[aprssig] has anyone built/modified a USB to TTL level converter??

Bob k8ys at fuse.net
Fri Jun 3 09:19:46 EDT 2011

well, yeah,

I have an IC706 that it TTL.
I have a MAX233 IC (TTL to RS232 level converter/interface/transceiver)
I have a Sil Labs CP2101 already mounted on a small board with a USB cable,
and I have the drivers for the CP2101. This used to be a "goezinta box" for
a cell phone. 

My goal was to build, kluge together an CI/V that went from USB to TTL by
raiding my junque box.

I have TTL to RS232 level converters that I have built in the past, but I
have never played with USB and since all of my computers these days are USB
and none with a real (semi real) RS232 interface, I brought my question to
this group.


-----Original Message-----
From: aprssig-bounces at tapr.org [mailto:aprssig-bounces at tapr.org] On Behalf
Of Greg D
Sent: Friday, June 03, 2011 2:44 AM
To: TAPR APRS Mailing List
Subject: Re: [aprssig] has anyone built/modified a USB to TTL level

Hi Bob,

Uh, let me see if I have this right...

You are trying to drive your IC706 rig from a computer. The computer has 
a regular (RS-232) serial port (or you can make one with a standard 
dongle), and the radio needs TTL. You want to connect the two, right?

A TTL "high" signal (+3v or so) translates to a negative half dozen 
volts or so on RS-232, and a TTL "low" (0v) maps to a positive half 
dozen volts or so on RS-232. You don't need to make this any more 
complicated than it is.

If you're halfway handy with a soldering iron, to drive the rig from the 
computer, all you need is a transistor, diode, and a resistor or two. 
Let me know if you are interested and I can dig up the schematic. I 
drive my Yaesu FT-736R like this, and it works great.

To drive the computer from the rig, it's something equally simple. The 
Yaesu rig doesn't talk back to the computer (really annoying!), but I 
think the diagram I'm remembering has both directions covered. If you 
can find the schematic for the original FODTrack satellite tracking 
controller, I believe it's in there.

Greg KO6TH

Bob wrote:
> I need TTL.
> I have RS232
> I have USB
> I do not have a RS232 port. Rules out the standard USB to RS232 dongle.
> I think that I want to take an old cell phone to computer interface that
> a USB to RS232 level converter. It is a common chip, and I have the
> I want to take the RS232 from the cell phone cable and feed it to a MAX233
> to get TTL in/out.
> Then use the TTL to talk to the IC706m2g to control the radio.
> Without reinventing the wheel, is there a "better way"?
> Bob K8YS
> _______________________________________________
> aprssig mailing list
> aprssig at tapr.org
> https://www.tapr.org/cgi-bin/mailman/listinfo/aprssig

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