[HN Gopher] Show HN: A high-altitude low-power flight computer f...
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Show HN: A high-altitude low-power flight computer for high-
altitude balloons
I've been working on this for a while now, and I'm happy to share!
I've been into launching weather balloons for a few years. One
aspect of the hobby that really drew me in was the tracking side of
things. Tracking systems let you follow the balloon's position
throughout the flight and, most importantly, know exactly where it
lands so you can recover the instrumentation. APRS is what I
started out using during my first few years in the hobby, after I
got my amateur radio license in 2020 (W0MXX). I designed a few
small boards using the trackuino
(https://github.com/trackuino/trackuino) firmware (while breaking 3
$70 radio modules along the way). I then got into recovering
radiosondes, which are launched twice per day by the NWS and can be
reprogrammed using RS41ng
(https://github.com/mikaelnousiainen/RS41ng) to run many amateur
radio tracking protocols. I was a bit dissatisfied with how large
and heavy the radiosonde trackers were, so I designed my own
tracking system, called Tiny4FSK. Tiny4FSK is a flight computer
with built-in tracking using the Horus Binary v2 tracking system.
This protocol was developed by the Project Horus team specifically
for high-altitude balloons, and it brings features like high
transmit rates, forward error correction, and excellent weak-signal
performance in an open source package. It's designed to be as
compact as possible and can run on a single AA battery for upwards
of 17 hours. The main board comes with header rows that allow for
out-of-the-box expansion. I developed a shield that supports the
BME280 environmental sensor, the ICM-20948 9-axis IMU, and more via
the Qwiic connector. It also features an OLED display for basic
diagnostics. While I've pretty much polished the main tracking
procedures (and have tested on multiple flights), I'm still
developing the IMU code using a lightweight Kalman filter.
Additionally, there isn't yet a wide network of Horus Binary
decoding stations like the APRS network has (I-gates), but I hope
that by promoting this protocol, more stations will pop up. This
means that if you're not in an area with many receive stations,
you'll need to set up your own using either Horus-GUI
(https://github.com/projecthorus/horus-gui) or horusdemodlib
(https://github.com/projecthorus/horusdemodlib). One issue I'm
still working on is improving RF signal strength. Although the
protocol is decodable in very low-noise environments, the transmit
power appears to be lower than that of a typical radiosonde. This
could be due to several factors: limited current on a weak power
source (signal is stronger when powered from a bench supply), off-
tuned filtering/matching, or not paying enough attention to the
antenna. I'm planning to run more simulations to figure this out.
That said, the signal is still decodable from the ground even at
max altitude (~100,000 feet). On the more technical side, Tiny4FSK
uses: - the SAMD21 microcontroller, which is an ARM Cortex-M0+ MCU
- the TPS61200 boost converter, which is adjusted to output 3.3v -
Si4063 radio module, which I use on the 70cm band - ATGM336H gps
module - pretty cheap GPS module which works in airborne mode
(>18km) - integrated BME280 temperature, pressure, and humidity
sensor The code uses the Arduino framework to make it accessible to
beginners. All flights using Horus Binary v2, including
reprogrammed radiosondes, other custom trackers, and Tiny4FSK show
up in real-time on Sondehub Amateur (https://amateur.sondehub.org).
Flight data can be found in the /Media/Data folder on Github
(there's several missing flights on there though). Thanks for
reading, hope I didn't mess anything up too badly in the post! -Max
Author : mpkendall
Score : 32 points
Date : 2025-07-30 14:51 UTC (8 hours ago)
(HTM) web link (github.com)
(TXT) w3m dump (github.com)
| paulgerhardt wrote:
| Love this. Have a friend that regularly sends $30 balloons a few
| times around the world. They routinely end up over interesting
| areas like hot spots in the Middle East or North Korea. Would be
| great to issue commands to a light weight camera but the
| bandwidth is so limited - payload is a factor too - can only be
| under 100 grams or so. Bandwidth is in the order of 30 bytes per
| minute. Would be fun to take picture remotely and then drop the
| payload/memory card when the balloon circled back to friendlier
| territory.
| yonatan8070 wrote:
| When it flies over these unsafe areas, isn't it detected by the
| region's air defense systems and shot down? Or are these too
| small and high to be seen by such systems?
| 0_____0 wrote:
| Even if it made sense to try to take out a balloon, the
| missiles that can reach 80,000ft+ are tens of million dollars
| a piece, and not that many countries have access to that type
| of missile tech.
| Catbert59 wrote:
| Interesting!
|
| I'm thinking of building a small PCB for ballooning too.
|
| But I most likely will shift the design decisions a bit:
|
| - 2.4GHz LoRa for high-rate telemetry as reciving can recycle
| Wifi-Antenna gear. The Semtech SX128x chips are easy to handle.
|
| - Low rate telemetry on 433MHz with a SX12xx or SX17xx.
|
| In terms of chips most likely something around the STM32U series.
|
| The company ePeas has very interesting energy harvesters. Not
| super cheap - but still affordable. They have special profiles
| for supercaps which are very resistant against freezing.
| mpkendall wrote:
| Hey! Yea I've been looking into energy harvesting a bit as well
| after watching this video:
| https://www.youtube.com/watch?v=TGbtzlWb-Kc
|
| Generally the higher frequency you go, the lower range you get
| as a rule of thumb. It's also harder to design around higher
| frequency boards, though it's totally doable. That said, I'd
| love to see how 2.4GHz works out!
| Catbert59 wrote:
| LoRa is absurdly robust.
|
| Someone maxed out the ranging mechanism of the Semtech SX1280
| with a 5dBi rubber antenna. He reached 60km with LoS. And
| there's a report of 90km in a ballooning project.
|
| (https://github.com/StuartsProjects/SX1280_Testing)
| mpkendall wrote:
| Interesting, thanks for sharing! I'm interested in creating
| some form of live video/image system, thanks for this!
| Catbert59 wrote:
| The Semtech modems have several modulation modes which
| can be configured in great detail.. the datasheet is
| quite verbose about them.
|
| The latest generation of chips (AFAIR not yet released)
| integrated a mode that allows them to receive on all LoRa
| speed grades in parallel. Bit like the existing LoRaWAN
| basestation ICs.
|
| I remember reading a datasheet that one (already released
| chip) is also able to work on 144-146MHz. But that's not
| what standard Asia (ESP32+LoRa modules) offer. TTGO has
| AFAIR recently released a super new board that allows
| this band.
| jotux wrote:
| In a previous job I pushed an STM32WL5 on a custom
| frequency over a private satellite constellation with a
| relatively large yagi antenna. Over 70k km round trip :D
| yonatan8070 wrote:
| In fact, it's so robust that even when your antenna is a
| piece of wire hanging off a GPIO of a microcontroller with
| absolutely no dedicated radio hardware, you can still get
| several km of range. Truly crazy stuff.
|
| https://youtu.be/eIdHBDSQHyw
| jotux wrote:
| If you're going to use LoRa with an STM32, consider the
| STM32WL5x. It's an ST32L4 with an integrated SX12xx.
| Catbert59 wrote:
| I have at least 10 of them in my lab :-) Thanks for the hint!
| prpl wrote:
| looks like a bunch of NEWBS.
|
| (guessing github.com/NEWBS was taken)
| normaldotcom wrote:
| Awesome to see HAB on hacker news! Was following some of your
| development years ago when I developed a small APRS tracker, have
| been meaning to revisit that project someday. Also developed a
| WSPR version that I haven't published any info on, but had a
| great trans-atlantic flight with that one. Keep up the great
| work!
|
| http://protofusion.org/wordpress/2015/10/featherhab-2-gram-h...
|
| http://protofusion.org/wordpress/2016/02/featherhab-source-c...
| hazek112 wrote:
| How'd you maintain connection over the ocean?
| dylan604 wrote:
| I did one of these balloon launches myself several years ago, and
| attempted to build a flight computer myself with Arduino and
| multiple sensors. I could not find an efficient way to read all
| of the data from the selection of sensors in the limited memory,
| so I wound up using a Mega. Nobody involved was a licensed radio
| operator, so our live tracking was very primitive. It wasn't
| until after 45k' that we realized our GPS tracking stopped
| tracking at that altitude because why would a civilian be at that
| altitude. Of course we didn't know that until researching it
| after recovery, but we were very relieved when it started to
| updating once it came back under 45k'. Unfortunately, something
| happened (my coding to be sure) that caused the log to not be
| written as expected. Was hoping to be able to compare the GPS of
| the actual flight against the forecast model we used. This is the
| very thing I would have loved to have for future launches. I even
| made friends with a licensed operator to make it legit. (couldn't
| be bothered to take the test myself)
|
| One thing to keep in mind for anyone wanting to do their first
| one. If you go to the trouble of printing up contact info for an
| "If Found", don't forget to attach it before lift off like I did.
| guywithahat wrote:
| You should check out Sceye, they're hiring and doing this.
| Unfortunately you have to live in the middle of the desert in New
| Mexico, otherwise it's a cool company
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(page generated 2025-07-30 23:01 UTC)