells them for 3 € a piece, so I bought some.

Posted in Electronics | Tagged , , | 1 Comment


This device connects to a computer’s usb port and controls two small electric motors using the L293D. The atmega microcontroller uses the firmware-only USB driver from objective development.

Device description

The usbmot device controls up to two small motors, 600 mA current each, 1.2 A peak each, with an atmel atmega microcontroller connected to some host device via USB. The speed of the motors can be controlled with PWM.


Both firmware and host software are in the software package at the end of this page. In order to recompile the firmware, you will need an avr build chain (for example avr-gcc and avrdude), which you probably have if you found this page. To compile the host software, you will need a c++-compiler and the qt development package.

Posted in Electronics | Tagged , , | 13 Comments