USB lead causes reset ??

[davidwf]

I've mentioned it in passing in another thread without resolve so here goes on its' own ....
I am running a cct that uses a PICAXE 18X to monitor light levels and every so often need to see what's going on so I leave the data cable plugged into the circuit continuously and plug the USB lead into my (battry powered) laptop as & when I need to......this usually but not always causes a re-start of the PIC.

Have attached the relevant part of the cct showing correct (?) reset and serial input connections

Any ideas why ?

Purely by chance I did it the other way around and plugged into the cct. board last and it didn't reset but that may have been a one off...or two off ..... in fact it usually seems to be OK doing it this way but I am not convinced.

I am not using the enhanced download circuit as I understand it is not required when using the USB lead - I don't have a serial port....so much for progress !

 

[BeanieBots]

Just tried it. Yep, quite often resets the PICAXE.
Probably due to the USB chip putting a spurious 'blip' on the serin pin and making the PICAXE think a download is on the way.

The solution is to use a molex type connector (NOT the 3.5mm phono which shorts during insertion/removal) and connect the USB BEFORE connecting the PICAXE.

 

[davidwf]

The solution is to use a molex type connector (NOT the 3.5mm phono which shorts during insertion/removal) and connect the USB BEFORE connecting the PICAXE.

I'm actually using a "simple" jack socket from rapid electronics (part No 20-0144)
that won't short out the plug and doesn't have any switching functions on it .......but it seems to be the USB end that causes the problems - perhaps I will have to change my ways

Thanks for the tip