Mjx Bugs 3H

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11 Sep 2018 21:16 #70814 by aszasza
Mjx Bugs 3H was created by aszasza
This topic started on the 25th page of the MJX Bugs 3 topic, but since they are very different, here is the new topic for this bird.

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11 Sep 2018 22:01 #70815 by aszasza
Replied by aszasza on topic Mjx Bugs 3H
Here is the first capture, the bind should be in there somewhere. I made it with DSView 0.9.8 on a mac.

Unfortunately I couldn't use any proper triggering because the thing just keeps talking to the rf module. If someone can tell me what to look for I can try to set up the trigger so it starts capturing after a certain data string or value. The channels are CH0:CSN|CH1:SCK|CH2:MOSI|CH3:IRQ|CH4:TXen|CH5:RXen
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12 Sep 2018 01:19 #70818 by planger
Replied by planger on topic Mjx Bugs 3H
You need to record from the TX power on so we can see the init.
Also you need to do multiple dumps in separate files:
- bind
- aileron center/left/center/right center
- same for elevator, rudder, throttle
- any feature button

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12 Sep 2018 01:48 #70820 by planger
Replied by planger on topic Mjx Bugs 3H

aszasza wrote: Here is the first capture, the bind should be in there somewhere. I made it with DSView 0.9.8 on a mac.

Strangely DSView "SPI protocol" exports only the decoded bytes with an ID incrementing every byte instead of every instructions (every starts of CSN).
I'll need to rewrite my decoder so it just decode the stream instead of looking at the instructions.

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12 Sep 2018 15:44 #70840 by aszasza
Replied by aszasza on topic Mjx Bugs 3H
Don't bother I've just ordered one of those 10 dollar analyzers, that should work with the saleae sw, 24 mhz is plenty here. Until that arrives I'll give sigrok a go, maybe that has better decoders.

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12 Sep 2018 18:23 #70847 by planger
Replied by planger on topic Mjx Bugs 3H
Can you at least give a go at recoding from TX power on with your current setup?

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12 Sep 2018 19:36 #70851 by aszasza
Replied by aszasza on topic Mjx Bugs 3H
I messed up big time. As I was taking the remote apart one the solder tabs of the battery holder touched some random trace on the pcb and the radio don't seem to bind ever since. My suspect is the XN297L Chip itself, because the radio turns on, beeps and behaves like normal, but there is no activity on the IRQ line of the radio module. I think that the mcu is okay in the radio because it is trying to communicate with the module but never gets any reply. Is there any place to buy this chip? or a cheap toy drone that is known to be using the XN297L?

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12 Sep 2018 22:56 #70858 by aszasza
Replied by aszasza on topic Mjx Bugs 3H
This little accident really bugs me(pun intended), so I decided to get a cx-10 from amazon, its around 15 bucks and should arrive on friday. I just hope that it has the right chip. If not, its just gonna be for my girlfriend lol.

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12 Sep 2018 23:53 #70861 by C0ckpitvue 777
Replied by C0ckpitvue 777 on topic Mjx Bugs 3H
The bugs 3 mini shares that chip also according to Goebish,the receiver is on ebay for around 12-15 USD.

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15 Sep 2018 12:26 #70915 by aszasza
Replied by aszasza on topic Mjx Bugs 3H
Thanks! I've ordered one of those as well. The CX-10 uses an all in one chip, they must have optimised the manufacturing costs with that. I've also ordered a CX-10D and an x-lite radio with the mpm module so I should be able to test if the protocol works once its implemented. Now I just need to wait for the stuff to arrive. :)

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15 Sep 2018 23:27 #70922 by planger
Replied by planger on topic Mjx Bugs 3H
Can you still do the TX from power on?
There is a big chance that the radio is not checking three response of the xn297l.

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17 Sep 2018 14:13 #70947 by aszasza
Replied by aszasza on topic Mjx Bugs 3H
I can, yes. I'm working til late every day but I'll try to do it as soon as possible. In the meantime, the CX-10D came and it has an XL297 but not the L version. (both the quad and the tx)Do you think if it will still work? I couldn't find the proper datasheets for them, so I can not compare the registers. Should I try to replace it?

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17 Sep 2018 14:16 #70948 by planger
Replied by planger on topic Mjx Bugs 3H
The "L" version has additional/different config registers...

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17 Sep 2018 15:44 #70950 by aszasza
Replied by aszasza on topic Mjx Bugs 3H
so basically its not gonna work for me.

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17 Sep 2018 16:21 #70951 by planger
Replied by planger on topic Mjx Bugs 3H
Most likely. But I still haven't seen the boot and config...

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17 Sep 2018 18:05 #70958 by aszasza
Replied by aszasza on topic Mjx Bugs 3H
Here are 2 captures, one with the faulty radio module still in place and the other one is without the radio module. I know that dsview is annoying, I'm gonna try to do a capture with saleae as well soon.
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17 Sep 2018 18:27 #70959 by aszasza
Replied by aszasza on topic Mjx Bugs 3H
Okay, I've done a capture with logic as well, here it is. This is with the radio module fitted back.
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17 Sep 2018 19:06 #70960 by aszasza
Replied by aszasza on topic Mjx Bugs 3H
Aaaaand here it is with the XL297 just wired in crudely for testing.
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18 Sep 2018 18:20 #70974 by aszasza
Replied by aszasza on topic Mjx Bugs 3H
Good news, I've managed to fix my TX, and also made some captures. here they are.

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19 Sep 2018 16:31 - 22 Sep 2018 12:20 #70986 by planger
Replied by planger on topic Mjx Bugs 3H
I've started to look at the packet structure for the normal mode. It's different compared to the BUGS3 protocol while having similarities.
AILERON, THROTTLE, ELEVATOR, RUDDER values are 0..500.
packet[0]=checksum=packet[1]^..^packet[23]^0x6D <-same as BUGS3
packet[1..3]=TX ID=0x20,0x28,0xBA
packet[4]=THROTTLE>>1=0x00..0xFA
packet[5]=RUDDER>>1=0x00..0x7D..0xFA
packet[6]=ELEVATOR>>1=0x00..0x7D..0xFA
packet[7]=AILERON>>1=0x00..0x7D..0xFA
packet[8]=0x20|AILERON<<7 <- hard to determine exactly since the stick is moving too fast but most likely
packet[9]=0x20|ELEVATOR<<7 <- hard to determine exactly since the stick is moving too fast but most likely
packet[10]=0x20|RUDDER<<7 <- hard to determine exactly since the stick is moving too fast but most likely
packet[11]=0x4E|THROTTLE<<7 <- hard to determine exactly since the stick is moving too fast but most likely
packet[12]=alternates on each packet between:0x00=first packet on RF channel and 0x40=second packet <-looks like change_channel variable of BUGS3, default value 0x86, 0x04 low/high mode, 0x01 picture
packet[13]=flags 0x80=lights, 0x40=arm/0x20=disarm needs to be looked at again, 0x02 and 0x04 pro to altitude 0x00->0x02->0x06 needs to be looked at again
packet[14]=0x00
packet[15]=0x53 <- unknown
packet[16..23]=0x00

Packets are sent every 6840┬Ás.

Bind: NRF_ADDR=0x6D,0x6A,0x78,0x52,0x43 Hopping=0x11,0x1A,0x23,0x2C,0x35,0x17,0x20,0x29,0x32,0x3B,0x14,0x1D,0x26,0x2F,0x38
Normal: NRF_ADDR=0x25,0xB3,0x25,0x3E,0x73 Hopping=0x13,0x25,0x37,0x1F,0x31,0x17,0x28,0x3A,0x1C,0x2E,0x22,0x33,0x19,0x2B,0x3D

Every 13 packets a packet of 16 bytes is received from the model.
rx_packet[0]=CRC somewhat of a sum of something + RSSI
rx_packet[1]=NRF_ADDR[0]
rx_packet[2]=NRF_ADDR[2]
rx_packet[3]=RSSI?

Pascal
Last edit: 22 Sep 2018 12:20 by planger.

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