read_configuration_memory for User ID

[tinley]

I am trying to read the User ID on a PIC18F2685.

According to the manuals...

[Ttelmah]

The offset, is the offset _inside the configuration memory area_. Not the offset from the base of memory.

The configuration memory internally is read by a separate operation to a normal memory read, and it is the offset in this that the operation expects.

You need to be using the getenv function that reads the devID area, not the read_configuration_memory function.

It's worth understanding that the memory layout seen by the programmer is _not_ how the PIC internally sees it's memory. It's like EEPROM, which internally has to be read by separate code to access the EEPROM, but the programmer writes to it at an address in the main memory range.

[tinley]

Thank you for this further insight, but even after searching the manual for the function you suggest, I am none the wiser! Another case of very poor CCS documentation!

The documentation clearly says that:

read_configuration_memory([offset], ramPtr, n);

should read User ID if using the correct offset. But it doesn't? And no indication of what the offset should be is given?

I was looking for the string I stored in the user ID, using the huge 'for loop' in desperation!

I can't find any reference to the devID in the manual?

[Ttelmah]

getenv("ID")

Returns the device user ID

Look at #ID (which sets this).

Remember the preprocessor can only 'see' what is set in the code.

The reason the manual can't tell you the locations for anything is it is always device specific. However as I already said the locations for read_configuration_memory are 'configuration memory' relative.

If you just want to do a direct 'read' from the actual chip, in code, then use the read_program_eeprom instruction, not the read_configuration_memory instruction. The latter is built specifically to talk to the configuration memory (which needs a different bit set in the read operation). The ID locations are not actually in this part of this memory space.

[tinley]

Thank you for your continued help. Sorry if I am being a bit thick!

char array[8];
array=getenv("ID");

returns error 'lvalue is read only'?

[Ttelmah]

You can't just move strings with =. You have to use strcpy. This accepts constant values.

[tinley]

So, I have finally sorted this out. For anyone else wanting to do the same thing, this works.

I want to manually type the ID into the IPE User ID, but you can test it with the following line in code, which puts the characters 1,2,3,4,5,6,7,8 into the user ID:

[Ttelmah]

As I said:

Use 0x200000 for the User ID.

[tinley]

Thank you, yes, agreed. And I had already said that in my original question!

What I needed, as others may need, is how to read the User ID from configuration memory!!!

Hopefully I have given them that now!