Gruvin9x and FrSky DIY osd. RS232 wiring

[Jim McKeown]

Hi Byran

I would like to review the RS232 wiring requirements before the smoke starts.

I have TGY 9x converted to ER9X with the Frsky 2 way DHT DIY with osd RX.  The DHT board does not seem to have provision for RXd and TXd connection that I can see, unless I wire onto the back of the 4 pin plug.  Or for that matter provision for RS232.  I have the FySky usb cable and programmer and a receiver upgrade lite that is required to change the FW.  I recently purchased a sparkfun  rs232 pcb.  Oh! I have a few more receiver upgrade lites on my bench.

I did installation according to the information given in the article ``gruvin9x Turnigy/iMax/Eurgle/FlySky 9X RC Radio Firmware (forked from ER9X Oct. 2010) plus an enhanced Controller Board design``  I`m caught  up at the TLL txd rxd step.  You`ll recall the diagram you presented doesn`t have a photograph. The diagram was taken from the design for the new mother board.

The information does not show where the TLL connects to the FS DHT (2 way) pcb. I can see where txd and rxd, ground a 5 volts are pinned out of the board but I take it they are for the monitor. 

In the above I`m not familiar with this picture.  The cable marked usbo is part of the FW programming?  The sliver tube is the end of an antenna on a different board.   At the end of the day I would like some directions on the TLL connections inside the TX.  I have a sense that we are dealing apples and oranges.  Rs232 (FrSky receiver upgrade lite) is for FW upgrading, and the Sparkfun pcb board is to communicate with the RX.  Having damaged a couple of boards getting to this point I`m going ask before I make the next move.  About all I remember is not to match rx to rx.  Thank you for your support. 

 

[Bryan]

Hi Jim

Thanks for laying out all the information, as you've seen it -- though it rather looks like a big confusing mess to me.

[rant mode ON]
I'm guessing that you have trying to cobble together information from forum posts. YUCK!! Throw it all away! Seriously. It's not that any of it is necessarily "wrong" ... but it's clearly confusing and disparate, at best. I would recommend that you never consult forums for this kind of information, unless it's the very last resort. (I cannot begin to guess why the (V)HF antenna was left in-circuit in the last photos. What on Earth?! That's just plain BAD news -- begging for an ESD damage event. Sheesh. Anyway ...)
[rant mode OFF]

That said, I can offer is this: http://code.google.com/p/gruvin9x/wiki/FrskyInterfacing, which should be more than enough -- with the exception that a 5V TTL to RS-232 level shifter (say from Sparkfun) could be used in place of the transistor circuit.

I have a sense that we are dealing apples and oranges.  Rs232 (FrSky receiver upgrade lite) is for FW upgrading, and the Sparkfun pcb board is to communicate with the RX.

Yup. Apples sand oranges -- and I think I saw some pears in there, too.

As far as I know, the Fr-Sky part is intended only for programming new firmware into the DHT.  In that regard, it will almost certainly be 3.3V TTL, not 5V, so of no use to you in this application. (Had it been 5V based, you probably could have used it.)

Having damaged a couple of boards getting to this point I'm going ask before I make the next move. 

Fair enough!
 

About all I remember is not to match rx to rx.

Well, someone might have said that somewhere, in the context of doing damage, I guess. But it was not I (I hope.) The main thing is not to connect RS232 (potentially +/- 12V) to the TTL side of things.

It might be more of an issue with chip-based level converter on the TTL side. But in practice, I very highly doubt that would do any harm, since TTL is usually tolerant of such things -- over the short term anyway.

Of course, you won't get any data through if you get it wrong. If everything seems wired correctly after a triple-check and you're not getting data, then try reversing them. You should be fine.

In any case, far as I know, Rx on the '9X (as drawn in green in my schematic) goes to Tx on the DHT. (I've only ever used the DJT module, where that is definitely the case.)

Hmmm. Do note however that the following is somewhat misleading. (I've just realised!) ...



"Fr-Sky" there does NOT mean "connect directly to the Fr-Sky circuitry. You MUST go through a level shifter, such as the two-transistor circuit shown, as explained in the text. I best amend the image.

Thank you for your support.

You're welcome.

Let's now please (in this particular discussion) forget all the 'random' forum post stuff and concentrate on the related gruvin9x Wiki page, so as to give me the opportunity to add to (or correct) that single-source point of reference. In my mind, it has everything you need to know already. But I'm sure to be wrong on that count. This will give me a chance to make a meaningful mends, if needed. Thanks.

--
Bryan.

[Bryan]

I've just updated the two images at http://code.google.com/p/gruvin9x/wiki/FrskyInterfacing. They now look like this ...


... and ...


Hopefully these changes will reduce any future confusion.

Please refer to the Wiki page text for further details.

Bryan.

[Bryan]

Oh and ... as noted on the the Wiki page -- if you use something like the Sparkfun, chip-based level shifter, instead of the transistor circuit, then you will almost certainly have to disconnect it from the circuit every time you want to re-flash the '9X. That would be a right, royal pain.

Can anyone actually confirm this? My thinking is that the forced TTL-low (at rest) output of such chips will prevent the ISP programmer from accessing the ATmega MCU.

Bryan.

[Bryan]

Or is it forced-High? Yes, I think high. TTL serial is inverted, right? Too tired. :/

Either way, some problem.

[Jim McKeown]

Hi Bryan;

I came across something that shows the rs232 connection done directly to the DHT without going through a level shifter.  See http://www.youtube.com/watch?feature=player_detailpage&list=ULMOiKSfD8f6c&v=MOiKSfD8f6c  the question I have should the mosi and miso sp! Be connected directly together or crossed connected.  And of course do you think I should follow this method or not.  I you have some questions maybe we should draw the author into our group.  He doesn’t have much more on his web page but notice he has a small pcb with blue wiring going to his lcd backlite. It would be nice to know what is special about it.

[Bryan]

On 17 April 2012 22:03, Jim McKeown <jimmc...@shaw.ca> wrote:

Hi Bryan;

I came across something that shows the rs232 connection done directly to the DHT without going through a level shifter.  See http://www.youtube.com/watch?feature=player_detailpage&list=ULMOiKSfD8f6c&v=MOiKSfD8f6c  the question I have should the mosi and miso sp! Be connected directly together or crossed connected.  And of course do you think I should follow this method or not.

Well you don't know which one is which from his video anyway, do you? So not posisble to known which way to connect them, other than trial and error, so far as I can tell.

Feel free to do it that way if you like. I hope the DHT module's MCU is 5V tolerant on the its TTL-RX input is all. (There's a good chance it is. But I can't personally say, without scouring data sheets. Just trust the guy in the video, I suppose? Anyone else?)

I'm also not sure how the method can work on the DHT Rx side of things, if the on-board RS-232 level shifter is 'hard' TTL. I suppose if they're also just using open collector or simple transistor inverters, then there shouldn't be a signal conflict -- between the output of the level Fr-Sky RS-232 shifter and the TTL signal you will be supplying. But without a schematic, I cannot know these things, beyond doing it myself and putting it on a scope. But I don't have a DHT module to play with.

We are also left to assume that the 'USBasp' programmer will work OK while the DHT module is wired in this fashion. Without at least open-collector interfacing on the module itself, it's hard to know if it would (without being unplugged for programmer and then reconnected) -- beyond the assumption that it 'must work because the man in the video didn't say anything about it.' *shrug*
 

  [If] you have some questions maybe we should draw the author into our group.  He doesn’t have much more on his web page

With respect, I really don't personally have time to get into it. By all means go ahead and contact him yourself though.

Things get difficult when you're not doing it the same way we are doing it, yet you are asking us for advice. That said, "Whatever works". :-D

but notice he has a small pcb with blue wiring going to his lcd backlite. It would be nice to know what is special about it.

I'm guessing that little board has the required switching transistor on it, as mentioned some time back. He may or may not have made it himself.

Bryan.

[FROMI]

Hello, here are few pcbs designed for MAX232 and 2 transistors (the
last is very tiny:).


On Apr 17, 1:19 pm, Bryan <gru...@gmail.com> wrote:
> On 17 April 2012 22:03, Jim McKeown <jimmcke...@shaw.ca> wrote:
>
> > Hi Bryan;****

>
> > I came across something that shows the rs232 connection done directly to
> > the DHT without going through a level shifter.  See

> >http://www.youtube.com/watch?feature=player_detailpage&list=ULMOiKSfD...

[Ferenc Roman]

Upssy, forgott the project files (Eagle).

[Bryan]

Well, thanks. But alas, we (or at least I) don't use Eagle because it's not open source (free -- as in freedom of speech) software, is far too expensive for serious hobbyists. (I personally dislike it's UI too. But that's probably just me. :P)

Of course, anyone else who is interested can make use of the files provided. But I won't personally be looking. (Nothing personal.)

Bryan
aka Gruvin

[Ferenc Roman]

Ok, its not totally free but freeware so partially free, till:

• The useable board area is 100 x 80 mm (4 x 3.2 inches).
• Only two signal layers used.
• Non-profit applications or evaluation purposes are followed.

Seems like its enough for hobby purposes. At list for me. Sure, I like freedom too :)

[Bryan]

gruvin9x PCB dimensions = 168 x 55mm, only two layers. Cheapest Eagle license to handle that = Pro = USD$700. (Outrageous!)

KiCAD works just fine (no practical size limitations what-so-ever) and is completely free -- both as in "free beer" and "free speech". There's simply no competition, IMHO. :-D

Come to our side. We have cookies. :-D

[Ferenc Roman]

ok, you are right, but I am about in general.. I dont think, that more then 0.5% of hobby modellers will start TX MB designing, approx 30-40% will do some tiny pcbs, others.... will buy on xxx.com. But its just an opinion... and we know that everybody has but nobody is interested in :). Everybody uses what would prefer..


off
By the way, once we are here, I would like to try your PCB. How much is the shipping to Hungary?
/off

[Bryan]

On 16 May 2012 19:39, Ferenc Roman <fro...@gmail.com> wrote:

ok, you are right,

Well, perhaps I made a strong argument. I'm not sure ;right" is the "right" term. :p
 

but I am about in general.. I dont think, that more then 0.5% of hobby modellers will start TX MB designing, approx 30-40% will do some tiny pcbs, others.... will buy on xxx.com. But its just an opinion... and we know that everybody has but nobody is interested in :). Everybody uses what would prefer..

Hmmm. I guess I made it sound like "Eagle sux and KiCAD rules". Really, my point is that we cannot use Eagle for the G9X project and therefore can (or will) not supply files in other formats. But the main reason for this is that it's an open project, using only open tools.

Obviously, most hobbyists -- well, I would guess -- are not publishing open designs. So in those cases, these point carry no relevance.

Hopefully that clears up the parts I failed to day earlier. :-D
 

off
By the way, once we are here, I would like to try your PCB. How much is the shipping to Hungary?

I think it's about USD$7 -- plus or minus $1.50, from memory. I post them air mail, so they take up to 14 days (10 working days) to arrive. The online store will tell you the final cost.
 

/off

Bryan.