Solar Data Logger User Guide
Cornell University
ECE 476
Microcontroller Design: Spring 2006
Final Project
Self-Powered Solar Data Logger
By Abigail Krich
Wednesday 1:30 lab

Button Functions
Button Function
Button 0 Set Time
Button 1 Set Logging Interval
Button 2 Up , Yes, Start
Button 3 Down, No, Stop
Button 4 Next
Button 5 Logging Info Display
Button 6 LCD Wake
Button 7 Upload

Setup

      When the data logger is first turned on, a series of instructions will appear on the LCD screen to step the user through the set-up process. The system will greet the user with a quick greeting and then display the message Press Upload or Y to Setup.
      Pressing the Upload button will immediately commence a data upload of any data previously stored in the logger before it was turned off. Please see the section on uploading data. Please note, if the logger lost power before it was stopped, up to 33 of the most recent logs may have been lost. Always stop the logger before turning the power off.
      Pressing the Yes button will enter the system setup to begin logging data.
      Once setup is entered, the system will ask the user to set the clock with the message “Please Set Time.” The system will then wait until the user presses the Set Time button. No other buttons are active at this time.
      Upon pressing the Set Time button, the screen will display the date and time on the bottom of the screen in the format hr:min mo/day/yr. At the top of the screen, the system will ask you to set the year. The year is stored as a two digit number. At this point, the user may increase or decrease the year by pressing the Up or Down buttons. Pressing the Up or Down buttons once will increase or decrease the year by one. Holding either of these buttons down will continue increasing or decreasing the year until the button is released.
      When the correct year has been selected, the user may press the Next button to continue by setting the month in the same way, the months being represented by the numbers 1 through 12. When the correct month has been selected, the user may again press the Next button to continue by setting the day. If a leap year is selected, the logger will allow for selection between 29 days in the month of February, otherwise it will only allow for 28. Following selection of the day, the user may set the hour and minute in the same manner.
      The user may continue to cycle between setting the year, month, day, hour and minute until satisfied by pressing the Next button. When finished, the user may press the Set Time button again to exit the time setting mode. To ensure that the full time is set, the system will not allow the user to exit the time setting mode, the first time through, until the minutes have been set. The clock will now automatically update the time.
      Upon exiting the time setting mode, the LCD screen will prompt the user with the message “And Set Interval.” At this point, if the user presses the Set Logging Interval Button, the user will be able to set the interval in the same manner as the time. The system continuously samples the insolation level and stores an average value over the logging interval to the on-board flash memory. The logging interval can range between 1 minute and 1 hour in single minute increments. The value displayed on the LCD is the logging interval in minutes. The on-board flash memory can store up to 33,792 data points. If the logging interval is set at 1 minute, the logger can operate continuously for 23.4 days before using up the memory. If the logging interval is set at 60 minutes, the logger can operate continuously for 3.8 years before running out of memory. When satisfied with the logging interval, the user may again press the Set Logging Interval button to continue with setup.
      Note: the user may re-enter either the time setting mode or the interval setting mode at any point from now on. When exiting either of these modes, the system will return to the point from which it left off prior to entering the mode.
      The LCD will next display the message “Clear Memory Y/N.” To clear any previously logged data and begin afresh, the user should press the Yes button once. The system will then ask for a confirmation and display the message “Confirm Y/N.” The user should again press the Yes button to confirm that the memory should be erased. If it is desired instead to append future data to the previously logged data already in memory, the user may instead press the No button at either of these prompts.
      The LCD will then display the message “Y Starts Logging.” When the system is positioned correctly and ready to begin logging data, the user may press the Yes button. Setup is now complete and the system will commence normal logging operation.

Normal Operation

      Under normal operation, the LCD will display the instantaneous insolation value in Watts per square meter on the first line of the LCD followed by a reading of the battery voltage. On the second line the system will display the clock time and date in the same format as in the time set mode.
      The user may reset the clock or the logging interval at any point during operation by pressing the time set or interval set buttons. There should be no need to do this during normal operation unless power is lost or the user decides to change the logging interval.
      If the flash memory becomes full during normal operation, the LCD screen will display the message “Memory Full” on the second line of the display. Until the memory is cleared, the system will not be able to log any more data, though it will continue displaying the instantaneous insolation and voltage values on the first line.
      To save power, the LCD screen will turn off after 2 minutes with no user activity. To wake up the LCD, the user may press the LCD Wake button. No other buttons are active and the system continues logging while the LCD is off.
      If the user presses the Stop button during normal operation, the LCD screen will display the message “Confirm Stop.” If the user presses the Stop button again, the logger will stop storing data to the flash memory. The LCD will then display the message “System Stopped” on the first line and “Restart | Upload” on the second. If the user did not intend to stop the system, the start button should be pressed. Until the second time the stop button is pressed, the system continues logging.
      If the user confirms the stop command, the system will then give the option of retrieving the data to a PC by pressing the Upload button. Please see the section on uploading data.

Uploading Data

      To retrieve data in the logger’s memory to a PC, connect the logger to a computer using an RS232 cable with straight-through connection. The user should start a simple terminal program, such as Hyperterminal, on the PC. The terminal program should be set to 9600 baud, no parity, one stop bit, and no flow control. Once the logger is connected and the terminal program has made a connection the user may press the Upload button. The system must be stopped to retrieve the data. This is done by either stopping the logger as described in the normal operation section or when the logger is first turned on or reset.
      Once the retrieve data button is pressed, the system will print identifying header rows followed by a row for each data point logged with the time and date at which it was stored. The LCD will display the message “Uploading Data” followed by the time and insolation value presently being uploaded. Upon reaching the end of the data, a footer row will be printed to the terminal program and the LCD will display the message “Done Uploading Please Restart.” The data in the terminal program on the PC may then be copied into another program for storage or analysis.
      If an incomplete transmission was made due to the terminal program not being ready or the connection not being made, the user may reset the logger and choose to upload the data at the first prompt. The data may be uploaded as many times as the user desires until the memory is cleared.