I got an e-ink display... And another... And another...
2022-12-04T23:04:04+00:00 • goncalomb • esl, e-ink
For some time I've been running a Saved Search on eBay for "electronic shelf labels" (ESL), these are those electronic price tags that you see in some stores, they used to be LCD but the newer models use e-ink displays.
In the back of my mind, I knew that these devices can be hacked and repurposed for other projects. I've seen some of those projects around the web.
A couple of weeks ago the search got a hit. There were some offers from Germany at 2€ per tag (used). I could not let it go, after researching a bit about these specific models, I ended up buying 100 tags in 2 sizes. Normally you can't buy these tags for less than 10€ each (new) and I think those are mostly Chinese samples, these devices are supposed to be bought in bulk by companies/stores.
These are very nice, most are in very good condition and show little signs of wear. Of course, me being me, I checked the seller again and he still had one last set of 50 of the larger size... Yes, I bought them! Am I crazy? I don't even have a project to do with them! I guess I'm writing this post to at least offset some of the buyer's remorse.
Here are the details:
- SOLUM ST-GR29000 (69x31mm display)
(FCC ID on label: 2AFWN-ST-GM29XX2N, similar: E2X-ST-GR2900N)
- SOLUM ST-GR16000 (28x28mm display)
(FCC ID on label: 2AFWN-ST-GM16XX2(N?), similar: 2AFWN-ST-GR1600N)
Here are the "user manuals" from FCC: ST-GR2900N and ST-GR1600N (these are not from the FCC ID on the label, they are from the 'similar' link above). These models have NFC, mine don't, but their "manual" is more complete
When exploring these kinds of things I always smile at the big CONFIDENTIAL watermarks on all the PDFs, it just means that you have the juicy stuff. Not the boring marketing brochure.
According to the manuals, the small diamond on the screen means that the "tag failed to locate GW" (gateway), that's expected. I don't have a gateway. Here are the official gateways to control the tags.
As a side note, all the tags that I bought include batteries, CR2450 (2 on the larger model). That's a good thing because the batteries would cost almost as much as the devices, in small quantities. I tested some of the batteries and they seem fine. These are very low-power devices, they only require energy when changing the screen (e-ink displays don't use energy to keep the same image on screen). According to the manual, they last 5 years at 1 update per day.
That's about all the original research I did about the devices themselves.
Standing on the shoulders of others
Before committing to buying them, I did some extra research on what kinds of projects people are doing with these tags and how open/hacked they really are. So the final purpose of this post is just to link to those other projects because they are the best source of knowledge on this topic.
Some projects just discard the electronics and reuse the e-ink display by connecting it to an Arduino/ESP micro-controller board:
But the really cool thing is reusing the whole device. Here's a guy that reverse-engineered the whole thing and wrote custom firmware for the tags:
This awesome work spun up some other projects that rely on this custom firmware:
And here are some other projects that use a different brand of ESL (Hanshow).
Overall, @atc1441 on GitHub has done a lot of hacking with these tags:
I don't really have a project to do with the tags at the moment. I do have some CC2531 boards that can be used to talk with the custom firmware (802.15.4, see links above), so I think reusing the microcontroller and electronics is the way to go if the goal is just to create some information displays. I'll start with that. Ultimately I would like to have a system to automatically update the tags, maybe even using MQTT or Home Assistant, but that is far in the future.