new to EEPROM

[Alan Anderson]

Originally Posted by Bomberofdoom

The user-programmable PIC in the Robot Controller has 1024 bytes of EEPROM in it. Reading a byte from EEPROM is easy: set the address and read the value. Writing is a bit more complex: set the address, set the value, flip some control bits, wait a specific amount of time, flip some more bits, wait, flip, wait, done. Kevin Watson wrote a library that takes care of all the details behind the scene, so all you need to do is call the functions that read and write values. It keeps a buffer of requested data writes so you don't have to wait around for it to finish each time you want to change a value.

It might help if you consider EEPROM to be the equivalent of a data file on disk. You can make changes to it which will not disappear when the RC is powered down. Kevin's camera communication and servo tracking code uses EEPROM to store configuration values. The TechnoKats this year adapted and extended the idea to hold PID calibrations for the drivebase and arm, as well as the desired pan and tilt values for driving to the target light. Instead of changing #defines in the code, recompiling, and downloading every time we want to modify a value, we just use a menu-driven system to change the numbers directly on the robot.

[Bomberofdoom]

Originally Posted by Alan Anderson

Instead of changing #defines in the code, recompiling, and downloading every time we want to modify a value, we just use a menu-driven system to change the numbers directly on the robot.

Ok, how do I do that?

[JBotAlan]

As everyone else has said, you have 1024 bytes of EEPROM. What they haven't said is how to use it...

When you have Kevin Watson's EEPROM code installed, you call EEPROM_Write() with the address you want to write to (this needs to be between 0 and 1023, inclusive) and the value you want to write. Later on, call EEPROM_Read() with the address you wrote to, and it will return the value saved in EEPROM.

If you call EEPROM_Write(0,1); (which writes 1 to the first byte, byte 0, in EEPROM) then call EEPROM_Read(0); it will return 1. This lasts even if the controller loses power--if you called EEPROM_Write(x,y), and that's the last byte you wrote to that address in EEPROM, EEPROM_Read(x) will always return y.

The controller doesn't care where you save data in the EEPROM; it is entirely up to you. I suggest making a quick spreadsheet listing which address is what.

The best part about EEPROM is that all of it is at your disposal. The default code does not touch EEPROM at all. You can use every byte, 0 to 1023, for whatever you want. You could even make it a 1KB flash drive, if you want (but I'm not sure if you could find a good enough MP3 encoder to get your music compressed that small... ).

If you need specific code, I can probably supply it, but you learn best when you figure it out yourself--try it!

Happy coding
JBot

EDIT: If you want a menu-driven system, you will need to build it yourself. Check into some more of Kevin's code--there is an example of a terminal in Kevin's "Bells and Whistles" camera code. You will need his serial driver (no point in writing that yourself...it's a lot of gross low-level garbage) at the very least.

Again, I'll help you with the specifics if you really can't figure it out, but I'd like you to take the plunge yourself.

[tseres]

thanks. ya..i figured out how the camera tracking values use the eeprom, now i'll just have to play around with it. maybe a menu driven system? or maybe autonomous stuff....

[Bomberofdoom]

Yep, thank you all and thank you tesers for asking