# Owl firmware version 0.5.2

The primary purpose of this firmware is to allow Orbit NTNU to transmit APRS data at fixed intervals while primarily using the radio for telemetry and command (using NGHam) for their balloon mission.

General note on firmware 0.5.x: This version uses a complex routing scheme (using callsigns as address) to route packets between the different serial ports and the radio.

## New commands

### "port-rf-mute"

Set to 1 to prevent data from ports being transmitted. Useful to e.g. transmit generated APRS data without accidentally sending incoming data from port on same frequency.

### "mice-symbol"

Set APRS symbol table and symbol. E.g. jogger is "/[" and balloon is "/O"

### "autoexec-cmd"

Type one or more commands to be automatically executed.
Use escape sequence for newline ("\n") to separate commands.
 
Example transmitting APRS and then going back to ngham mode:
autoexec-cmd port-rf-mute 1\nmode ax25-1k2\nfreq 144800000\nmice-tx\nfreq 144950000\nmode ngham\nport-rf-mute 0
 
### "autoexec-int"

Set autoexecution interval in seconds, e.g. "autoexec-int 60" for once per minute.

## Config example: Balloon radio

// General config
access always
power mid
// SSID 11 is common for balloons
mycall LA3JPA-11

// Mic-E/APRS config
// Notice the use of two spaces after "path", to set an empty path
path  
mice-cmt Owl VHF test, \vV \tC HDOP\h
// Send comment with every third transmitted packet
mice-cmtint 3
// Mic-E msg. 7 means "Off duty"
mice-msg 7
// Will show a balloon symbol on the map
mice-symbol /O

// Every 60 second, switch to APRS frequency and AX.25 mode to transmit APRS,
// then switch back
autoexec-cmd port-rf-mute 1\nmode ax25-1k2\nfreq 144800000\nmice-tx\nfreq 144950000\nmode ngham\nport-rf-mute 0
autoexec-int 60

// Configure port 1 for use with GNSS/GPS
baud1 9600
port1 nmea
// Don't route packets from this port to RF or other port
p1-out none
// Don't route any RF packets to this port
p1-rfilter none
// Don't route any port packets to this port
p1-pfilter none

// Configure port 0 for use with NGHam serial port protocol
port0 ngham-spp

// Save then apply port config, alternatively save before "port0 ngham-spp" 
// to get back into command parser after reboot
cfg-save
set

Note: Radio will not transmit APRS without GNSS fix!

## Config example: Ground station radio

// Rudimentary example to generate a lot of traffic 
// (to verify that autoexec in balloon radio doesn't change mode while receiving)
access always
power mid
freq 144950000
mycall la3jpa-3
// Send source every single frame
tx-src 1
// Send statistics every single frame
tx-stat 1
// Frame duration 500 ms
tdma-frame 500

## To verify GNSS configuration works

// Make sure radio is in command mode so you can send commands to it
baud1 9600
port1 nmea
// Will print debug trace
verbose 3
// Applies NMEA parser for port1, which should configure the GNSS
set
// You should see "MSG: GPS in airborne mode" if it successfully configured the GNSS

## Lessions learned from balloon mission in 2015

Notes from previous balloon mission with NUTS in 2015, using Owl VHF to transmit APRS.

### Note on altitude

The GPS (u-blox MAX-6), was operating with default settings (Platform = Portable) which had an upper altitude limit of 12000 meters. Up to this altitude, the altitude was reported correctly. 
Fix: GNSS is configured to use airborne mode.

### Note on speed

Due to unit confusion, the speed was reported as 1.94 times the actual speed (ratio between knots and m/s). 
Fix: Units are now properly converted.

### Note on transmission interval

A timer initiated a transmit attempt approx. every second minute, but if a current transaction was in progress, such as CW or packet traffic, the APRS transmission attempt would be discarded (not postponed). The practical transmission interval was therefore much lower because there was a lot of traffic. 
Fix: Postpone transmission if radio is busy, don't discard whole packet.