I had the Bitwise Arithmetic project working (with your help).

I let it set for two or three days with no power now when I power the NerdKit up the program does not run, just a blank LCD. If I switch the switch up for running a Make file I get the expected two bars across the LCD.

What happened? Are the programs loaded into a volatile memory?

I lost my windows server this morning so my web site is down, so I do not have a picture of the project.

Thanks for the help, Ralph

The program is stored in flash memory on the chip. It will not go away by sitting. Something else must have changed. Look the circuit over closely. Make sure your oscillator circuit is good and that the power is configured properly.

Rick

Hi Rick, then what happened, if it didn't leak? I have one of my chips just for the array, I took it out and was programming another chip for about an hour, I put the chip for the array back in and it was dead, dead, dead. It wouldn't even take a reflash until I moved the port. No kidding, that one got the cake prize for January. Now I'm off to look up volatile memory, should be interesting.

Programs are burned into flash memory on the chip. They will not go away from sitting. My led array has been sitting with no power for over a month, I just plugged it in and it still works like the day I programmed it. The only "volatile" memory in the micro-controller is the SRAM. That will lose anything in it when the power goes away. But your programs are not store in RAM they reside in a flash ROM.

Think of your program storage in the mcu like a thumb drive you use for your PC. Once you write the data to the thumb drive, you can unplug it from your PC and the data stays there. A year later, you could plug that thumb drive back into your PC and still read the data off it.

Your micro-controller has 3 basic types of memory in it. 2 of which are non-volatile.

1. Flash Memory - (non-volatile) - used for program storage. Flash memory is a type of eeprom that is written in large blocks.
2. EEPROM - (non-volatile) - can be used for data storage and can be written by and read from a program. EEPROM (Electronically Eraseable and Programmable Read Only Memory) is typically written a byte at a time (depends on the frame size of the EEPROM).
3. SRAM - (volatile) - used for data and cpu usage during program run. SRAM (Static Random Access Memory) will lose it's data when the power is removed.

Whatever is happening is not a result of the program evaporating into thin air. There has to be other factors at play. Farmer, you've seen enough (strange happenings) to know there are a lot of variables. :)

Rick

Got it going, everything had looked correct and I'd get the two bars for program upload but not the program.

I replaced the wires that were often coming out with 22 ga. copper they have a much better purchase in the bread board now the program works as expected.

Thanks for the help, Ralph

Glad to hear you got it going. Sometimes the troubleshooting process can be frustrating.

Rick