For just two devices
comes under the heading "famous last wordss"

I can not recall the number of times I have been told 'just' and found out that the 'just' was valid for about a day or a week.

We have, re debuuging and such, from time to time discussed "defensive programming", I would like to introduce the concept of defensive design

Defensive design, to me means that, if I am told to have two ports, I will make it (expandable to) 4 ports from the onset, if I am told that 12MHz is fast enough, I will chose a 24MHz processor.

NOW, before anyone start hollering 'cost' let me answer
a) defensive design as discussed above refer only in a limited way to 'self contained' units (no external I/O) and especially not to toys, whether 'toys' are playthings or 'cheap crap'.
b) the cost applying the above at volume will be about $0.10 per unit but will cost, at least, $50.00 in shipping, parts and labor per unit when you have to bring them in and refurbish them.
c) when you have shipped a sufficient number of units and got plenty of customer feedback, instead of the saleamans 'just' you can, possibly change to the cheaper parts.

Erik