Denon AVR-3805 RS232-C remote control simply doesn't work

Projects General Guidance
1

I'm trying to control an old denon AVR 3805 via RS232 via arduino (later via an esp8266 via webserver)
Here is the protocol data extracted from the offical pdf: http://www.specsserver.com/CACHE/FILE6615.PDF

Connector type  :  DB-9pin female type, slave straight connection (DCE type) 
( 1pin : GND , 2pin : TxD , 3pin : RxD , 5pin : Common(GND) , 4,6,7,8,9pin : NC ) 
Communication format  : 

Synchronous system: Tone step synchronization 
communication system: A half duplex
Communication speed : 9600bps
Character length : 8 bits 
Parity control : None
Start bit : 1 bit 
Stop bit : 1 bit 
Communication procedure : Non procedural Communication data length : 135 bytes (maximum)

Basically this would be all that I need for it to work on the software side:

Serial.begin(9600);
...
Serial.print("SICD\r");

On the hardware side I've connected a max3232 ttl converter chip. My code itself works. When connecting the arduino max3232 output to an usb rs232 converter, open termite, I see the transmitted text completely fine. When I connect the arduino to the denon, nothing happens.

Fun fact is when using termite, and connecting my computer via the usb rs232 adapter to the denon, everything works fine. (Termite is set to 9600 baud, and transmitting a after text which should correspond to the \r in arduino code).

I also tried to send hex codes via serial.write for all the characters instead of serial.println...the denon doesn't respond to anything...I did a few hours of googling and did not find anything besides that:

https://denon.custhelp.com/app/answers/detail/a_id/83/~/serial-port-response

I tried wiring the signal ground to pin 1 instead of pin 5, cause the pin out description in the official docs linked above seems to have this switched. Still doesn't work

I sadly don't have a oscilloscope to measure the voltage levels that get transmitted between pc and denon.

Any suggestion what could cause this???I already put many many hours into this without finding a possible solution.

Thank you.

2

I'm experiencing the same problem as you, and just found your thread. Wondered if you got yours working? I'm using a Denon x2300, which is newer, but seems to have the same communication specs.

3

After 3 months, you would have a better chance of a reply by sending the member a PM.

4

After 15 months...

No special idea, I'd try \n or \r\n instead of \r.

5

I have an idea that might work. You might be talking to the Demon too quickly. You've got the correct baud rate. When the Arduino transmits serial data, it does so as fast as it can. This can overwhelm the receiving device, especially if it's an older piece of kit.

When you use Termite to send the data, then I'm guessing that each character is sent the moment you type it, which means that there is quite a gap between characters.

On your Arduino, try sending one character at a time with a small delay between characters. You could go big and put half a second between characters to see if it works. If it does, you can reduce the delay until the Demon stops responding and then back it off a bit.

6

9pin connectors are usually less varied than 25pin, but have you tried swapping pin 2 and 3?

7

westfw:
9pin connectors are usually less varied than 25pin, but have you tried swapping pin 2 and 3?

Thank you for the suggestion, this worked!

8

1st law of rs232: it's ALWAYS the cables or connectors being wired "not quite right."

If you're going to be using it a lot, you should buy or make one of these:

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