Could you detail exactly how many and where the 100k resistors get installed? Thanks again for the simplicity of this mod.

2. It is not a coincidence, it's OK since 2 pots/switches have been rerouted to the upper ADC's on the Atmega (they were on MOSI/MISO and would have made the communication with the module impossible).[/QUOTE]

I thought that only the Ail and Thr switches were affected (rerouted). Are you saying that the P3 pot is also affected?

Thanks

2 resistors inline with the MOSI / MISO channels that go to the frsky module.

OK, I've checked right now, it's the AIL and THR, so I don't know where your problem could come from.

The 100k resistors worked great....Any other tips please pass along.

Thanks Earl

After setting A1 alarm with the 100k resistors mod. installed I do not get audible alarm (low voltage) via the DHT.

Earl

You're right, I didn't notice this.

I looked on the screen, saw the telemetry data and thought everything is okay. Rssi alarm doesn't work either so it turns out to be okay only from module to 9x and not from 9x to module.

I guess a lower value resistor will solve the issue. I'll investigate when I have time.

A 15ohm resistor will do. It is required only on MISO, you can leave MOSI with no resistor.

I was surprised by how low the resistance should be for the signal to pass. I can't tell the tolerance interval, except that it must be less than 200
Try whatever works and reply back so I can update the video.

edit:

No resistor needed! I've figured out the clicking noise is caused by the interference with the max232 chip, which should be disconnected, as shown below. The image shows the DIY DHT layout of course.

https://45edeaac-a-01847fd9-s-sites....6_IMG_3702.jpg

After you disconnect the chip you won't be able to use the external TXd/RXd of the module, but why would you want that? Since everything can now be programmed from the 9x, the only reason would be to change module firmware using a ftdi interface.
But you would do this first (if you want rom B fw. that enables you to set failsafe from TX) then no more need to do it again.

I have been asked on YT to give some details about the serial communications on the DHT module so here they are.

This is the STM32 datasheet (page 30, second column, pins 30-31 are marked as USART1_TX/RX) http://www.farnell.com/datasheets/1372057.pdf

As I marked in the photo, pins 30-31 are connected (through some traces on another PCB layer, not visible) to pins 11-12 of the MAX323 TTL converter.
Pins 13-14 (converted signal from the MAX chip) are connected to the external TX/RX of the FrSky module (blue marked traces).



So why would someone use a TTL converter to convert the signal back from the external tx/rx (already converted), when it is more straightforward to directly connect to the original tx/rx from the module brain.

Originally Posted by Zen09

So why would someone use a TTL converter to convert the signal back from the external tx/rx (already converted), when it is more straightforward to directly connect to the original tx/rx from the module brain.

lack of understanding on how asych serial interfaces really work. specially true among software engineers but even some experienced hardware designers. there was a time when non-inverted rs232 (idle low) was the rage. ibm pc inherited this polarity from teletypes, minicomputer terminals, etc.. then with the advent of hardware uarts and microcontroller chips 5v inverted (idle high) reared its ugly head and all hell broke loose.

now with incompetent terms like "ttl serial" being tossed around things get even worse. the biggest tragedy is uP designers never quite appreciated the need for polarity control on their uarts (xor gate costing fraction of a cent). so there is huge waste and un-necessary expense on devices like max232.

bottom line: "level" is irrelevant but polarity is critical. few understand this even today.

Hey Guys,

f the connection with the pcb is cut. Would you still be able to use the old turnigy 9x module ?

Cheers

Not sure what you mean.. Why wouldn't you still be able to use the old module?

Originally Posted by RENATOA

I'll try to explain the first two pictures.
His choice was to use the two unused module pins, that in original JR module are used for 6V and former FM antenna, to route the serial line between Frsky module and 9X.
Inside Frsky module these pins are free, I already used them in other project to pass two signals.
In the first picture the thin wires connects these two pins to the Frsky serial line, before the MAX circuit, so to TTL levels, as needed by 9X. This way we have the Frsky serial lines, with good TTL levels available at module pins, and no more external wires / case hole are needed. And also no more need for transistors inside 9X.
But inside 9X these pins are connected to PCB. To make them usable for this purpose, he cut around them in the second picture, making the pads available to transport the serial line from Frsky module inside 9X.

Sorry I'm referring to how emerge cut around the PCB in the second picture. With this done, if i try to use any other tx module i.e old turnigy 9x, wouldn't the cut not make it work?

There are two pins in discussion:
- one is antenna, I mean the older telescopic FM antenna. If you cut this pin, you still can use any 2,4G module, but no an old FM module.
- the other pin is a 6V pin, used by original JR modules only, no other brand adopting this case use it, as far as I know.

Hey guys, I made a blog post where I try to clearly explain what you need to do to your 9X to get it to support the FrSky telemetry: http://www.dgkelectronics.com/how-to...elemetry-data/

Any suggestions what I could add or be more clear about?

Beware, your MOSI connection to 9x seems wrong to me! It is not clear from the picture..

Perhaps you should use my picture http://imageshack.us/photo/my-images/836/detailq.jpg/

And this one for the USBasp interface http://th9x.googlecode.com/svn/wiki/....png?width=600