[Klug-general] TTL to RS-232 advice

[jwmartnet .]

On 5 January 2015 at 00:11, Brian Reay <brian.reay at gmail.com> wrote:
> What are you trying to do?
>

View TTL serial console of QNAP device on Linux PC.

> In particular, does the device you wish to connect to (not the PC, the other
> 'end') have RS232 or TTL levels? If it is TTL and just Tx and Rx data ( plus
> ground) then a USB device like I mentioned should be fine.

Yes TTL, with TX & RX, plus a green VCC cable. I found another page
for achieving similar with freeBSD, saying to look for FT232 based
chips for USB connectors.

Some of them say 3.3v & 5v. Is the 5v the USB side, and the 3.3v the
TTL side? Or some mention a switch - is that to switch between 3.3v or
5v?

Are the cheap items shipped from China risky? (Hi-powered bicycle
lights from China have a bad rep for exploding batteries,
over-charging, etc).
£2 from China or £10 from UK.

Then am I right to guess the items listed for the Arduino might be a
good choice? Quality, reliable UK based distributor, etc.

> It will appear as
> a serial device under Linux just like any other serial port. All the ones
> I've used, Ubuntu has had the drivers  already installed.

Thanks for your help.
James.

>
> Brian
>
>
> On Sunday, 4 January 2015, jwmartnet . <jwm.art.net at gmail.com> wrote:
>>
>> Thanks for your replies, but I'm clueless about electronics (and
>> evidence seems to be stacking up against me in related areas too).
>>
>> The USB things look preferable, and avoid the need to get a serial
>> cable (and enable the serial port in pc bios) ... I just don't know
>> what the right thing to get would be. The product description in the
>> second of those ebay listing you gave, Brian, doesn't fill me with
>> confidence!
>>
>> Thanks.
>>
>>
>>
>>
>> On 3 January 2015 at 16:53, Brian Reay <brian.reay at gmail.com> wrote:
>> > They are bidirectional in that that the inputs RS232 "side" are convert
>> > to
>> > 3.3V TTL and the inputs on the 3.3V TTL side.
>> >
>> > You mentioned USB, you can buy Serial USB ports of Ebay (and Amazon)
>> > which
>> > have a TTL level output. They are a simple serial interface, ie little
>> > if
>> > any data control signals.  'Flying lead' ends.
>> >
>> > I've used ones like both of these:
>> >
>> >
>> > http://www.ebay.co.uk/itm/F04879-PL2303HX-USB-Transfer-to-TTL-RS232-Serial-Port-Adapter-Cable-Module-/141130969609?pt=UK_Replacement_Parts_Tools_Repair_Kits&hash=item20dc0fb209
>> >
>> > OR
>> >
>> >
>> > http://www.ebay.co.uk/itm/New-USB-2-0-to-TTL-UART-5pin-Serial-Converter-Module-5pin-cables-CP2102-STC-/400644576263?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item5d48471407
>> >
>> >
>> >
>> > Brian
>> > www.g8osn.net
>> >
>> >
>> >
>> > On 03/01/15 16:35, jwmartnet . wrote:
>> >
>> > Hi,
>> >
>> > I want to connect a serial console to my device but need a bit of advice
>> > before purchasing components.
>> >
>> > According to the article linked below, I need a ' 3.3V TTL to RS-232
>> > level
>> > shifter'
>> >
>> > http://www.cyrius.com/debian/kirkwood/qnap/ts-219/serial/
>> >
>> > Do these converters work bidirectional? Or does it specifically need to
>> > be
>> > 3.3V TTL to RS-232 and not RS232 to 3.3v TTL?
>> >
>> > Anything to avoid?
>> >
>> > Probably wishful thinking, but.. I guess TTL to USB wouldn't work
>> > without
>> > intervening electronics?
>> >
>> > Cheers
>> > James