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Arthur P.

Hacking the I2C interface of Spektrum DX and AR ?

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Thanks Mr. RC-CAM for the fast response

I am sure the Rudder channel is on D3-3 and R4 should be installed, I will check the Ohms just in case..

I hope Brashley can give me further help setting properly the DX7.

You mention to check the correct waveforms on the Rx inputs, how should they look like? I remember testing the output channels from the AR7000 separately and looking at only one signal per channel. Is this what you mean?

Thanks again

Jesse

With everything connected, does your o-scope show correct waveforms on the Rx inputs into the PPM board?

Are you sure you have the rudder channel going to D3-3? Is R4 installed?

I could be wrong, but I believe the heli mode involves special mixing that disrupts the AR7000 channel sequencing; some channels may be sent at the same time. The PPM board would not like that if such a thing occurred.

I don't have a DX7 so I can't help. Brashley would have the details you need.

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When you measure each input to the PPM board, you will see just one servo pulse that is 1-2mS wide that updates every 20mS or so. The pulse width should only change when its assigned stick, and no others, are moved. The update (repetition) rate will remain steady at about 20mS.

The positive going pulse will be about 4V amplitude. Your scope will have no problem sync'ing to this waveform.

Even though they don't show life in the MK tool, have you tried using the information Brashley posted to re-assign the channels to their required positions?

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Thanks MR. RC-Cam for the detail information on the waveform I will check that later since I don't have the board with me.

I will try using Brashley information, I was just worry about hooking up the motors, but I guess I can try them without the propellers.

Thanks

Jesse

When you measure each input to the PPM board, you will see just one servo pulse that is 1-2mS wide that updates every 20mS or so. The pulse width should only change when its assigned stick, and no others, are moved. The update (repetition) rate will remain steady at about 20mS.

The positive going pulse will be about 4V amplitude. Your scope will have no problem sync'ing to this waveform.

Even though they don't show life in the MK tool, have you tried using the information Brashley posted to re-assign the channels to their required positions?

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Mr. RC-CAM,

This is the info I got from each of the channels going to the PPM V3 board, the input voltage was 5v.

Channel: Pulse width, Period, Amplitude

Aux2: 1.8ms, 22ms, 3v

Aux1: 1.5ms, 22ms, 3v

Gear: 1.8ms, 22ms, 3v

Rudd: 1.25ms, 22ms, 3.28v

Elev: 1.4ms, 22ms, 3v

Aile: 1.4ms, 22ms, 3v

Thro: 1.12ms, 22ms, 2.93v

The resistance R4 is right, but I still see signal 7 or the last signal on the series move with Rudd and Throttle. I will try the board the way it is with the MK to see if it works.

Let me know what you think or what other test should I do.

Thanks

Jesse

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You didn't say: do each of the pulse widths change when, and only when, its assigned stick is moved?

Rudder, Elevator, and Ailerons should all be close to 1.5mS when the sticks are centered. The pulse width should travel between ~1.2 and ~1.8mS end to end with the default T-ADJ settings and dual rates switched off (will be more or less if mixes have been altered).

but I still see signal 7 or the last signal on the series move with Rudd and Throttle.

Do you mean you see this in the MK tools, or do you mean it occurs in the o-scope trace?

Does the rudder and throttle inputs to the PPM board look correct? That is, do either move when the wrong stick is moved?

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Mr. RC-CAM,

All these values where observed in the oscilloscope and the travel adjust and Sub trim values where not zero, I had move them, that will explain the different values. I did checked the Throttle and rudder signals and you are right they were separate they only moved with the right input of rudder or throttle so something must be happening on the board then, any ideas? I can try and replace all the components again or do you have any preference in mind?

Thanks

Jesse

You didn't say: do each of the pulse widths change when, and only when, its assigned stick is moved?

Rudder, Elevator, and Ailerons should all be close to 1.5mS when the sticks are centered. The pulse width should travel between ~1.2 and ~1.8mS end to end with the default T-ADJ settings and dual rates switched off (will be more or less if mixes have been altered).

Do you mean you see this in the MK tools, or do you mean it occurs in the o-scope trace?

Does the rudder and throttle inputs to the PPM board look correct? That is, do either move when the wrong stick is moved?

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Can you post an updated o-scope screen shot that shows all the channels on the PPM output? If it is the similar to what I see in the old one (before the resoldering effort a few days ago), then I might have an idea what is going on. Please ensure the Tx is NOT in the heli mode.

Also, are you absolutely sure you have the rudder channel on the correct input to the PPM board? It is the last-channel marker pulse and it must be at the right place or the PPM board will not generate the correct logic.

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Mr. RC-CAM,

Here is what I have done; I took the pictures again of the PPM signal

post-5270-1234383058_thumb.jpg

as well as the signal after the diode array. Still I had the problem of the Rudder and Throttle moving the last pulse.

post-5270-1234383078_thumb.jpg

I clean again the board with methanol etc, and I realized that the D3-3 connector was actually not soldered to the board. I solder back the D3-3 and the PPM signal that I got was the fallowing:

post-5270-1234383107_thumb.jpg

Now I have an extra pulse, my throttle is now moving the seventh pulse and my rudder moves the eight pulse. So I guess is fixed, right ??

Just in case here is the signal after the diode array after fixing the connection of the D3-3 to the board.

post-5270-1234383124_thumb.jpg

Let me know if the pulse signal looks right. By the way is there any reason or problem why my signal is not close to 4 V as you mention before? or why the voltage is different between them?

Thanks for your help Mr. RC-Cam I really appreciate it, I will test it tonight on the MK and let you know how it goes.

Jesse

Can you post an updated o-scope screen shot that shows all the channels on the PPM output? If it is the similar to what I see in the old one (before the resoldering effort a few days ago), then I might have an idea what is going on. Please ensure the Tx is NOT in the heli mode.

Also, are you absolutely sure you have the rudder channel on the correct input to the PPM board? It is the last-channel marker pulse and it must be at the right place or the PPM board will not generate the correct logic.

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You've only got six complete channels there. From what I can tell, your waveform is missing the end of channel separation pulse. This is indirectly provided by the rudder channel, which is the last logical pulse in the PPM pulse train.

To assist in your repair, the signal path is:

R/C Rx rudder channel -> R4 -> U1B -> U2B -> U1C-9.

Also, R2/C2 are involved too.

Again, are you sure that the rudder channel is connected to the correct place on the PPM board? Beyond that, I would suspect a solder connection (open or short) along the signal path described above.

By the way is there any reason or problem why my signal is not close to 4 V as you mention before?

I gave an estimation (I said "about 4V amplitude"). I mostly expected ~3.5V from the Rx, but if you get 3.0V then it is what it is. Keep in mind that I don't have a AR7000 or a MK (never seen either in person) so I am at a disadvantage. All I can do is round up other bits of information I have heard in order to help here. Basically, those of you that have these things in your hands have a huge advantage over little fellows like me. I'm just a pesky back seat driver.

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Very Well Mr. RC-CAM, I will check the path then. However, how does the signal should look like? so I can know when the signal is repaired. The Rudder signal is definitely going to the correct place in the board, but just in case I just attached some pictures of it.

post-5270-1234387552_thumb.jpg

post-5270-1234387562_thumb.jpg

Thanks

Jesse

You've only got six complete channels there. From what I can tell, your waveform is missing the end of channel separation pulse. This is indirectly provided by the rudder channel, which is the last logical pulse in the PPM pulse train.

To assist in your repair, the signal path is:

R/C Rx rudder channel -> R4 -> U1B -> U2B -> U1C-9.

Also, R2/C2 are involved too.

Again, are you sure that the rudder channel is connected to the correct place on the PPM board? Beyond that, I would suspect a solder connection (open or short) along the signal path described above.

I gave an estimation (I said "about 4V amplitude" rather than 4.00V ;) ). Keep in mind that I don't have a AR7000 or a MK (never seen either in person) so I am at a disadvantage. All I can do is round up other bits of information I have heard in order to help here. Basically, those of you that have these things in your hands have a huge advantage over little fellows like me. I'm just a pesky back seat driver.

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Post 139 shows the seven channels (but from the other PPM output).

The rudder channel wiring looks fine to me. But one end of C2 does not look soldered.

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Mr. RC-CAM,

This is the signal that I am getting now, is this not the same as the one on post #139 but from the PPM signal? I am looking at 8 pulses and now the rudder and throttle are separated.

post-5270-1234396007_thumb.jpg

Jesse

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Good, I now see 7 channels. :)

I clean again the board with methanol etc, and I realized that the D3-3 connector was actually not soldered to the board. I solder back the D3-3 and the PPM signal that I got was the fallowing:

Sorry, I didn't notice this comment and I didn't look closely at the revised waveform. That shows it working too, so you already found the problem. Looks like you are done!

Edited by Mr.RC-Cam

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Great.....!!!!!

Thanks for your patience and help Mr. RC-CAM.... I guess I will be able to fly now he he he he

Jesse

Good, I now see 7 channels. :)

Sorry, I didn't notice this comment and I didn't look closely at the revised waveform. That shows it working too, so you already found the problem. Looks like you are done!

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You're welcome. It's my pleasure to help where I can.

Edited by Mr.RC-Cam

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Has anyone in the UK put a V3 board together? I have board and PIC on the way, but am struggling to find the semiconductors in small quantities - maybe someone can point me to where I can obtain these parts easily. Thanks!

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What parts are you short of?

Terry

I can't find the SDM03MT40D diode packs, the 74HCT02 and the 74HCT221 in small quantities - most places are happy to sell me a reel of them!

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Have you tried Farnell and RS for the logic? the diode pack may be harder to find, maybe make it up from single diodes?

Terry

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Have you tried Farnell and RS for the logic? the diode pack may be harder to find, maybe make it up from single diodes?

Terry

Terry - thanks for the help. I'd tried RS and failed, but just found the logic IC's on Farnell, so at least I know I can get them. Those diode arrays are proving problematical though - will have to keep looking!

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I'd just like to proffer a vote of thanks to those on this forum who helped me to get my PPM converter built - the last parts arrived this morning (from Farnell) and I've spent half the day straining my ageing eyes to solder on all those tiny SMD parts to Mr. RC-Cam's board. I fired it up this afternoon and it all worked first time! I'm overjoyed, because, now I can fly my MK on 2.4g! For those that are interested, I'm using Jeti Duplex radio and all channels work as they should. So, a big vote of thanks to Mr. RC-Cam, those who helped me source the parts and those who previously asked questions or provided the answers on this forum. If anyone needs some of the SMD parts for their own converter, please PM me, as I have a few left over.

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Thanks for reporting your success. Another happy 2.4GHz MK pilot. :)

It sure would be grand if a PPM board builder documented their effort and posted some reasonably detailed instructions with a few photos. That would remove some of the mystery from the project. I'll agree all the details are in this multi-page discussion, but something a bit more concise would be very nice.

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