Greetings,
I am attempting to hook up an EM-406A to a wireless router that is running OpenWRT Kamikaze 8.09, and I am running into some snags.
The EM-406A came to me as part of the Globalsat BR-355 package. This package comes with an adapter that is a USB to serial, and also appears to have a level shifter in it. If I understand correctly, the EM-406A is using logic-level (TTL) voltages.
The router is an OM1P from www.open-mesh.com. This is a Accton MR3201A device, the same as the popular La Fonera FON2100 router. According to this documentation, the router is using 3.3v on its serial port:
http://wiki.openwrt.org/oldwiki/openwrt … fon/fonera
I presumed that 3.3v means TTL voltages, thus I presumed I could hook up the EM-406A to the serial port on the router with ease.
For my testing I am powering the EM-406A unit from a 5v power supply. I then hooked up the RX, TX and ground wires to the USB-serial adapter that came from Globalsat. I then plugged the adapter into my laptop.
On my laptop I used the gpsctl tool from gpsd to configure the EM-406A to send NMEA instead of binary. On my laptop I can now cat /dev/ttyUSB0 and see NMEA strings (after setting the serial port speed to 4800, of course).
Leaving the connections to the USB-Serial adapter I then make additional connections to the router: I hook up the TX and ground from the EM-406A to the router.
On the router I set the serial port to 4800 and try cat /dev/ttyS0
But all I get is garbage, no nice NMEA strings. Meanwhile, the laptop is still receiving the NMEA strings just fine. I’m not sure if my problem is software or hardware. I made many assumptions with the hardware so I don’t feel confident that the hardware is correct.
If someone could comment on the hardware hookup that would be much appreciated.
Cheers,
robert