This is a pair of dev boards designed to provide a local stratum 1 GPS based NTP server.

• ESP32-S3-MINI-N4-R2 (Dual CPU, 4M flash, 2M RAM)
• 10/100 Ethernet
• PoE, but can also be powerd by USB-C or DC 5V-28V
• 12 LEDs showing GPS status (number of sats on each network and PPS blink)
• L86 GPS module, with CR2032 battery holder (CR2032 recommended)
• WAGO connectors for connecting cable from main module to GPS

The power supply flexibility is also a key feature, either DC 5V-28V, or USB-C, or PoE. PoE requires the Ag9912-LP module (optional extra).

The 12 LEDs are WS2812, and the supplied code shows them lit in sequence, blue for NAVSTAR(GPS), red for GLONASS, and green for GALILEO, with one LED for each 2 active satellites in use (half brightness for final odd number). The last LED blinks yellow for each PPS on the second.

Unlike some GPS devices, which have a coax to a patch antenna, the GPS module connects via 5 cores to the main board, allowing it to be placed outside. Solid core cat5 cabling works, but screened cable may be better in some cases. Cable can easily run several metres. You should ensure the GPS module has a good view of the sky for best results. For outside placement we find these work well https://weatherspares.co.uk/products/ecowitt-rs0001-sensor-shelter

This a fraction of the price of typical commercial GPS NTP servers. These commerical units claim 100,000 requests a second, where as we may well be lower. This board is around 0.1ms latency usually, and total requests per second seems to be several thousand. A typical, even large, business, would not have any where near that many requests per second, so this is ideal as a business time server, but not so much as a high volume NTP pool server. Of course this could work as the main reference for a device that operates as a stratum 2 server, such as a FireBrick, and provide high levels of requests per second.

Supplied with resin 3D printed case for board and for GPS module. You'll need a lead, and solid cat5 is a good choice. Note the resin case will yellow in sunlight.

MQTT reporting shows status, PPS reliability, requests per second, location, etc.

Tips

GPS

The GPS module needs a CR2032 battery to work. Later boards have pads marked "No bat" that can be bridged to operate with no battery. A battery is recommended else startup takes a long time to get a lock.

The GPS module should be placed facing up, not sideways, for best results. A good view of the sky is recommended, but it will generally work fine on the side of a building.

The resin case is not waterproof - you could apply a coating such as acrylic spray on the PCB, or better still enclose in a suitably sealed plastic box. It can often work inside a window or inside a loft under the roof tiles.

See the status web page shows details of number of satellites in use.

PoE

The PoE module is optional. When soldering to the board check pin 1 carefully. It has a small 1 mark on top of module, and PCB has a 1 by pin 1.

PoE requires a current draw to stay powered. Some switches are happy with lower current, so try turning off the ethpoepwm - if that works it saves power.

Without PoE you need separate power, DC or USB-C.

Ethernet

The device can use WIFi and Ethernet. The Ethernet works with or without PoE.

Normal working operates Ethenet as a full network interface allowing access to the web control pages, MQTT, etc. Response times for NTP are around 2ms.

However, you can set gpslowlatency which switches the module to a special NTP only Ethernet working. This starts after 2 minutes and when there is a GPS lock. In this mode normal Ethenet working is suspended, so you will have to use WiFi to access control pages, MQTT, etc. The IPv4/IPv6 are frozen, so recommended to use fixed IP config if your DHCPserver would be upset by IP used after expiry. However the NTP latency drops to around 0.1ms.

All parcels shipped with tracked shipping, usually shipped within one working day. If you find a large order has no shipping to EU, try placing smaller orders under €150.