Summary

This is a complete project with following features:

• Serial Data (received by built-in RS232 port of the PIC18F) logging with receive date/time
• Compact Flash data storage
• Last record display in character LCD
• Built-in RTC (DS17885) with  battery backup
• Setting the date/time and retrieval/erasing data via PC RS232 port

History

This project was done in order to receive and log serial data from a lighting location finder. We wanted to replace the PC used as the data logger with a less battery consuming reliable data-logger. We ended up designing and constructing our very own data logger for this purpose. The same data logger was also used as data logger for an unmanned weather station.

The Hardware

• The design is based on a 40 pin PIC18F microcontroller. We have successfully tested this with PIC18F452, PIC18F458 and PIC18F4580.
• A 40 x 2 character LCD is used as the display.
• We used a 128MB CF card in the initial design and also tested with a 512MB card.
• DS17885 RTC with built-in lithium battery
• The CF card, LCD and the RTC share PORTD as the data/address bus. This minimizes required pins from microcontroller.
• MAXIM RS232 transceiver IC supporting flow control (4Tx and 4Rx pins)
• For pin connection of devices with microcontroller please refer to header files and ‘main.c’ main program file.

The Firmware/Software

• Compact Flash data routines are based on MintyMP3 project. Used with some minor modifications and also altered to be compatible with HI-TECH PIC18 compiler.
• RTC routines were written by me and are as same as what’s uploaded here
• Delay, LCD and Serial port code is based on Shane Tolmie’s routines.
• Serial port data retrieval is interrupt driven to minimize data loss. Maximum record length is  492 characters. Each record should be terminated with a CRLF. The maximum number of records is either 2^32-100 or the maximum number of LBA sectors in the CF card.
• Records are saved as null-terminated strings preceded with date-time of the reception.
• Uses hardware flow-control to signal not-ready while writing to CF card.

Download

Download the complete project: CF-DAQ

Acknowledgement

Atmospheric and Lightning Research Group, Department of Physics, University of Colombo