In this review I take a look at one of the newer members of the Khadas family; The Khadas Edge and Khadas Captain.
This board has some pretty interesting power management but, unfortunately, I saw the return of the magic smoke genie.
So, before I get started, there’s several things to note:
Firstly, full disclosure here; I normally purchase SBCs myself, but Khadas sent me review units of the Edge, Captain and also VIM2. However, like all my reviews, I say it, the way I see it.
Thirdly, this is a pre-release SBC, with an IndieGoGo campaign still running, so some things are a bit rusty and some things may change.
Unboxing the Khadas Edge
So, like my previous LattePanda and NanoPC-T4 reviews, I’ll have to have a Part 1, Part 2 and more than likely a Part 3, because there’s so much to cover on this particular SBC. This video I’ll be looking at all the low level stuff, GPIOs, chips used and overall design of the board.
The Khadas Edge comes as a small footprint SBC with an edge connector, allowing you to use it standalone, or with a base board. This makes it a fairly compact low profile board. Possibly taking the title of the thinnest.
The Edge - top side
So, first looking at the Edge, what do you get? Starting from the top right, working clockwise we have …
- USB2.0 connector
- PWM based FAN control
- reset button
- function button, which allows selecting boot mode
- power button
- 314 pin header giving you waaaay more GPIOs than any other SBC
- i-pex WiFi & Bluetooth connectors
- USB 3.0
- USB Type C
- HDMI 2.0
- Another USB Type C
- and a USB 2.0
- Then there’s 16GB eMMC
- 2GB RAM
- and the 6-core RK3399 SoC.
Top side ICs
Interestingly, the board can be powered from either of the USB Type C ports. Automatically switching between either of them.
16GB eMMC - KLMAG1JENB-B031
The Edge - dark side
The Captain top side
Moving on to the Captain, we have …
- User accessible button on the corner
- 40 pin GPIO header, which is absolutely NOT Pi compatible, for so many reasons.
- Reset button, which mirrors the one on the Edge.
- 12v DC jack
- SD card slot
- Some buttons to mash
- Display Port connector
- Touch panel interface
- Some more buttons
- Two MIPI-CSI and
- one MIPI-DSI connector
- Audio jack
- Function button mirroring the Edge.
- MXM3 edge connector
- Another user accessible button
- and GbE port
The Captain ICs
And splattered throughout the board we have a few interesting semiconductors.
The output is fully USB 2.0, 3.0 and Type C PD compatible and has all the usual protection circuitry you’d expect these days. You can select the DC buck oscillator frequency from 800kHz to 1.2MHz, but gathering from the 2.2uH inductor it’s running at 800kHz.
As we’ll find out later, it’s also fully visible on the I2C bus.
The Captain - dark side
Flipping over to the underside, we have
- An external speaker and MIC input connector.
- A nice M.2 slot, which is starting to be critical on SBCs these days.
- And LiPo battery connector.
In terms of semis, we have:
So, all up, it’s a pretty interesting SBC, but let’s see what it can actually do.
The RK3399 can get pretty hot under the collar when running all 6 cores, so a heat-sink is essential.
I’ll also be tracking power consumption using a handy power logger and also use a plain USB based SD card reader for some transfer tests.
Booting up was an interesting experience. Theoretically, I should be able to power the board from either of the USB ports or DC jack.
So, I’ll be powering the board from USB Type C instead.
Once powered up, the Edge booted straight into Android from the onboard eMMC.
Using my laser thermal sensor, showed up that the CPU temperature was being kept around 52C with the hottest part being the GbE transceiver.
So, like all my other RK3399 based SBC reviews, you definitely need some active or passive cooling for this SoC. Time for my Uber heat-sink.
Upgrading to Linux
So, on to upgrading the SBC to Linux.
To re-flash the firmware you have to put the SBC into upgrade mode. There’s several ways of doing this.
You can press and hold the function key while pressing the reset button.
Or via the debug serial port.
From the Linux command line.
Pressing the Function button three times within 2 seconds of boot.
Or short-circuit two pads on the board while pressing the reset button.Once you enter upgrade mode, the power light turns blue and starts to flash.
However, while the Edge was connected to the main board I never got the first method to work.
The second, third and fifth methods were also unavailable as you can only get to the M-register pads and serial port from underneath which you can’t get to when attached to the Captain.
The fourth method, (pressing the Function button three times within 2 seconds of boot), seemed to be the most reliable and you should see the upgrade screen appear.
I first tried to upgrade using the SD card method as this was the easiest. Khadas have some pretty decent documentation on how to do this.
So, I decided to upgrade over USB Type C instead of SD card using a Linux notebook.
I pulled the git repo, and since I had Debian and not Ubuntu a bit of fiddling fixed the install script.
I used the LattePanda power pack to power the Edge via one of the USB Type C connectors but as soon as I plugged in the second Type C port to my notebook, the gentle sound of electronics frying could be heard.
Anyway, so I then disconnected the board from the LattePanda power supply and powered it directly from the USB port on a Windows notebook.
Once booted I started to poke around to see what was available on the default image.
Like all my other SBC reviews I set the CPU scaling governor to performance mode.
The 128G NVME SSD was visible, along with the eMMC.
Linux GPIO tests
On to GPIO tests.
Looking at the schematic and probing around a bit I managed to figure out that the following I2C device map.
- I2C4 / I2C_SDA_PMIC (/i2c@ff3d0000) - 0x1B U - (/i2c@ff3d0000/pmic@1b) - 0x22 U - FUSB302B MPX (/i2c@ff3d0000/fusb30x@22) - 0x40 U - (/i2c@ff3d0000/syr827@40) U7 - 0x41 U - (/i2c@ff3d0000/syr828@41) U8 - I2C8 (/i2c@ff3e0000) - 0x18 A - STM8S - 0x22 U - FUSB302B MPX (/i2c@ff3e0000/fusb30x@22) - 0x39 A - APDS9960 - 0x62 A - CW2013CAS0 - 0x6B A - BQ25703A - I2C9 (/hdmi@ff940000/ports) - I2C10 (/dp@fec00000/ports)
The ones marked ‘U’ are unavailable for the user and have a Linux kernel driver accessing them. Based on the schematic I’m missing two more I2C devices. The audio CODEC and IMU.
Since there are actually 9 I2C buses on this SoC. I enabled a couple that I guessed were the right ones using the Device Tree Compiler.
- I2C0 (/i2c@ff3c0000) - disabled - I2C1 (/i2c@ff110000) - 0x1A A - ALC5651 (Enable I2C) - I2C2 (/i2c@ff120000) - disabled - I2C3 (/i2c@ff130000) - disabled - I2C4 / I2C_SDA_PMIC (/i2c@ff3d0000) - 0x1B U - (/i2c@ff3d0000/pmic@1b) - 0x22 U - FUSB302B MPX (/i2c@ff3d0000/fusb30x@22) - 0x40 U - (/i2c@ff3d0000/syr827@40) U7 - 0x41 U - (/i2c@ff3d0000/syr828@41) U8 - I2C5 (/i2c@ff140000) - disabled - I2C6 (/i2c@ff150000) - disabled - I2C7 (/i2c@ff160000) - 0x68 A - ICM-20602 (Enable I2C) - I2C8 (/i2c@ff3e0000) - 0x18 A - STM8S - 0x22 U - FUSB302B MPX (/i2c@ff3e0000/fusb30x@22) - 0x39 A - APDS9960 - 0x62 A - CW2013CAS0 - 0x6B A - BQ25703A - I2C9 (/hdmi@ff940000/ports) - I2C10 (/dp@fec00000/ports)
And now bus 1 and 7 have the two remaining devices.
i2cdetect -y 7 i2cdump -y 7 0x68 i2cset -y 7 0x68 0x6b 0 i2cget -y 7 0x68 0x6b i2cdump -y 7 0x68 while true do (i2cget -y 7 0x68 0x41 b; i2cget -y 7 0x68 0x42 b) | /root/h2d echo sleep 1 done
I set a few registers to enable the IMU and was able to query the temperature fairly easily.
GPIO tests were also successful and the GPIOs run at 3.3v. I’m not sure if they are 5v tolerant though. I wasn’t able to test out the infra-red as there’s currently no documentation on how to get to it.
As expected, Ethernet speeds were pretty decent with 937 Mbit/s on TCP throughput and .430 mS UDP jitter.
Unfortunately, I wasn’t able to test any further because of the magic smoke genie escaping from my notebook and only just started to install all the software for the Phoronix tests.
So, what do I think of the new Khadas Edge and Captain?
If you are worried about whether the product actually exists or not on the IndieGoGo campaign, well I can say it… does.
It’s still early days, but from what I’ve seen so far, they’re set to make a pretty decent product.
If you get the correct heat-sink, then both the Edge and Edge-V come in a fairly small package.
It’s good to see that they have designed in some decent power management, which was one of my suggestions I made to them. USB Type C is very quickly being adopted and will solve all the power related issues we have been seeing in SBCs so far. Even though it’s slightly more complex to implement, it gives you a more stable DC supply.
So, to SBC manufacturers reading. Start using USB Type C for power.