Splat Board

1. Splat Daughter Board - September 2020
2. Overview - The General Principal
3. Schematic and Settings
4. Installing the Neo7 GPS Module
5. Add a Serial Console Port
6. Installing a Speaker
7. Antenna Recommendations
8. AToD packet Processing
9. The Anal3 Utility
10. Schematics

Splat Daughter Board - September 2020

In 2020 development has been sritched to the Splat board.

KiCAD CAD files are also on github for the Splat board.

Plug the Splat on to the STM32 it can be a bit tricky getting all the pins to line up causing it to skip a socket.

The latest firmware is archive my12 on github and we are using the newer STM32CubeIDE v14 (the latest) as the development platform these days. The STM board will also want to update its debugger firmware to the latest, and it needs that.

If you find the my12.bin binary file in the repo you can just copy that onto the STM board using the debugger's USB file share capability. It will take the file and then reprogram the board just by copying the file over. That way you don't even need the IDE.

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Overview - The General Principal

The Splat samples the RF input at about 2.7Mega samples per second into 12 bit values. When the algorithm detects that there is a transient in the sampled data it sends the packet off to the server so the server can look for coincident 'triggers' from multiple detectors. The server also knows the precise location of each detector, so it can work out the relative time of arrival of the same signal between detectors. And then it can work out where the signal (lightning) strike location.

Schematic and Settings

Installing the Neo7 GPS Module

Add a Serial Console Port

It is desirable to add the serial port console to assist in doagnosis and operation.

Solder two of jumper wires from the underside of the STM debug board's serial port to the floating jumper wire sockets that plug into the middle two pins marked 'SER' on the Splat board. With the Splat board in position there is not enough clearance to use jumper wires into the serial pins on the STM board.

The KiCAD CAD files are also on github for the Splat board. (You should already have the debug serial port connected across the STM board using jumper wires from the last incarnation of the project.

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Installing a Speaker

There is also a mini-speaker header which produces zapping sounds (PCM Synth from the onboard DAC) when the board triggers.

The speaker is connected to the header pins labeled LS1. The posative pin is on the righthand side. I installed an 8 ohm, 0.3 watt speaker.

Antenna Recommendations

Best results are from a HF antenna (switch over to it when not using the radio), but almost antenna will do - a simple dipole, or a simple dipole running along the curtain rail. Its terminated in 50R. Inside antennas are best to stop lightning getting into your shack however, sensitivity is well down for most inside antennas

You can use a 1:1 balun, but its not essential. The STM GND will go to the coax outer, but its really looking for a potential difference as an input so the 'dipole' could be one wire from the coax center as the shield will be at ground. The length isn't really important either. It can be a few meter to 6 meters on each side of the dipole.

A coax feed is best to wherever the antenna to prevent RFI noise entering detector as the antenna passes close to electronic equipment in the shack.

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AToD packet Processing

UDP Sample Packet:



Zoomed Display:

In this zoomed display, the green is the sample number and the purple is the DMA counter. The others are amplitude readings (mostly obsolete use these days in the Anal3 Utility).

Zoom of Transient:

Expanded around that transient it looks like this:



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The Anal3 Utility

This image shows how it simulates a strike (red cross) and where the detectors are located.



The Anal3 Utility's main purpose is to help with development and testing. That app can simulate a strike and generate the equivalent packets to send to the server and it can also read back the sampled data and display it, showing the Lat/Long of their locations.

Schematics