changed UART0 (wired serial) from 9600 to 4800 baud, to match GPS
basic GPS pin control functions
test GPS power on/off
talking to two UARTS separately
echo GPS NMEA out Bluetooth modem
test pulsing GPS on/off line
test of NMEA sentence filtering
Removed old comments, trying to find why PB0 (GPS_ON/OFF), as an output, needs a pull-down.
moved force-SDcard-power-off earlier in initialization
comment out some old test code
moved uart init earler, before I2C init
try testing I2C start timeout
tweaking timing; correctly detects I2C failure, but does not continue normally yet
more tweaking; still not continuing normally
now correctly continues if no I2C bus error
some uart diagnostics on I2C bus fail
improved I2C failure diagnostics
tighter code, better diagnostics; circuit error was I2C SCL & SDA tied together by 10k resistor, but neither tied to Vcc