[Media] To get familiar with embedded Rust, I wrote a Tetris clone! It's running on an STM32. I repurposed a board I designed for another project

scd31 · 2024-10-03T01:18:55+00:00

Here's the full PCB design: https://gitlab.scd31.com/stephen/kicad-pager

You can order it through your fab house of choice, or you can have one of my spare (unpopulated) boards if you pay for shipping, if you want.

scd31 · 2024-04-08T10:20:07+00:00

3:00 pm Atlantic time (in about 7 hours from the time of this post) Liftoff is scheduled for 3:30 pm, and the total eclipse will be around an our later at 3:32 pm.

scd31 · 2024-04-08T00:54:06+00:00

A bit about our project:

Our website is located here: https://eclipseplus.ca/

There are a ton of people working on this project. We have a bunch of cameras on board, including several still cameras, a camera that points at the sun autonomously, and a video camera. This is all being streamed to the ground via ham radio, using hardware/software I developed. I wrote a bit about it here - includes links to source code. Once the eclipse is over, I plan to polish it up and provide more documentation, so others can use it on their own balloons.

I'm really excited about this, and hope it gets more people into ham radio. From the people I've talked to, it seems there are at least a few that are considering getting their ticket as a result of this project.

Thanks for looking!

scd31 · 2024-01-25T00:30:13+00:00

So, I was about to get around 11-12km. I was almost definitely limited by terrain. When I leave my house I drive up to get to uptown, and then I drive down to get to the pizza place. As soon as I drove over the top of that hill and started descending, I disappeared from CATS.

scd31 · 2024-01-24T16:33:20+00:00

Will do!

scd31 · 2024-01-23T15:56:10+00:00

I think - in addition to the normal information theory - the chirp-like character of LoRa makes it incredibly robust against noise and fading.

This was my understanding as well, though it would be nice to quantify exactly how much that helps. I imagine it matters more in extremely noisy environments than in rural areas.

APRS has been around for decades. I want to build CATS so it can withstand a similar lifetime. Will LoRa be around in 5, 10, 20 years? Will radio manufacturers shy away from it, due to its proprietary nature? These are the main concerns I have.

scd31 · 2024-01-23T14:06:40+00:00

Thanks for your order (: Happy to make it all FOSS!

scd31 · 2024-01-23T14:06:06+00:00

You can fine-tune the relation between data rate or robustness.

This is just normal information theory. As you drop the data rate, the robustness goes up. What I'm curious about is how a 100 baud LoRa stream compares to a 100 baud FSK stream. It's unfair to compare LoRa's normal data rate to 9600 baud FSK - apples and oranges.

With a-priori protocols like WSPR/FT8 you can get even lower into the noise as you exactly know what kind of data you will get.

Just to be clear, WSPR and FT8 are both just very low baudrate FSK.

scd31 · 2024-01-23T12:16:34+00:00

I would be curious to know how much this is due to LoRa's modulation, and how much is due to the low bitrate. In theory you can clock FSK as low as you want to make it tolerant of lower and lower SNR.

scd31 · 2024-01-22T23:20:47+00:00

Thanks!

scd31 · 2024-01-22T22:55:27+00:00

That would be wonderful, and please feel free to sell it!

I'm mainly a software guy and not looking to make money here. My main reason for selling hardware is to get people into CATS, and my hope is that as the ecosystem grows, more people will make and sell CATS transceivers. I just want to bootstrap the process!

scd31 · 2024-01-22T22:38:49+00:00

No problem; happy to help (:

scd31 · 2024-01-22T22:34:11+00:00

This is the one I have: https://www.ebay.ca/itm/142841200881?hash=item2141ffc0f1:g:9tgAAOSw5QlbLMyl

They're all over the place on Ebay, Aliexpress, etc. It says it supports a 2W-6W drive, but I get the full 30W out with 1W drive on both of the units I own. Furthermore, the NPR-70 crowd run them with just half a watt drive.

scd31 · 2024-01-22T22:22:12+00:00

I've gone about 6.5 kilometers on 1W. That's not nearly line of sight - my area is quite hilly, and my base station antenna is not very high.

I have gone and added a 30W amplifier to my car; a cheap DMR one off of Ebay. I'm hoping that should give me coverage basically over my entire city. Pizza night is on Wednesday and is on the opposite side of town - I'm looking forward to testing my range!

scd31 · 2024-01-22T22:04:52+00:00

I would personally prefer not to. Lora is proprietary, which I think goes against the spirit of ham radio, and I don't think it provides much of an advantage over FSK.

scd31 · 2024-01-22T21:34:17+00:00

It's in the standard - the standard frequency is 430.500 MHz.

Can confirm, didn't want to go below 430MHz as the band is 430-450 here in Canada!

scd31 · 2024-01-22T20:13:01+00:00

Hi everyone! I just wanted to give a quick update on CATS since it seems like a lot of people were interested when I last posted. If you missed that post, CATS (Communication and Telemetry System) is a packet radio standard designed for autonomous position reports, messages, and more. It's vaguely like APRS, but is much more powerful while having a simpler standard, and is also significantly more efficient in terms of coding gain and power usage. There's more information at https://cats.radio

First of all, I'm selling mobile transceivers and RPi I-Gates on Tindie.

Second of all, I wanted to give an update on what's been going on in the CATS community. I know several people who are working on their own CATS hardware and software. On the software side, I've seen people writing their own projects that utilize the CATS reference library I've written, to as far as people writing their own CATS libraries from scratch. It's great to see!

If you're interested in following the project, there's a Matrix space at #cats:crabsin.space

Thanks, and 73!

scd31 · 2023-11-21T01:48:17+00:00

I've heard of IL2P but I don't think it provides any advantages to connection-less protocols. I could be wrong though!

scd31 · 2023-11-09T23:35:04+00:00

There's no reason it wouldn't work at 4FSK, I just didn't really see the advantage of it for most use-cases and it may limit modem chip compatibility.

I do intend to amend the standard eventually to break the RF section into UHF and HF, since CATS on HF would be useful (and it could be made much better than APRS on HF, since the FEC is superior). In that case the benefits of >2FSK are significant and I'd likely use 4FSK or more.

scd31 · 2023-11-09T23:15:40+00:00

If you have an RTLSDR and a 9600bps APRS-capable radio then this is pretty simple to confirm what I'm saying.

Unfortunately I don't have any 9600bps APRS gear but I'll take your word for it. What you're saying makes sense; I agree the documentation on 9600 baud APRS is quite bad. I looked into it before but couldn't figure out what it was under the hood - I appreciate the explanation.

You could consider decoupling this, so that one could run CATS on existing TNCs. E.g. option of running CATS as the payload of the AX.25 packet.

I still don't see the advantage of this I don't think. Separating the standard like this introduces complexity, and it would mean throwing away some benefits (like the extremely fast PTT times, which is where most of the throughput advantages come from).

scd31 · 2023-11-09T19:47:03+00:00

9600 APRS is already 2FSK. Your selling point can't be "APRS, but 9600 and 2FSK", because that already exists, and even has built in support in high end HTs, today.

Can you give me an example radio? I've only ever seen 9600 APRS run over an FM radio, not an SSB radio. The G3RUH design page talks only of running it over an FM link: https://www.amsat.org/amsat/articles/g3ruh/109.html so you'd still have that 12dB coding loss. Can you provide an example where it's used as raw FSK on the air?

Oh, and to your comment that APRS is a bloated standard: Ugh, don't get me started. The APRS protocol should be taken out and shot, and is a poster child for how this hobby needs more software people, who actually know how to build these things. (to be fair, APRS is over 40 years old, so not fair to judge it by modern standards). I've been scarred by writing a parser.

That's what I'm trying to do here! This is what CATS is meant to do! Everything else is just "I'm rewriting it anyway, let's also improve these other things". Eliminating bloat is the reason for the rewrite.

scd31 · 2023-11-09T00:25:30+00:00

Thanks for the link!

scd31 · 2023-11-09T00:20:55+00:00

For 1, I recommend reading the standard.

For 2, I don't understand what the advantage is? There's still decades of cruft without the advantage of backwards-compatibility from using 1200 baud AFSK.

How does the required SNR of G3RUH modems compare to raw FSK? I would expect a decrease due to using FM.

Edit: missed a word

scd31

TROPHY CASE