DJI / ZeroUAV hardware 3 in 1 technical review/teardown
I've had this stuff around for a while, but had no time to write stuff up.
So instead of letting the pics rot, I figured I might as well post it.
Hopefully some people find the info useful.
Here's some details about the ZeroUAV YS-X6 system:
Top side of main controller contains the LM2596 SimpleSwitcher DC/DC module for taking battery voltage down to 5V levels for the rest of electronics. Unlike DJI, Y6 MC communicates using RS232 - so there's a Maxim MAX3243 3/5 channel TTL>RS232 converter. The rest of components are passives/crystal/headers. Of interest is 3 FETs for driving RGB led strip near the bottom center of mainboard.
Bottom side is a bit more interesting, containing the main processor (Atmel AT91RM9200CJ), a 180MHz, 32-bit ARM920 MCU with 64Mbyte external SDRAM (HY57V64162) and 4Mbit Atmel DataFlash for firmware (AT45DB041D). There's also an Altera Cyclone EP1C3T100C8 FPGA, it's purpose isn't really obvious (at first I thought code / firmware protection but that's not the case), maybe it's used for PWM generation/capture. It could also be running the actual IMU fusion code, who knows. Anyway, it's there. It's loaded from Altera EPCS1N config flash, and driven my 50MHz oscillator. There's also an AD7997 10bit, 8 channel ADC with I2C bus, which is probably used for battery voltage monitoring (the ADC on AT91 must really suck).
Wifi module is just a breakout board for Rabbit Semiconductor Wificore module, which contains ST's STM32F103RE, some passives, TI switching DC/DC regulator, and a Maxim MAX3232 for RS232 conversion.
Moving on to IMU, it's another professionally-fabricated piece enclosed in metal cube and anti-vibration foam, but with the usual suspects for sensors.
There are 3 Analog Devices' ADXRS620 yaw-rate gyros, with 2 mounted on PCB standoffs (not as cool as DJI solution with facing into a metal cube, and harder to axis align etc, but shrug). All the analog sensors outputs are connected to ADI ADS1256T 24-bit ADC chip, which then outputs the data over SPI (and I suspect, IMU->MC connection is just SPI + power, but I have not checked this fully). This side also contains one of the dual-axis accelerometers from ADI again, ADXL203. A couple precision voltage references and some passives round up the top side of IMU cube.
Bottom side of IMU cube PCB contains standoffs for the 2 vertically-mounted ADXRS620 gyros, flat-mounted yaw rate gyro, as well as the second, also vertically mounted ADXL203. Freescale MPXH6115A pressure sensor is mounted facing into the cube, to protect from prop wash and wind, just like the DJI solution.
On to the GPS. Users have been reporting much better GPS performance with Y6 than DJI, this is likely due to very good shielding of the GPS module. It's probably same ublox-neo6 module as DJI GPS, but it's covered with another metal shield piece. The usual HMC5883L I2C digital compass is present, also with caps pretty far away from it, despite datasheet recommending otherwise.
What's interesting is lack of GPS backup battery (unless they moved it under the metal shield, which doens't really make sense).
Top side of GPS is pretty boring with just a large ceramic antenna.
ZeroUAV really cheaped out on the LED module, and simply connected a 5050 RGB led module to an extension cable. The driver FETs are inside the MC, but this also means users can hookup LED strips or similar directly to MC, for better visibility.
Next up is the DJI "NEZA" GPS module. Common sense would suggest reusing WK-M GPS design and simply swapping firmware / protection / etc between the two would make it cheaper to produce, but I guess with $700 per GPS module-class prices, DJI isn't cutting any manufacturing corners. Naza GPS is a completely different design from WK-M GPS, though still using the same ublox neo6 module and HMC5883L I2C compass. More sawed-off chip tops means the rest of the circuitry is unknown, but it's likely some MCU with CAN, I2C, and a voltage reg or two.
I've ordered the Naza "clone" BumbleBee FC earlier this year when it first came out, as well as Naza around same time. I've taken them apart and took some pics but was too lazy to post them. After making the mistake of not covering WK-M IMU in lead, sidneyw did a much better job with Naza/BumbleBee, and covered everything important in a epoxy-filled lead cube.
Bumblebee is a gimped version of Naza, using what looks like earlier revision of Naza's PCB where they left pads for sensors to be hard-mounted to mainboard instead of connected to external epoxy-filled imu cube. From looking at those, I suspect there's some ST digital gyro, and I already forgot what ACC matched the LGA14 pads (I'm pretty sure it's not ADXL345 though). Pressure sensor is the now-EOL-NRND MS5611-B01 with plastic cap. DJI must really enjoy learning a new processor architecture with each new hardware release, so for Naza/BB they chose to go with NXP's LPC176x series ARM Cortex-M3 MCUs with up to 64K SRAM / 512K flash with ethernet/usb2 host/device, CANbus, running at 100MHz or up to 120MHz with LPC1769.
Nothing interesting here, minor PCB changes for Naza and removal of empty pads for sensors, but still looks like exactly same components as bumblebee.
Boring xray pictures with lead cube covering most interesting parts.
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Last edited by timecop; Jun 21, 2012 at 12:37 AM.
The collapsed posts of TC is due to his forum violations, seems like admins want to punish everybody else, sucks trying to follow threads now, where you cant read easily. I got a slow connection and take ages to unfold everywhere its a collapsed post. I think it's a pretty bad idea with collapsed posts.
I suspect anyone reporting timecop's "violations" would not have lasted 5 minutes in the Usenet forums of old. But, such is life.
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