RE: gEDA-user: Announcement : gTAG schematics released

["Luis Miguel Brugarolas" <lmbruga@sire.es>]

> 1) I would consider opto isolating the jtag from the USB side to keep
> ground loops from doing strange things - you could conceivably have a
> loop between the gTAG board, target PCB, wall socket, wiring, PC and
> back to gTAG spanning many meters that can cause a lot of problems.
> This might be especially important in a production line environment.
At the time of Anchor Chips the USB bridge was not 5V tolerant (if my memory does not lies me). The problem of optoupling is speed. I suggest using 5 V tolerant 3.3V supplied devices.

> 6) maybe add some leds for the programmers on PA4/PA5
A LED worths a debugging day (variable on US$ quotation :-)

Just a NOTE: USB devices power has tight limits (100mA for low power devices, and 500mA for high power devices). High power devices has to be able to work with 100 mA during enumeration.

Best regards

Luis Miguel Brugarolas