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- Jason is currently an engineer at CastAR, who now have 100+ people! They work out of a space called Playground Global, who were also their lead investor in their A round.
- Jason’s side projects are done under a brand called Reclaimer Labs.
- He also sells some of his projects on his Tindie store.
- Jason did a talk about LED drivers at an SF meetup a few months ago. (slides are here)
- The “Internet Window” has 25000 LEDs. Which apparently isn’t that hard, even at a resolution of 128 x 64 LEDs. At a 3 mm pitch on the LEDs, the display is roughly 1 x 2 ft wide.
- Most of his projects are connected via a Particle Photon.
- The LEDs draw 5V at 16A in a normal state (with PWM). The incoming power is at 24V.
- The “Internet of Thermocouples” was a weekend project to help his friend not have to go check the temperature on an induction over every couple hours.
- Lately Jason has been prolifically posting about USB C. His latest project is building an easy bake oven.
- The cables are “Electronically marked” and come in varying qualities online. There is a Google engineer who reviews USB C cables on amazon.
- Some of the high level capabilities of USB C we learned:
- The Super speed pins can do video
- It’s possible to easily deliver 15W (3A at 5V).
- The default is USB 2 high speed.
- The max speed of data is 10 Gbps x 4 lanes = 40 Gbps throughput.
- Power delivery communication
- USB developers page and download the zip files
- VESA runs the display port spec.
- Jason ported a library, which ended up being over 4000 lines of code. Google has open source code that was the basis of this project.
- They troubleshoot with a Lecroy T2C USB analyzer.
- The defaults don’t really need much:
- One extra resistor to use USB C without a PHY
- 5V @ 500 mA – USB 2 high speed
- Can watch that pin to see if it’s offering .5, 1.5 or 3 A
- Alternate modes
- Follow Jason on twitter as @AscendedDaniel. Check out his blog and projects at ReclaimerLabs.com. You can also follow his code on GitHub.
- They’re hiring at CastAR! Firmware, EE, others
Regarding the 30 ms update rate to make a VR realistic: this works only with enough persistence, like you know it from old analog scope phosphor persistence. I hope the castAR micro projectors have this. I didn’t believe it, but if you implement PWM for LEDs, even 100 Hz is not enough, you can see lots of moving dots when moving the eyes fast, especially at lower dim levels.
There was an interesting discussion about it on the EEVblog forum about this. Once I measured the PWM frequency of car headlights with long exposure photographing and it was only 100 Hz:
http://www.eevblog.com/forum/beginners/cheap-standalone-usb-microcontroller/msg1160888/#msg1160888
I don’t care much, but for some people that is very annoying. Studies show that you need at least 3 kHz PWM frequency to eliminate this effect for the human eye.