Eachine Ex4 / JJRC X12 / C-FLY Faith drone teardown and dissection - Page 1
Forum section: electronics / general

author: muvideo
author_rank: Frequent Contributor
timestamp: October 15, 2020, 08:00:30 pm
content: Hello,while messing around with my drone I made a mistake and fried something inside.So I took the chance to teardown it fully and document it.I'ts a low cost unit (sometimes can be bought around 140€ delivered in eu) with a weightof about 400grams.The name confusion is due to the fact that it is sold under various brands with various names.Despite the low cost it seem decently and cleanly built, has a nice 3 axis stabilized cameraand a dedicated radio control unit. The controller holds and interfaces to owner's smartphonevia wifi and is used for setup and realtime display. The controller also acts as a repeaterfor wifi signal to the drone, it is supposed to control the drone up to 3Km distance.Maybe this is way overestimated and maybe not entirely legal from several points of view...The app for the smartphone is slightly more than a joke, it is working ok but... low low quality piece of sw.Battery is 2.4Ah 3S lithium ion, it's a 4.35V per cell, at 160grams per unit it's pretty energy dense.Still didn't check internal resistance and real capacity.

author: muvideo
author_rank: Frequent Contributor
timestamp: October 15, 2020, 09:40:15 pm
content: Let's remove the top cover, we can see the main board, on top of it there is 3d accelerometer board (with soft rubber mount), 3d compass, Radio unit,4 controllers for spinning the BLDC motors, on the front there is a black pcb that is part of gimbal controlOn the underside of the cover there is the GPS unit, under some aluminium foil tape.Another view with the GPS removed from the underside of the cover anc connected back to main board:Under the main board it's visible the black flat cable that connects the flow camera on the back to the front gimbal unit.Also there is a green pcb on the back that is the ultrasonic rangefinder.

author: muvideo
author_rank: Frequent Contributor
timestamp: October 15, 2020, 10:06:15 pm
content: On the Main board, once removed the compass and accelerometer, can be seen the radio uniton the board there are many useful annotations of the pinoutsOn the underside the MCU is an STM32F412RET6 with 512kB Flash 256kB SRAM, on the fourcorners there are the BLDC motor drivers, in the center there is also a SST25VF010A 1Mbit NOR flah chip.The radio module is an Atheros AR1021X, a wifi dual band unitThe 4 BLDC drivers are built around 4 Fortior FU6831N MCUs, each is driving what seem to be 3 half bridgesmarked "K9 GUC 9V0101" that I was unable to identify

author: muvideo
author_rank: Frequent Contributor
timestamp: October 15, 2020, 10:21:26 pm
content: In order to fly and navigate the drone needs many sensory inputs to understand it's attitudeand location in space. To do so it uses GPS, 3 axis gyroscope, 3 axis magnetometre, and for lowaltitude flights also an ultrasonic rangefinder to measure the distance from ground and a downfacing camera called "flow sensor" that works with the same principle than an optical mouse.I was unable to access the accelerometer used in this board, it is interesting that the boardis ballasted with a mass on the underside, maybe it's needed to reduce it's natural resonance frequency.It is soft mounted on 4 elatic piers.Compass is based on a 3 axis HMC5983 unit:Rangefinder is an ultrasonic unit, it has a HC32F003 micro (never heard before), the board has also aLMV358 opamp, and a SP3232 rs232 transceiver that i suspect is used for driving the transducers

author: muvideo
author_rank: Frequent Contributor
timestamp: October 15, 2020, 10:29:04 pm
content: The gimbal holds and moves around the main camera. It permits to decouple the camerafrom the airframe, to do so it has 3 joints that allow the camera to rotate on the 3 axes of rotation.The function of this device is to compensate for airframe motion in order to have a steady video.It also could roate the camera around, in EX4 the only movement that can be controlled from thepilot is the pitch, the iaw and roll are fixed and aligned to the horizon.For the mechanical actuation every axis contains a BLDC motor, and the camera pcb contains an accelerometerto read actual camera position in space.The top pcb contains the motor drivers3 DRV8313 3 phase bridge driversThis is the back of the main camera pcb

author: muvideo
author_rank: Frequent Contributor
timestamp: October 15, 2020, 10:30:19 pm
content: Main camera (probably the part I fried)The sensor (still don't know the exact pn, should be a 1/3.2" sensor)On the back of the sensor pcb theere is the accelerometer, an MPU-6050

author: muvideo
author_rank: Frequent Contributor
timestamp: October 16, 2020, 06:49:52 pm
content: The main camera video save and broadcast, gimbal control and communication with ground is managed by anothercontrol board, stuffed on the front of the drone:The unit contains what seem an application processor, an intellichip A7, I was unable to find any info about it:On the back ther is the Micro SDCard connector and an unknown ic marked "T25864 PW20R8 EE5185"The only IC i was able to identify is the power management IC RY1303A 5.5V 2AThis board is able also to interface to down facing flow camera

author: muvideo
author_rank: Frequent Contributor
timestamp: October 16, 2020, 07:06:06 pm
content: That's all for now, as soon as I'll have some spare time I'll try to measure battery parameters andalso to understand with what protocol are the motor ESC driven.Someone found that (https://discuss.ardupilot.org/t/c-fly-faith-jjrc-x12-ex4-changing-parameters-and-or-connecting-mission-planner-etc/53245/42)the STM32F412 IC contains a customized version of open source autopilot PX4 firmware,the application processr should contain some linux os.