Strange results when writing to EEPROM

[Gelio]

Hi all,
Trying to write to internal EEPROM of PIC18F4550.
Pickit2 correctly verifies and programs the chip.
After normal run I'm trying to save some bytes into 256-byte internal eeprom. And as a result i see garbage or incomplete data.
For example, I am writing
11 22 33 44 55 66 77 88
and as a result have:
11 22 33 44 3F FF 77 88
or
00 00 00 00 55 66 FF 88
or similar.
code looks like

[Ttelmah]

First thing is your clock will not be running at 20MHz.

Assuming you have a 20MHz crystal, then your fuses need to be:

[temtronic]

I'm surprised it compiles with this...

delay(100);

unless I'm wrong it should be
delay_us(xx);
delay_ms(xx);
or
delay_cycles(xx);

another possible problem is that the WDT fuse isn't specifically set/reset. I'm unsure what the CCS 'default' is for that PIC, should be off....but.....

as well the 'debug' fuse is enabled , and 'debug' does change the setup so the PIC won't run as 'normal'....

Jay

[gjs_rsdi]

I had same EEPROM problem until made:

[Gelio]

Thank you friends,
i tried the Ttelmah code fixed.
Compiled and burned.
it works first time.
Then extended array to 256 bytes and had zeros instead of normal data.
Now trying to reduce size to find max block.
Tried 16 byte array again:

[temtronic]

2 comments....

1) using delay_cycles(xx) is ,well, kinda bad...I believe that it's solely based on the cpu clock you've chosen so that a program at 4MHz has a cycle of 1us, clock at 20 Mhz and it'll be 5 x faster. Now using delay_ms(1); will ALWAYS be a 1 ms delay regardless of the CPU speed.

2) writing to data eeprom can take 'up to 4ms' according to the datasheet electrical specs. I don't know how the CCS 'write_eeprom(x,y) is coded but if it doesn't wait 4ms or check a 'done flag', then the data may not be properly stored.

others who use the 4550 and KNOW how it all works may be able to explain if I'm write or wrong.

Jay

[Ttelmah]

The write does wait.

Problem is that as you and I both spotted, the original code won't work, so what he is posting is not what he is using.
I used delay_cycles, just to give a 'point in time' where he could stop and look at the values with a watch, since assumed (as there is no output or testing shown), that he was testing in the debugger.

He then says that my code as posted worked, but then stopped when he changed it, and kept not working when he went back. Tells us I think that 1) he did not go exactly back, and 2) that something else is actually being done/happening.

There is also the question of compiler version.

He needs to post a small compilable program that actually shows what he is doing.

[PCM programmer]

Since he has a problem related to a delay at the start of the program,
the first thing I would do is change the #fuses from NOPUT to PUT.
This will give a 65.6 ms initial delay before the PIC starts running code.

He also needs to post his current test program, and show the #fuses, etc.

[Gelio]

I tried to change the PIC unit to PIC18F2455 and set 4Mhz crystal.
Then implement similar code. All working ok.
So maybe my 4550 is somehow broken or has been burned a little.
Original crystal is 20Mhz. PICKIT2 writes code and eeprom ok, erases ok and verifies ok. Only when running execution in normal mode there is problem.
Will clear project and make again and post test here.

[Ttelmah]

[Gelio]

At 2455 seems all ok...

Please, help to choose Baud rate for UART:
CONFIG1 Fuse is 0x8E22
Crystal is 20 000 000
How to calc correct Baud rate for #use232 string?
Thank you.

[Ttelmah]

Er. You don't calculate anything. You specify the baud rate you want. The #USE does the calculations for you.
What baud rate you want to use is down to what the device you are attaching to wants to use, and what the actual data rates want/need to be?.