So the first CoreOne PCB was going well initially; PSU section worked fine, reset circuit fine with a minor modification, clock generator was alive.
And then the first XEF216-512-C20 chip I fitted went out of alignment when soldering the large pad - and it took a lot of heat to get it back off. The second chip went on fine - apart from a couple of stubborn solder bridges. This is partly because the pads extend to far back under the device - which I can fix with a layout change.
However after some checks and a power up something was very wrong! I tracked it down to 1V0 being connected to 3V3 through approx 0.9Ohms resistance - this would increase if you heated the XMOS chip up. No obvious solder bridges (which would give 0 ohms in any case).
So seems chip number 2 was dead from the start; not sure why, if it was my soldering. I tried to be reasonably gentle - I can not see a soldering spec in the datasheet. Trying to remove this from the PCB resulted in damaged to the board writing it off.
The XE216-512 and XEF216-512 variants are expensive, and I can not find stock of the XE216-256 or XEF216-256 chips which are half the price. Farnell says mid June for these.
In the mean time I may respin CoreOne with the pads adjusted and the reset circuit fixed. I may also spin a CoreTwo with less I2S and only 1 clock gen just to make life easier. I don't mind wasting a little money; but I don't want to keep burning through £15 ICs without getting anything out of them.
Oh well, onwards and upwards!
An electronics engineer and a long term electronics hobbyist. I like tinkering with stuff and making things.