TeleMetrum Low-level Access
	CC1111 4-wire debug interface:
		debug data, debug clock, reset, ground
	CP2103 -- 4 GPIOs controlled from USB
		One USB packet per half clock
	Beagle USB hardware monitor
	CC1111-based debug link
		emulates serial on USB
		provides high-level commands

TeleMetrum Software Development Environment
	Small Device C Compiler, targeting 8051 CPU
	Source Debugger for SDCC
	Hex debugger using either CP2103 or CC1111 link
		Emulates mcs51 emulator
		Except talks to real hardware
		Hooks up to sdcdb

AltOS architecture
	Multi-threaded
		Avoids the 'one big loop'
	Non pre-emptive
		Limits where pre-emption can occur
	sleep/wakeup rendezvous
		Good enough for Linux
	Timers, mutexes
		Basic OS services

Flight software architecture
	Flight progress tracked through discrete states
		Pad - Sitting vertically
		Boost
			Acceleration > 2g and Speed > 5m/s
			or
			Height > +20m
		Fast
			Acceleration < -1/4g
			or
			Boost period > 15s
		Coast
			Speed < 200m/s
			or
			Height < Max_height - 500m
		Apogee
			Height < Max Height - 10m
		Main
			Height < Main Height
		Land
			Acceleration stable for 5 seconds
			Height stable for 5 seconds
			Height < Launch height + 1000m
	
Calibration
	Radio calibrated by adjusting PLL against freq counter
		48MHz crystal good to 20ppm
		20ppm at 434MHz is 9Khz
	Accelerometer calibrated by rotating board on bench
		Accelerometer output runs through 5V->3.3V divider
		Uses 1% resistors
		Also automatically adjusts for 100G/50G/40G devices

GPS adventures
	Problem: GPS looses satellites during boost phase
	GPS receivers track sats by synthesizing expected signal
		frequency based on relative velociy
		phase based on distance
	Change in actual signal means changing synthetic signal
		High acceleration means allowing faster changes
	Change rate limited by 'loop filter' bandwidth.

Drag race plots

Standard flight plot set