@David I saw your cry for help on the Open Hours. There is so much misinformation floating around about the Sensors board about such simple topics that should just work but don’t. Here’s the deal:
The Arduino defines certain numbered digital and analog which don’t necessarily correspond to obvious numbering on a connector, and don’t correspond to MCU pins. For a reference to those pins, google for an Arduino Uno schematic. Essentially Arduino pins 0-7 correspond to Sensor board P2 pins 1-8, and Arduino pins 8-13 correspond to Sensor board P3 pins 1-6.
The servo sweep sketch defaults to using Arduino “pin 9”. The Uno schematic will show you this as pin 2 on connector IOH, and it’s connected to signal PB1. So on the Sensor board that’s P3 pin 2, and the schematic shows that as PB1 (correct). OK, does signal PB1 appear on any of the Grove connectors? I don’t see such a connection.
Maybe you could change the sketch to use a different digital output pin? OK, it needs to be a pin that supports PWM, which is a particular way of using certain timers, (to operate the servo). Arduino PCB silk screen has a ~ tilde symbol next to pins that can do PWM, and that’s pins 3, 5, 6, 9, 10, 11, which corresponds to PD3, 5, 6 and PB1, 2, 3 respectively.
So, you could for example use PD5, Arduino pin 5, aka P2 pin 6, aka Grove D4 pin 2. (I note in passing that oddly PD4, 5 and 6 appear on multiple different Grove connectors, whereas PB1-6 signals don’t appear on any.)
Now, when you run a hobby servo, usually it needs three wires, ground, servo-style PWM signal (nominally 5V logic levels), and a positive voltage of 5V to 6V (unless it’s a 12V servo etc). You may be tempted to power the servo off the VIO power pin on the grove connector. This is a bad idea – servos take a surprising amount of current when changing position, easily surging into the 100’s of mA even for small servos. Sensor board VIO comes from the +5V rail, supplied from the 96Boards LS connector, so from the Dragonboard and its 5V regulator that was not designed to supply a large current. The outcome is that moving the servo may easily result in a reboot of either the ATMEGA or the Dragonboard. So, figure on providing an external supply to the servo (ground in common with the Sensor board and Dragonboard, +5V or +6V direct to the servo.
Note that I’m looking at the Sensor schematic available here: http://www.96boards.org/products/mezzanine/grove-starter-kit, and dated 2015-11-29. I know there have been changes, and it would help if someone would post some links to updates.
And if someone updates the Sensor schematic, please add Arduino pin numbers alongside the the Arduino connectors on the schematic.