QCX CAT on Rev T.05 not working but OK on Rev T.04 #cat #mods #solution


 

The QCX CAT interface using a TTL to RS-232 converter will not run above 9600 bps.

I suspect that the higher speed on Rev T.05 is too fast when using a RS-232 to TTL converter.  Probably just fine with a USB to TTL converter.

The QCX is unable to decode characters at 30,400 bps - I have a 20 foot RS-232 cable which could be causing the problem or perhaps 30,400 is just too fast for the firmware to decode at that speed.

The symptom is the QCX immediately respond with ?; when *any* valid character is inputted using Rev T.05

Took a while to figure this out  ...

--
73, Bernie, VE3FWF


Hans Summers
 

Hi Bernie

I'm surprised the totally different voltage levels of RS232 worked at all... the QCX should definitely always be used with 5V TTL logic serial data. 

T1.05 changed the baud rate to 38400 partly because at 9600 baud if the CAT port was very busy, it just about started to worry me that it could cause marginally noticeable delays on the display update. The QCX has no problem at 38400 baud. 

73 Hans G0UPL

On Fri, May 15, 2020 at 7:35 PM Ham Radio <bernard.murphy@...> wrote:

The QCX CAT interface using a TTL to RS-232 converter will not run above 9600 bps.

I suspect that the higher speed on Rev T.05 is too fast when using a RS-232 to TTL converter.  Probably just fine with a USB to TTL converter.

The QCX is unable to decode characters at 30,400 bps - I have a 20 foot RS-232 cable which could be causing the problem or perhaps 30,400 is just too fast for the firmware to decode at that speed.

The symptom is the QCX immediately respond with ?; when *any* valid character is inputted using Rev T.05

Took a while to figure this out  ...

--
73, Bernie, VE3FWF


 

Hans:


Sorry for the confusion.  I am using a RS-232 to TTL level converter.

The logic  levels are 0 and + 5v into the QCX.

I suspect 30,400 bps is marginal using RS-232 at that  speed with a 20 foot cable. Maybe other folks are having that same problem?.

At 9600 there was no issue using T1.04 with the identical hardware setup.

I will order a USB to TTL converter 
--
73, Bernie, VE3FWF


Lawrence
 

Yes I suspect you are right.

RS-232 uses -v to +v swings in voltage and was nominally spec’d at -15v to +15v but a large number of ‘converters’ do things like use -3.3 to +3.3 or even 0 to +3.3 (or 5v)  and it may be that your ’terminal’ is not working well at higher speeds with the low / odd voltages.  The USB would not care as the serial port is virtual.

73, Lawrence
VA7EDU

On May 15, 2020, at 11:19, Ham Radio <bernard.murphy@...> wrote:

Hans:


Sorry for the confusion.  I am using a RS-232 to TTL level converter.

The logic  levels are 0 and + 5v into the QCX.

I suspect 30,400 bps is marginal using RS-232 at that  speed with a 20 foot cable. Maybe other folks are having that same problem?.

At 9600 there was no issue using T1.04 with the identical hardware setup.

I will order a USB to TTL converter 
--
73, Bernie, VE3FWF



Roger Hill
 


Bernard

You keep mentioning 30,400 for the baud rate. That should be 38,400 I think.

Or was that just a typo?

Roger
G3YTN
On 15 May 2020, at 14:20, Ham Radio <bernard.murphy@...> wrote:

Hans:


Sorry for the confusion.  I am using a RS-232 to TTL level converter.

The logic  levels are 0 and + 5v into the QCX.

I suspect 30,400 bps is marginal using RS-232 at that  speed with a 20 foot cable. Maybe other folks are having that same problem?.

At 9600 there was no issue using T1.04 with the identical hardware setup.

I will order a USB to TTL converter 


 

Sorry wrong speed used - senior’s moment. You are correct.  
--
73, Bernie, VE3FWF


Roger Hill
 

So did that fix your problem?
Roger

On 15 May 2020, at 14:38, Ham Radio <bernard.murphy@...> wrote:

Sorry wrong speed used - senior’s moment. You are correct.  
--
73, Bernie, VE3FWF


 

I will check my RS-232 to TTL converter with a scope to see what the RS-232 levels really are. It uses a MAX232 chip with VCC being 5 volts.
--
73, Bernie, VE3FWF


 

The speed I used was correct.  See comments on this thread regarding RS-232 at higher speeds ...

Working great at 9600 bps with firmware Rev T1.04
--
73, Bernie, VE3FWF