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Mar 29, 2012, 02:08 PM
Team Wack-a-Mole
Melnic's Avatar
I understand what you are saying but most people reading the thread won't find Idle high and idle low as description of USB to serial dongle that will work. They will see USB and TTL in the title. Know what I mean?
Like here:

Then there are goofballs like this:

note how the board says USB to 232. It's not an RS232 to USB converter, it's USB to serial TTL.

RS232 should be moving between a + and a - voltage on the signal in reference to ground.
TTL should be moving between a + and a 0V voltage in reference to ground. With a minimum threshold for a + above a certain voltage and a minimum threshold below a certain voltage for the low end, but TTL should not go negative in reference to ground. RS232 WILL go negative in reference to ground.
Last edited by Melnic; Mar 29, 2012 at 02:15 PM.
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Mar 29, 2012, 04:14 PM
RC beginner
as i mentioned from the start we do agree that most people use the term ttl. that is the root of the problem. however if you read my last post and your wiki link carefully you may realize that what you think a signal "should" do does not always coincide with what actually happens.

for example an rs232 output WILL NOT go negative in reference to ground if connected to a modern logic input. essentially theres a 2k resistor in series and it WILL get clamped to ground with no harm to the ic. same for vcc. i can go into considerably more detail on the subject of input protection zeners in cmos/bipolar logic and in microcontrollers if you like. its a fascinating subject.

also note that, going in the other direction, modern 1.8v, 3.3v, and 5v logic outputs WILL switch an rs232 input reliably. id suggest reading specs for the lm1488 and lm1489 interface chips i referred to which are still hidden inside lsi devices on motherboards and anything else that has serial.

btw goofball is somewhat justified in calling it rs232 because inverted rs232 is technically still rs232. just not the type we are familiar with on old computers. you might also be interested to learn that most recent db9 normal (non-inverted) rs232/usb dongles output 0-5 instead of the classic +-12.

so to repeat: level dont matter but polarity does. it is a free world though and you are allowed to disagree. its just a shame that popular myths complicate asynch interfacing when in reallity it is quite simple.
Mar 29, 2012, 04:24 PM
Registered User
willy163's Avatar
Hi Dave, Hi Melnic.

In my opinion both of you are right.
Idle high will work if connected to idle high regardless of voltages and idle low will do the same if connected to idle low.
The point is that this kind of information is quite never available in serial electrical descriprtion of a device.
The only available information is TTL voltage level or standard RS-232 voltage level.
Ok, voltage is irrilevant but this information is the only one that allow you to choose the right logic level (idle high or idle low although you don't know what it means) to be quite sure to make device communicating.

Mar 29, 2012, 04:46 PM
Team Wack-a-Mole
Melnic's Avatar
I can definitly agree to dissagree.
I've never tried to get a 0-5V chip to work with RS232. Pretty much always used a max232 or 202 chip when doing RS232 so can run off of 5V only supply cause they have the internal charge pumps. If there are cases where you can get 0-5 logic signals to work with an RS232 chip on the other end, great. Just not going to go against the standard when I do work. Our argument is irrelevant cause what people are going to buy are USB to TTL converters and if you see one that says TTL but has the signal inverted and does not work right, then go ahead and alert the thread.
Peace out....
Mar 29, 2012, 05:22 PM
RC beginner
Originally Posted by Melnic
I've never tried to get a 0-5V chip to work with RS232. Pretty much always used a max232 or 202 chip
that explains a lot. you might try it some day as an experiment and let us know what happens.

Originally Posted by Melnic
if you see one that says TTL but has the signal inverted and does not work right, then go ahead and alert the thread.
actually all "ttl" have the signal inverted. one thing that always bothered me was lack of polarity (inversion) control on virtually all pic and avr micro uarts. being forced to use expensive max chips or even a more common sense transistor or logic inverter. all for want of an xor gate on the die that would cost in the order of 1/100th cent.

it was a huge problem back in the days of non-inverted (idle low) rs232 but not so bad now that the modern pc has no rs232 ports. so 5v inverted usb dongles are far more popular than the db9 true rs232 ones which is good because almost no reason to use a max chip now (not that there ever really was).
Apr 02, 2012, 05:41 PM
Registered User
Originally Posted by Telemachus
I have come up with a way to use an S-video cable as a trainer cable to connect two flysky 6ch radios to help "Train" someone else. Some minimal extra internal wiring and a toggle switch are needed on the Master controller, but any standard S-video cable should work to connect the two radios through the "Trainer" port when the modification is complete. Also, both radios have to be programmed IDENTICALLY (and have the pots working) or this will be of no use. The SLAVE radio gets power through the S-video port from the MASTER, so does not need to be on, and does not transmit anything.

As has been pointed out by others, there is "PMM" (Pre-transmitter) data sent through the trainer port on Pin 1 in the diagram in this post:

The key is taking this PMM data from the SLAVE and sending it directly to the RF module on the MASTER. A switch is added to the MASTER radio that selects between internal PMM data and external PMM data sent through the S-video cable. Since the S-video cable carries 5V and grounds both radios together, the Slave is powered enough to create PMM data when in the off position without trasmitting anything through the antenna.

If the pics don't make it clear, let me know, but I can verify that it works.

This in no way affects the ability of the radios to be programed through this same port. The BUDDY radio can still be used as a full radio, and the Master works as originally as long as you don't hit that trainer switch in flight! However, the MASTER box can not be used as a BUDDY box following this mod. (In order to do so, you would need to use a double throw, double pole switch to set it back to normal when the switch is off.)
Does anybody know if it is possible to use FlySky TH9X transmitter as master and FlySky CT6B as slave (for training purposes).
Apr 02, 2012, 08:19 PM
Team Wack-a-Mole
Melnic's Avatar
Originally Posted by dave1993
heres a pic of correct cp2102 to t6 wiring. if you recall you, angrybirdie, and i had a discussion back in post 4966. it turns out his diagram was wrong because that adapter is not labeled right. he figured this out later but did not bother to fix it so i took the liberty. so be aware that not all usb/serial adapters are labelled correctly which is the case here. rx is actually an output and tx is the input on this one. this is a constant source of trouble for noobs.

drivers are another problem area. there are only 2 types: cp2102 and pl2302. you must use the latest version from each mfg or things just wont work with latest windows. drivers downloaded from 3rd party sites are often outdated and another source of headaches.

also referring to 5v or ttl or 12v is a bad idea even though everybody does it. in fact levels do not matter at all. 12v works w/5v and visa versa. polarity is the real issue and people should use terms like "idel hi" or "idle low" not ttl or voltage which is virtually immaterial.
OK, just for clarity, Pin 3 is an Output or INPUT on the TX?
In otherwords, is Pin 3 the TX's transmit or the TX's recieve?
Apr 03, 2012, 08:15 AM
Registered User
Originally Posted by Melnic
OK, just for clarity, Pin 3 is an Output or INPUT on the TX?
In otherwords, is Pin 3 the TX's transmit or the TX's recieve?
Chassis connector pinning as seen at the back of the transmitter

 		   /	         \		
		 /     [   ]     \		
		|                 |	
		| o 1         2 o |	
		|                 |	
		|  o 4       3 o  |	
		|                 |	
		 \       _ _     /		
		   \ __ !   !__/		
Pin 1  : PMM signal 
Pin 2  : +5 Volt
Pin 3  : RX RS232 Serial data input  ( TTL levels(0..5Volt) , ATTENTION !!! NOT RS232 levels(+15..-15Volt)
Pin 4  : TX RS232 Serial data output ( TTL levels(0..5Volt) , ATTENTION !!! NOT RS232 levels(+15..-15Volt)  
Shield : Ground

What I found

Last edited by ReSt; Apr 03, 2012 at 08:22 AM.
Apr 03, 2012, 08:44 AM
RC beginner
you can always rely on reinhard for reliable and helpful info. i like his ascii diagram a lot because its compatible with more readers and more efficient than the jpg version. just in case you do like pretty colors heres the one keepitsimple posted early in this thread. remember the labels show radios signals not those of connected appliances:

Apr 13, 2012, 07:58 PM
They were made by Schluter
Picked up a $3 USB 2.0 to UART TTL 6PIN Module Serial Converter CP2102 from eBay but was too impatient to wait for the S-video cable so I tried an old keyboard extension cable from which i broke out two unused pins and the key. Soldered it up per the diagram below from Dave1993's post #5082 and can now save a config file or otherwise program the CT6B transmitter. Thanks for your help men!
Name: cp2102.jpg
Views: 255
Size: 137.2 KB
Description: USB 2.0 to UART TTL 6PIN Module Serial Converter CP2102 for CT6 programming cable.
Last edited by HeliStar; Apr 14, 2012 at 03:15 AM.
Apr 13, 2012, 09:58 PM
Team Wack-a-Mole
Melnic's Avatar
Guys, I took one of my SIlabs based T6 cable and cut the line, I needed a USB Virtual serial port to TTL output to test a GPS. I found that only TX,RX and GND were connected. There was no wire for + on it. My GPS was powered by my Quad controller so I just connected up the T6 cable ground tandem with the Quad controller ground, then the Tx/RX to the GPS. Everything worked fine.

Dave, are we connecting 2 different driven +5V power sources together here (usually bad) or do these USB to serial TTL boards NEED the +5v to power them instead of pulling it from the USB? Does the +5V on the din of the T6 even go anywhere?

Found this post, looks like they all go somewhere..
there should be 5 lines, GND, +5V, Tx, Rx, PPM
You can see them going to the white connector. black, red, yellow, orange and white
Last edited by Melnic; Apr 13, 2012 at 10:04 PM.
Apr 14, 2012, 08:14 AM
RC beginner
Originally Posted by Melnic
Dave, are we connecting 2 different driven +5V power sources together here (usually bad) or do these USB to serial TTL boards NEED the +5v to power them instead of pulling it from the USB?
you can power the radio with internal batteries, external dc supply, or both at the same time. ive been using all three methods with my t6 and 9x radios. like with the rs232 stuff there are many popular myths regarding connecting two regulators. in fact, since these devices are incapable of sourcing significant current, there is no harm in paralleling them.

true for esc becs too. a friend of mine who was a professional designer of rc controllers and regulated supplies used to argue endlessly with "armchair experts" in the power system forum. lol! eventually most came to realize the truth but there are still a few who stubbornly refused to accept reality. being educated in regulator design myself im convinced there is never a problem.

i had to laugh at those in the multicopter forum who told me they blew out motors, receivers, escs, and mcu units doing it. who knows what else they had going on (or if they ever really blew anything). if course we all make our own decisions but i never hesitate to parallel similar dc sources. 12v to 5v or 5v to 3v... thats a different story.
Apr 14, 2012, 11:10 PM
Team Wack-a-Mole
Melnic's Avatar
I can see if you have 2 ESCs with 7805's in each one, but are there any ESCs that may run other than 5.0V? I know my Align and Castle ESCs and BECs can run variable voltages. Yea, I"ve run one of my Quads tying all the Power's together cause that's how it came but they are all the same brand/model.
Apr 16, 2012, 06:36 AM
RC beginner
i agree that connecting a 6v bec (which IS a common setting) to a 5v one is not a good idea. in that case one will bear the load but no potential (pun) for harm though. and ive seen 7805s vary by as much as a half volt too. for low current applications it certainly dont hurt to "cut the other red wire". i also have a multicopter (actually now i have 5 due to winning a contest) and the choice was either connect all the becs together or use a ubec. if i chose the latter i would have lost because it was a minimum cost competition and i just got by with $2 less than my only real opponent.

switchers are another subject. theoretically due to the feedback loop you should not parallel them. ive done it with a couple ebay 3a units for running bldc motors on the bench (7a) and it did work but i suspect there may be designs where it might fail.
Apr 24, 2012, 03:23 PM
Registered User

New Programmer for Mobiles Android and Bluetooth

Hey guys

Here is a new version of the programmer for mobile phones with Android OS and Bluetooth Wireless Transceiver Module RS232/TTL. Finished version will be ready hopefully within a month.
Many days of work.
Using the programmer can perform:
  • Make changes to all parameters
  • Keep any number of settings (models) of their name
  • Retrieve the current settings from radio
  • ! Import settings from an XML file from the program DigitalRadio!
  • Export all settings to an XML file compliant with DigitalRadio
  • Save the settings selected in the transmitter (not demo)
  • Modify settings offline

Some of screens shot

Good luck in testing.

www (

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