[chirp_devel] VX2r

[Andrew Errington]

On Sun, 12 Feb 2012 15:41:17 Richard Farina wrote:
> On 02/12/12 00:34, Andrew Errington wrote:
> > On Sun, 12 Feb 2012 11:28:00 Dan Smith wrote:
> >>> I will try another 4-pin cable.  And I will try a diode between Tx and
> >>> Rx.  It seems to me that the radio is trying to pull down the data
> >>> line, but the PC Tx line is pulling up (idle).
> >>
> >> None of the radios I've built cables for (which is many) have ever had a
> >> diode in the mix. The radio expects to see its own echo, so if you try
> >> to prevent that with the diode, then it will stop transferring
> >> immediately. If you put the diode the other way, then you haven't
> >> changed the circuit any.
> >
> > I'm still not sure.  The radio will always see its own data, as Tx and Rx
> > are connected internally.  If I use a diode then it stops the idle state
> > of PC Tx fighting (pulling up) if the radio wants to pull it down.
> >
> > I have added a diode and I have made some progress.  VX2 Commander 'sees'
> > the radio, but only gets one block of data.  It seems the protocol is
> > block oriented- radio sends some data and waits for something before
> > proceeding.
> >
> > Here's the dump from VX2 Commander:
> > Data Received. Length: 11   Data: 41 48 30 31 35 24 E8 01 00 24 00
> > First Block: [41 48 30 31 35 24 E8 01 00 24]
> > -------------------------------------
> > CPU: 01 00 USA
> > Mod Setting: E8 (Freeband)
> > -------------------------------------
> > Sent: 06 Acknowledge...
> >
> > Then the radio times out and displays "ERROR".
>
> If data is only flowing from the radio now maybe that diode wasn't such
> a great idea?  Pretty sure Dan might have mentioned that....
>
> -Rick WZ3RO

Without the diode I was getting nothing, and there is a good reason to fit 
one.

Has anyone else here used an FTDI FT232R chip to drive a VX2r (or any radio 
with a single I/O for Tx and Rx data)?  Documentation on the web is sparse, 
and mostly concerns circuits which interface directly to RS232-level signals.  
I am also aware of Alexander Meier's design which uses this chip and two 
inverting transistor buffers on Tx and Rx.

I could *buy* a USB interface cable, but that won't teach me anything (the 
corollary being that building my own will teach me to buy one...).

I guess the next step is to try a 5V level output, but as I have said before, 
the internals of the VX2r all run at 3V so it worries me a little.

So, in summary, FTDI FT232R chip running with VCCIO at 3V3:

With TxD tied to RxD and to the radio DATA pin.
With the radio unplugged the VX2 commander loopback test works.
With the radio plugged in, no clone data is received from the radio.

With TxD connected to RxD through a diode and to the radio DATA pin.
With the radio unplugged the VX2 commander loopback test works.
With the radio plugged in, the first block of clone data is received from the 
radio with chirp or VX2 Commander, but no data can be sent to the radio.

73,

Andrew
ZL3AME