A few additions to the great answers by pelrun (who is indeed a fellow user, but quite knowledgeable!):
- yes, power is only through the USB pport
- the serial port power is only used to power RX and TX voltage translators (BSS138 mosfet + 1M resistor to ground + 10K pullup), which then connect directly to inputs on the CPU. We do not have the exact figure either. Assume less than 1mA draw.
- the power management unit (voltage regulator) is an AXP223. Rated maximum input voltage under normal operation is 6.3V. Note that the fan is also directly connected to the input voltage. It is rated for 5V +/- 10% nominal. Brownout voltage is 4.4V. Again remember that the fan will start slowing down before that. To power from battery, we highly recommend either:
1) a USB power bank battery, you can get any size and shape you want and they deliver regulated 5V. Have a look here for some calculations and run time estimates with a 2600mAh power bank:
2) Or you could use either a step-up or a step-down voltage converter if you already have a battery for other reasons (e.g., in a robot), for example those tiny units:
Maximum we have ever achieved is 3.73W. Under the burn test JeVois module (which fully loads CPU, GPU, USB, camera, etc) you should see 3.5W, and other ArUco or other lighter modules, expect 2.5W.
Wireless streaming of video:
We have done it once using a $25 OpenWRT router. OpenWRT is an open source framework for routers. OpenWRT has USB camera support, and can stream video wirelessly using the mjpg-streamer OpenWRT module, see
You then simply use a Y-type cable to connect JeVois to the USB port of the OpenWRT box and to an additional power source (the USB port on the OpenWRT box is unlikely to be able to power JeVois). The OpenWRT box detects JeVois as a connected USB camera, and triggers the mjpg-streamer module. There is a bit of messing around with config files and options passed down to mjpg-streamer to select the correct resolution and you are good to go. You view the video by wirelessly connecting your tablet to the OpenWRT router (which acts as a wifi access point) and then pointing your browser to some URL (see the mjpg-streamer doc) where you will see the video from JeVois.
Try a search for "GL-MT300N" or similar. Although we have not used this exact model, it should work just fine since it has OpenWRT and also a USB2.0 port to which you can connect JeVois. Note that the CPU in these OpenWRT boxes is quite slow (e.g., 200MHz single core) so the framerate at which you will be able to see the video may be limited. We could do 15fps at 320x240 MJPG in our tests. Because of the slow OpenWRT CPU, you may be better off doing compression to MJPG on JeVois and streaming MJPG video out of JeVois, so that the OpenWRT box will just forward the video frames over wifi without the need to compress them on the OpenWRT CPU.
We have successfully used an Adafruit Feather 32u4 Bluefruit LE. We connected its serial pins to the serial port of JeVois, and wrote a trivial piece of code that would just forward serial data between the serial pins and the BLE module of the Feather. It worked well at 9600 bauds but choked at 115200. Looks like serial transmission over BLE is limited to 9600 bauds. Have a look in JEVOIS:/config/params.cfg for config options we used when transmitting serial data over Bluetooth. Other serial-to-BLE modules are available and should work fine as well, but we have not yet tested. The main drawback with the Feather 32u4 Bluefruit LE is its price ($30).