Spark

Spark.io support
This is an issue with Firmata in general. When servo support was first added the number of pins supporting Servo (via the Servo library) was equal to the number of Arduino pins supporting servo. This is no longer the case (and has not been for a few years). MAX_SERVOS is defined in the servo library and is determined by the number of timers available and the number of servos supported by each timer.