Vermes
Advanced Member level 4
This device may be useful when you need more ports for transmission by RS232, for example when you need three ports, while Atmel provides only two. The idea was to use a small Atmega to change information received from serial to parallel form, while changing it to easy to read form, or finding time, date and coordinates among the information sent by the receiver. Additionally, the main system was relieved from work associated with the conversion and a “small” Atmega was used to determine the segments of road as pulses occurring after driving every 100 meters. Unfortunately, Atmega64 and up has two 16-bit counters which were needed for this purpose. One counter was used for the speed and the second for road.
The signal from the vehicle hub is taken from the ABS sensor. In this case, each turn of the wheel (about 2 m circumference) is counted for 100 pulses with an amplitude of 12V. Thus, the counter counts in a wide range, and additionally you have to create a simple pulse shaping system. Why parallel form instead of what gives the GPS receiver in transmission RS232? It is about the work speed, as well as the limited number of pins in the main processor (Atmega16).
The program was written in AVRStudio.
The whole device cooperates with the receiver HOLUX M1000, one of the functions of which is quite quick transmission 38400 bods and additionally BlueTooth usually used by cell phones. The receiver does not have to be very expensive. Interface has the possibility to be programmed in serial transmission range and will adapt to most receivers with RS232 signals in CMOS-TTL voltages.
Attachments to the original thread include schematic, PCB and description of registers.
Link to original thread (useful attachment) - Interface równoległy do GPS
