The following discussion focuses on some language differences from the BS2 due to the increased speed of the BS2SX.
The BS2SX is 2.5 times faster than the BS2. This can clearly be an advantage. But, on the flip side there are however a couple of penalties. One is increased power dissipation and the other is changes in BS2 commands which involve time sensitive tasks.
There is a wealth of literature relating to the BS2. Life for a newcomer to the wonderful world of Stamps can be very confusing and these minor language changes may add a bit to the confusion. Thus, I am inclined to recommend the BS2 to a newcomer.
But for the experienced user, this shouldn't pose much of a problem. Simply recall that the BS2SX is running at 2.5 times the speed of the BS2.
1/9600 = 104 usecs bit time 104 - 20 usecs = 84 usecsWith the BS2SX, the 20 usec overhead is reduced to 20/2.5 = 8. But, the bit timing is now 2.5 times faster. Thus, for 9600 baud, the timing is specified as 252.
1/9600 * 2.5 = 260 260 - 8 = 252
Note that there may be some disadvantages here. For example, for the PULSIN and PULSOUT, the resolution is improved, but the upper limit is reduced by a factor of 2.5. The upper limit with the BS2 is 65,534 * 2 usecs = 131 msecs. For the BS2SX, this is reduced by a factor of 2.5 to 52.4 msecs.
I assume the frequency of the PWM function is running at 2.5 times that of the BS2. This may cause problems when driving such "H" bridge configurations as the L293 and L298 to control a DC motor. I have yet to look at this.