Implement CPPM reception. Keep it as an option for now.

Recalibrate the radio, as the timings have changed.
And, it seems a couple of channels are now swapped with the new radio. Or
rather, unswapped. So fix the channel map to match.

timer.h

@@ -17,10 +17,12 @@
 #define PWM_PERIOD ((4*PWM_MAX)+1)
 
 #define TIMER_INPUT_TIMEOUT (TIMER_PCLK/10)
+#define TIMER_CPPM_SYNC 40000
 
 #define TIMER_CH(x) (timer_map[x])
 
 extern volatile unsigned int timer1_width[];
+extern volatile unsigned int timer1_cppm[];
 extern unsigned int timer_map[];
 
 void init_timer(void);
@@ -35,5 +37,9 @@ bool timer_allvalid(void);
 #define timer_delay_us(x) timer_delay_clocks((x)*TIMER_US)
 #define timer_delay_ms(x) timer_delay_clocks((x)*TIMER_MS)
 
+#ifdef TIMER_CPPM
+#define timer_input(ch) (timer1_cppm[TIMER_CH(ch)])
+#else
 #define timer_input(ch) (timer1_width[TIMER_CH(ch)])
+#endif
 #endif /* __TIMER_H */