Modos Color Monitor Pushes E-Paper Displays Further

Last fall, Modos debuted the Paper Monitor and Dev Kit, an open-source e-paper display kit that hit a record 75-hertz refresh rate. The project was successful, raising almost double its US $110,000 goal.

Now the two-person startup is back fundraising for Modos Flow, a 13.3-inch color e-paper monitor with a higher native resolution of 3,200 x 2,400, touch input, and a 60-Hz refresh rate, which is made possible by a new display controller called Enchanter.

With the Flow’s crowdfunding campaign now live on Crowd Supply, cofounders Alexander Soto and Wenting Zhang spoke with IEEE Spectrum about the engineering behind it and the lessons they’ve learned on their crowdfunding journey.

This conversation has been edited and condensed for clarity.

What is the Modos Flow, and how does it improve on the Paper Monitor Dev Kit?

Wenting Zhang: The previous Paper Dev Kit is a DIY kit. You get the screen and the board, but nothing else. You add your own shell or embed it in another project. A lot of people connect it to a Raspberry Pi, for example.

The Modos Flow is a complete monitor. The only port is USB Type-C, so you’re supposed to connect it to a laptop or PC.

The Flow’s higher resolution is enabled by a new open-source display controller board called Enchanter. What’s changed?

Zhang: The new board has a larger, newer FPGA [field-programmable gate array], has double the DDR3 memory bandwidth, and a power supply that delivers higher currents for the more power-hungry screen.

But mostly, it’s about the display input. The input decoder chip is a Chrontel CH7516 DisplayPort-to-LVDS converter. It supports DisplayPort 1.1 rather than 1.0, enabling higher resolutions.

We want the whole thing open source, so all our parts need to have open documentation with nothing gated behind an NDA [non-disclosure agreement]. This chip wasn’t available when we launched the Paper Dev Kit campaign, so we had no way to support DisplayPort 1.1 while keeping things open. The new chip made DisplayPort 1.1 possible

A common skepticism about e-paper monitors is that faster refresh rates don’t matter if pixel response is still slow. What’s your response?

Zhang: It depends on how you measure it. On LCDs, we measure how long a pixel takes to go from 10 percent to 90 percent of its target brightness. Measured that way, the older E Ink screens on Glider come in around 100 milliseconds. The latest screen, shipping with Enchanter, is more or less 50 milliseconds.

That’s still slower than an LCD, but the first-generation iPad shipped with an IPS screen with a response time around 30 milliseconds. If people were okay with that, 50 isn’t far off.

Also, 10-to-90 percent isn’t a fair perceptual metric. When you move the mouse, what you feel as latency isn’t the pixel fully changing, but when it starts changing. That’s what we optimize for. A higher frame rate shortens time spent buffering, and our controller adds no buffering of its own, so we can minimize the time from user input to onscreen response.

You’ve now taken two products through crowdfunded manufacturing. What were the biggest challenges?

Alexander Soto: The initial plan never goes the way you think. There are always factors outside your control. A chip crisis, tariffs, manufacturing delays. The Flow’s display bezel uses a very specific color-mixing solution, for example, and it took about a month to get that one shade of white just right.

Zhang: Manufacturing, even at a smaller scale, is hard. Factories do exactly what you tell them, and when anything is a tiny bit off, they halt and wait for input.

For example, with the 6-inch model of our prior project, our initial 100 samples were all good, so our instructions for the next batch didn’t include testing the screens. Then we ordered 500 for mass production, and 300 were defective. When we discovered this, we had to tear down 300 assembled units. I tested more than 300 panels myself.

I learned it’s important to be close to the factory or to hire someone local. I used to think it’s as simple as sending an order to the factory online and the parts just get delivered. It never works like that.

Soto: Also, to add to that, reduce your scope and increase your timeline. When we came to doing Enchanter, we thought, “Yeah, we can get this going in a few months.” But it took eight months, even though we already had the prototype. Whatever your gut feeling is on the time it will take, double it.

Why keep going down this path rather than seeking investment?

Soto: I think I’m just stubborn [laughs]. But really, I’m happiest seeing someone hack the dev kit. One community member went from knowing nothing about PCBs [printed circuit boards] or FPGAs [field-programmable gate arrays] to building a board from scratch and retrofitting it into a laptop within a year. We’re seeding a community where each person has their own ideas to build.

Zhang: We discussed both investment and collaborating with established companies, but neither went through. We’re too small to win against a bigger company, and the e-paper monitor market is also just small.

From an investor’s perspective, there isn’t enough money to be earned. They value our engineering capability but they’d rather direct us to do something else. But that’s not what we want to do.

What’s your advice for engineers considering a crowdfunded project?

Soto: Build community. Before our first campaign, we spent a year attending conferences, writing posts, and sharing our work. It’s good to have people who know you, who’ve shaken your hand and tried the product. You can’t engineer in a silo.

Zhang: If you have the idea and think it could work, just do it. I have way too many prototypes I didn’t continue, and other people turned the same idea into a product, which in many cases seemed worse than my prototype. Yet they were successful. Don’t make yourself regret the things you didn’t do.