Posted on May 28, 2015 at 12:43One thing to point out about the L151. You can not program the Flash memory while running from Flash memory. The code that copies the 32 long's from RAM to Flash to program the Flash must be running from RAM. If you are using IAR EWARM, you can declare a function with the qualifier ''__ramfunc'' and the compiler will copy it to RAM during initialization (just like initializing static variables) and will link it for the destination address in RAM. Nothing special is required to call it. After you have set up everything, you can just call that function to do the deed to one half-page.
The code will look something like this:
__ramfunc void __PageWrite(uint32_t *RAM, uint32_t *Flash, uint32_t *FLASH_SR)
{
register int i;
for(i=0; i<32; i++) {
*Flash++ = *RAM++;
}
while(*FLASH_SR&1);
}
This is not finished code, just some high level ideas. For reasons I do not recall, in my code I actually pass a pointer to the FLASH->SR register, rather than using the standard FLASH->SR interface. I think I was trying to minimize the amount of code in RAM.
On the EWARM compiler, the arguments automatically become register variables. This means this function does not use any space on the stack and runs completely out of registers. Using only minimal optimization enabled in the compiler, the generated assembly code is as compact as any code written natively in assembly.
Now for the potentially fatal flaw in the code. If any code called by an interrupt is running from Flash, this code must be called with interrupts disabled. This means that you either have to relocate your entire DFU application to RAM, or have interrupts disabled for an extended period of time which will make USB extremely unhappy.
I hope this helps.
