- Posts: 10
WLToys Q303
14 Dec 2016 14:54 - 15 Dec 2016 02:48 #56818
by ajtank
Replied by ajtank on topic WLToys Q303
One may purchase genuine chips according to the information listed on the manufacturer
website
or purchase a known good module
here
and swap the chip. I got mine from Arrow USA.
Goebish can you tell where you purchased the chips for your module ?
To replace the chip and capacitor one needs to get rid of the screening can first. I use solder wick to remove all the solder at the 4 joints. Then lifting the can up is just a piece of cake. There are a lot of videos on Youtube about the soldering of a QFN, e.g. here. The capacitors are located on the adjacent sides of the crystal, see below in red rectangles:
Goebish can you tell where you purchased the chips for your module ?
To replace the chip and capacitor one needs to get rid of the screening can first. I use solder wick to remove all the solder at the 4 joints. Then lifting the can up is just a piece of cake. There are a lot of videos on Youtube about the soldering of a QFN, e.g. here. The capacitors are located on the adjacent sides of the crystal, see below in red rectangles:
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15 Dec 2016 10:53 #56835
by goebish
Replied by goebish on topic WLToys Q303
I just received your FC, thank you very much for already having soldered leads to the RF board, I only have to connect it to my analyzer 
Now I'll try to understand the tx id / rf channels algo, or at least generate enough to avoid interferences if many people fly Q303 with Devo transmitters at the same time (unlikely, but still
)
Now I'll try to understand the tx id / rf channels algo, or at least generate enough to avoid interferences if many people fly Q303 with Devo transmitters at the same time (unlikely, but still
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15 Dec 2016 12:58 #56842
by brylant
Replied by brylant on topic WLToys Q303
@goebish: do you have any legit spare chips...? I'd take two off you 
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15 Dec 2016 15:11 - 15 Dec 2016 15:11 #56844
by goebish
Replied by goebish on topic WLToys Q303
Work in progress for the Q303 ... that's a real pleasure to crack a protocol when we can tap onto the RX to retrieve expected frequencies with crafted transmitter IDs
I still have to check a few stuffs but the algo seems really simple.
I still have to check a few stuffs but the algo seems really simple.
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15 Dec 2016 15:30 - 18 Dec 2016 03:53 #56845
by goebish
Replied by goebish on topic WLToys Q303
So, it's extremely simple ...
TX id is 32 bit long (arbitrary), but only 2 bits are used to generate the frequencies sequence (4 hops), yes, there are only 4 possible sequences ...
and to answer your previous question, the lower frequency it can use is 2470 MHz and the higher one is 2479 MHz.
I suppose the CX35 is using a similar pattern but with a different base frequency (0x46 here), we'll have to check that
edit: if this theory is verified, the cx35 is using 0x14 as base channel and channels are spaced 3 MHz apart instead of 2MHz on the Q303, ie:That matches with what you captured from the CX35 transmitter:
ID: 24 37 46 89 (offset = 0x24 & 3 = 0)
RF: 14 17 1A 1D
TX id is 32 bit long (arbitrary), but only 2 bits are used to generate the frequencies sequence (4 hops), yes, there are only 4 possible sequences ...
u32 txid = 0xb8696467; // any arbitrary value
u8 freq[4];
u8 offset = (txid >> 24) & 3;
for(u8 ch=0; ch<4; ch++)
freq[ch] = 0x46 + ch*2 + offset;and to answer your previous question, the lower frequency it can use is 2470 MHz and the higher one is 2479 MHz.
I suppose the CX35 is using a similar pattern but with a different base frequency (0x46 here), we'll have to check that
edit: if this theory is verified, the cx35 is using 0x14 as base channel and channels are spaced 3 MHz apart instead of 2MHz on the Q303, ie:
freq[ch] = 0x14 + ch*3 + offset;ID: 24 37 46 89 (offset = 0x24 & 3 = 0)
RF: 14 17 1A 1D
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15 Dec 2016 16:06 - 15 Dec 2016 16:13 #56848
by ajtank
Replied by ajtank on topic WLToys Q303
Great !! The everlasting exploration is coming to an end
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16 Dec 2016 14:03 - 16 Dec 2016 14:06 #56885
by goebish
Replied by goebish on topic WLToys Q303
Next is the CX35, if my theory is right, that's 2 birds with 1 stone
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