Problem using 5V output

Technical discussions related to any XMOS development kit or reference design. Eg XK-1A, sliceKIT, etc.
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Problem using 5V output

Postby japus » Tue Nov 23, 2010 2:28 pm


I'm trying to link an XBee device to the 5V output on the XC-1A but when I power it up, the board keeps on resetting itself untill I disconnect and reconnect the power cable to the XBee.
With a second XC-1A (I'm lucky to have 2), even reconnecting the cable won't help. It just keeps on switching off and back on again.

I've attached the 5V and GND of the XBEE to the corresponding places on the XC-1A next to the prototyping area and the data in and output are connected to these ports: XS1_PORT_1A and XS1_PORT_1B on core 1.

In short: when I attatch something to the 5V supply on an XC-1A it keeps on resetting itself.

What could be wrong?


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Postby Bianco » Tue Nov 23, 2010 3:44 pm

Do you use USB power or external adapter?
How much current is the xbee asking?
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Postby waluigi » Tue Nov 23, 2010 7:27 pm

It does sound like overcurrent (or even a short?), but I await you to tell us all you're using the external power supply, then I will have to rack my brains again.
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Postby japus » Tue Nov 23, 2010 9:55 pm

I don't use an external power supply yet but if it is overcurrent, it shouldn't work by just reconnecting the wire. I think.
Or has it got something to do when powering up the board, I can't directly use the required current for the XBee. I'll go with that one. In the meantime, I'm looking for an external power supply...

Thanks for the replies!
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Postby bsmithyman » Thu Nov 25, 2010 12:37 am

Correct me if I'm wrong, but don't the XBee units need 3.3V instead of 5V? If you're using a different adaptor board to regulate it from 5V, it might be worth looking at its documentation to see how much current it draws. Some of the XBee chips use 200-300 mA at 3.3V if I recall correctly, and especially if it's a linear regulator taking it down to 3.3V, that could be most of the USB port's capacity.

You could also try adding a capacitor across the 5V line to take some of the load if in fact it is just a spike and not a constant draw. This could cause some unpredictable effects though (including causing the same resetting problems as the radio if the draw to fill it trips the over-current detection). It seems like an external adaptor (or battery pack) is your best bet.

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