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Topic: First schematic / board, please validate? (Read 3439 times) previous topic - next topic


Nov 05, 2010, 04:18 am Last Edit: Nov 05, 2010, 04:18 am by graynomad Reason: 1
Oh, and don't be afraid to rip up and start again.

Well said. I just binned a PCB design I'd spent a week on, often that's the best way to get a good job.

Same with software, a few years ago due to some slackness on the backup front I lost a project I'd been working on-an-off with for a month.

After tearing my hair out for a while I realised it was a golden opportunity to do it better as there were many things I wasn't real happy with but not to the point I could face doing it again voluntarily.  After a few days I was back to the level of functionality I had before the disk crash and had a better product.

The second time around you've already done most of the thinking, in both the above cases the redo took just a fraction of the time the original took, and the end result was much better.


Rob Gray aka the GRAYnomad www.robgray.com


The shield of the USB connector is connected to anything. I wouldn't mind seeing that connected to chassis.

I can't find a better reference than this at the moment but my understanding is that the shield should not be connected on devices:

USB cable shielding:

Shield should only be connected to Ground at the host. No device should connect Shield to Ground



I think that's true (although I've heard arguments both ways), only connect the shield(s) in one place.


Rob Gray aka the GRAYnomad www.robgray.com

Tim Williams

Grounding is more religion that science. I've seen it at least three ways--connected to ground at one end, both ends, or neither. You ask ten engineers how it should be done and you will get a dozen different answers.

From the USB specification 2.0:
6.8 USB Grounding
The shield must be terminated to the connector plug for completed assemblies. The shield and chassis are bonded together. The user selected grounding scheme for USB devices, and cables must be consistent with accepted industry practices and regulatory agency standards for safety and EMI/ESD/RFI.

Alastair DSilva

You might also want to consider an SMD mini-B connector - I find getting the legs aligned on the through-hole varieties a bit fiddly.


Can anyone recommend a good PCB and assembly house? Ideally send them a circuit design and parts list and receive complete board in return.

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