[Diy_efi] GCC/ARM LPC21xx assist needed for Donegan ECM/EFI :-)

[Steven P. Donegan]

I need a fragment of code (or a completely usable piece of code) for the
following scenario:

Using the Capture/Compare and Timer functions, setup (CCP_Setup()) a CCP
register/pin with a timer such that future interrupts on that CCP will
support capturing the frequency in Hz on that CCP pin. The waveform is
expected to be 50% duty cycle.

My poor beginning on the interrupt handler follows:

/*
The short fragment of code below can be used to measure frequency on a 
capture pin. Initialize FIQ_R8 to the timer address and FIQ_R9 to -1
and 
enable the fast interrupt.

The frequency can be calculated with: (float)(PCLK * FIQ_R9) / 
(float)(FIQ_R11 - FIQ_R10)
*/

void FastInterrupt(void) __attribute__((interrupt("FIQ"), naked));

void FastInterrupt(void)
{
  asm volatile("ldr             r12, [r8,0]\r\n"
               "ldr             r13, [r8,40]\r\n"
               "str             r12, [r8,0]\r\n"
               "adds            r9, r9, #1\r\n"
               "moveq           r10, r13\r\n"
               "mov             r11, r13\r\n"
               "subs            pc, lr, #4\r\n");
}

I know there are some ARM and C people out there - this is the first
fragment I need for the ECU - it is for reading a GM MAF.

TIA!