Catching Data from the Edge of Space

Your weather balloon is 30 kilometres up, transmitting GPS coordinates, temperature, and pressure readings every two seconds over APRS. But your ground station is overwhelmed—packets arrive faster than your logging system can write them to disk, and your memory is filling up. You need the most recent data, not a system crash.

This is where ring buffers shine. Born in the embedded systems boom of the 1980s, they solve a fundamental problem: how do you store a continuous stream of data when you don’t know how much space you’ll need, but you know you only care about the most recent samples?

The Go Ground Station

type TelemetryRing struct {
    data   []string
    head   int
    full   bool
}

func (r *TelemetryRing) Add(packet string) {
    r.data[r.head] = packet
    r.head = (r.head + 1) % len(r.data)
    if r.head == 0 { r.full = true }
}

func (r *TelemetryRing) Latest() []string {
    if !r.full { return r.data[:r.head] }
    return append(r.data[r.head:], r.data[:r.head]...)
}

The Lua Flight Computer

local ring = { data = {}, head = 1, size = 100 }

function ring:add(reading)
    self.data[self.head] = reading
    self.head = (self.head % self.size) + 1
end

function ring:get_last(n)
    local result = {}
    for i = 1, math.min(n, #self.data) do
        local idx = ((self.head - i - 1) % self.size) + 1
        table.insert(result, self.data[idx])
    end
    return result
end

ring:add("packet-A")
ring:add("packet-B")
ring:add("packet-C")
print(table.concat(ring:get_last(2), ", "))

Go’s approach uses a boolean flag to track when the buffer wraps, making the “get all recent data” operation clean but requiring extra state. Lua’s version stays minimal—perfect for the microcontroller aboard the balloon itself—trading some complexity in the retrieval logic for simplicity in the core structure.

Both solve the same elegant problem: when your balloon disappears behind a mountain or your radio hiccups, you haven’t lost everything. You’ve got a perfect circular snapshot of the most recent telemetry, automatically discarding the oldest data to make room for the new. It’s the computing equivalent of a flight data recorder—simple, reliable, and absolutely essential when you’re tracking something 100,000 feet above your head.