Hardware A8 GPS
Some iot-lab nodes are equipped with a A8 open node with the GPS option:
- 165 nodes on Saclay site (all open-a8 nodes)
- 32 nodes on Grenoble site (open-a8 list)
Both sites are equipped with an internal repeater GPS antenna. The GPS signal reception on each node allows using the GPS clock as a precise time synchronization mechanism.
- The board GPS receiver is the MAX-6Q
- The indoor GPS repeater is the Hanger Re-Radiating Kit - HNRRKIT (Used in Grenoble)
Usage for timing
The M3 control node and the A8-M3 associated to the A8 open node can read by interruption the GPS PPS (Pulse Per Second) signal. This PPS acquisition can be used to counterbalance the clock M3 drift very accurately each second.
This local precise A8-M3 timer can be initialized by Open A8 NTP time (Network Time Protocol) through the uart link, or by using the control node unix time through the i2c link.
An example is provided allowing a GPS Synced Sniffer on A8 open-nodes. It used open-a8 nodes GPS to precisely time sniffed radio packet.
The hardware architecture diagram :