[KeithRB]

Does anyone have the schematic that Phoenix says is available for the serial adapter for PC programming? I just want to make sure I have the levels right to make sure I can use one of these:

SparkFun USB to Serial Breakout - FT232RL - BOB-12731 - SparkFun Electronics

This is the SparkFun USB to Serial Breakout for the FT232RL, a small board with a built in USB to serial UART interface. This little breakout is built aro

www.sparkfun.com

Also, I have trouble believing that they only have one way communication, So I want to see if they have some multiplexing going on.

 

[Greg Elmassian]

Does the software read anything back from the decoder? If not, believe the one way communications.
I thought I read it did diagnostics, so that implies it is 2 way comm... also the "programming" jack is a stereo plug, 3 circuits, transmit, receive, ground...

Are you just wanting a USV <> DB9 serial conversion? if so, I'd buy a cable for that, they are cheap enough...

greg

 

[Dan Pierce]

Phoenix does read back from the sound units I have and even tells you the model number and you can store your changes and load these changes into another Phoenix sound unit.

 

[KeithRB]

As the attached diagram shows, there is only one signal port, the other two are 5 V and ground, I am pretty sure it is 5 V and not another signal, since it is also used as a VCC for the P5T expansion board. Anyway, the only reason I bring up the serial port is that the Phoenix Sounds website says about the Soundboard to Serial Converter:
"We will happily provide you with a schematic and parts list if you desire, but many components are surface mount and available only from electronics supply houses. This is not a project for the casual hobbyist."

Since I have been an electrical engineer for 30 years or so, I am not afraid. However, since it appears that it does do some multiplexing I would like to see the schematic. I don't know if they provide the schematic for the USB version.
I tried emailing Phoenix Sound, but have not heard back, much like another poster on this board recently reported.

 

[Greg Elmassian]

So, it may be "technically" serial data, but clearly not the RS-232 standard that most people would expect.

Can you share the schematic when you get it? Must be a bidirectional communication line, or use positive transitions for xmit and negative for receive or something like that.

Greg

 

[KeithRB]

I am guessing that the default state is for the PC to listen to the sound card and they just have a tristate buffer that is activated when they transmit from the PC. Since they control the communication, they can just tell the sound card to send data, and how much, so they can prevent collisions.

 

[KeithRB]

Oh, and I am sure that the cable converted the signals to and from RS232, and now USB.

 

[KeithRB]

I got the schematic from Phoenix. I hesitate to post it because of copyright, but I can describe it well enough.

They did send the USB interface schematic. It uses a standard FTDI USB chip - they use the FT230XS. They set it up for 3.3 V logic.

They do connect the RXD and TXD, but instead of a two tri-state buffers, they use a single open-drain buffer on the TXD, a SN74LVC1G07DBVR with a 20K pulldown connected to 3.3 V. They also use a "pre-biased" transistor a MUN2211T1, on the 5 V line from the sound card with a 20K pulldown connected to *CTS.

The only other gothcha is that they use the FTDI setup utility FT_Prog.exe to invert the *DSR signal.

 

[Greg Elmassian]

hah! a little trick to keep people from using a stock setup.

Will you mail the usb schematic to me? clearly there is no charge for it. thanks greg @ elmassian dot com

 

[KeithRB]

Done

 

[Greg Elmassian]

Thank you, received!

 

[KeithRB]

Sorry for the out of focus picture, but here is what I ended up with. The small board is the USB to digital converter and the large one holds the buffer and the transistor switch.

Once I turned the power on to the sound card(!) and lowered the latency (both described clearly in the manual) it all worked great.

 

[Greg Elmassian]

Which manual describes reducing latency?

Thanks, Greg

 

[KeithRB]

http://www.phoenixsound.com/pdf/CDmanual.pdf

This is the standard manual, not the "advanced" one.