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

[Rich Osman]

On 6/2/2011 9:58 AM, 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 has
> a USB to RS232 level converter. It is a common chip, and I have the drivers.
>
> 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
Several folks have already mentioned the modules and cables available on
eBay.

You'll find that the majority of early cell phone USB cables were serial
to TTL or 3.3 V logic levels.  I've never seen one that was actually
RS-232 levels, though I've been told they exist.

Most of these were built with just a few chips, the Silicon Labs CP2102,
TI TUSB3410, PL2303, FTDI and some others. Many (most?) store the VID
and PID in EEPROM and can be restored to use the chipset manufacturers
drivers. Most require access to an IC pin, and the devices are molded on
the connector.  They all have drivers supplied but the IC manufacturer,
but they look for the default VID/PID, but most of the phone specific
drivers look for a specific responses from the phone and won't work as a
simple serial device - even though they are.   I suspect that reverse
engineering these will be more trouble than they are worth.

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Rich Osman;  POB 93167; Southlake, TX 76092 (Near DFW Airport)