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Thursday 16 January 2020

Testing the in-car APRS map display with USB hub on tablet

Today I had to do a run out to a local branch of discount supermarket Lidl, and thought it was a good opportunity to test out the map setup using a USB hub on the tablet, however some issues came to light during this before and after leaving the house.

The first issue was APRSISCE/32 causing the WiFi adaptor in the tablet to lock up under load, meaning my phone is tethered using a USB cable (Bluetooth was tested and found to be unacceptably slow, and RF from the radio, with the cables in a certain place, would cause the USB to drop and reconnect, which would cause the tethering to switch off in the phone, the USB cable feeding the hub itself was too long anyway and I've found a shorter one in which I have fitted a clip on ferrite to to see if that helps.

The other issue was the COM port allocation for the FTM-400XDE's supplied data cable, this conflicted with a Bluetooth serial port so the number was changed over to one that was not in use, this did involve disconnecting and reconnecting the plug, and to identify the USB port in which the data cable is to always be plugged in it was outlined with blue permanent marker, the phone used one of the other ports, this allows fitting of a wireless keyboard later on

The USB hub is powered from an in-car power lead with variable voltage set at 5 volts, though the computer and hub will only dictate a maximum of 500mA current per port (the data cable won't get close to that but the phone will).

The Bluetooth GPS box, though currently not fitted to the windscreen as it was previously, worked fine stuck to the top of the dash with the blu-tack already on it and unusually got sufficient satellites from cold start which certainly impressed me.

There is still a little bit of testing to do, using the cable that I put a ferrite bead onto, and then there will be the fitting of the mount in the car which has yet to be done though if the weather is not bad I can look into it on Sunday, but to be honest I'm not holding my breath, it is the UK and winter after all.

I hope to have this working ahead of the Blackpool rally in April.

73 de M0WNU

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