Subject: Re: [E3-hacking] Cheap PL2303 cable @ Ebuyer

From: Matt Evans <[email-masked]>
Date: Thu, 7 Jul 2005 15:35:13 +0100

On 7 Jul 2005, at 15:26, Rahim Nathwani wrote:

> http://www.ebuyer.com/customer/products/index.html?product_uid=51518
>
> It's USB at one end, and Nokia pop-port at the other.  It doesn't play
> nicely with current versions of Nokia PC Suite, but might be a good
> alternative to a home-made MAX232 (which would probably work out 
> around the
> same price).

That looks like a bargain!  Also - the picture's a little small but 
that looks very much like the T610 cable I have, so hopefully same 
manufacturer.  (There's a little rectangular 'pod' with a PCB inside.)  
If it is the same as the one I have then it has the advantage that it's 
not sealed into a resin glob, but there's the disadvantage that it 
needs a mod for 5V which requires soldering a tiny leg on the PL2303.

-Matt

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From: David Given <[email-masked]>
Date: Wed, 13 Jul 2005 12:56:18 +0100

On Thursday 07 July 2005 15:35, Matt Evans wrote:
[...]
> needs a mod for 5V which requires soldering a tiny leg on the PL2303.

Well, I now have one. I should be getting scans of it reasonably soon. The 
phone end of the cable is marked N-5100; oddly, that seems to be the only 
mention of what kind of phone it's for...

The plastic box the PCB is inside has a space for a switch, marked L and R, 
but there is no switch there and there are no pads on the PCB for 
installation of one. I suspect someone's been saving money.

Here's the PL2303 data sheet:

http://tech.prolific.com.tw/visitor/fcabdl.asp?fid=33962507

I can't tell whether my device is set up for 5V or 3.3V; I'll just have to 
plug it in and measure it. Is it known that the E2 *doesn't* work with 3.3V? 
And what's the modification I need to do?

-- 
+- David Given --McQ-+ "`Aplysia californica' is your taxonomic
|  [email-masked]    | nomenclature.
| ([email-masked]) | A slug, by any other name, is still a slug by
+- www.cowlark.com --+ nature." --- drushel on a.f.c

---

From: Matt Evans <[email-masked]>
Date: Wed, 13 Jul 2005 14:07:50 +0100

Howdy David,

> installation of one. I suspect someone's been saving money.

Sounds like mine - box-wise - though the PCB is different.

> And what's the modification I need to do?

Yeah that's probably the best way - see if TxD is 5V or 3.3V.  The real 
issue isn't whether the E2 will talk at 3.3V (IIRC it /does/ work at 
this voltage) but whether you'll zap the input on the PL2303 by driving 
5V into a 3.3V input.

*reads datasheet, which always helps*  OK, no, you should be alright 
:-)  It says the inputs are always 5V-tolerant.  So, it will probably 
Just Work - cross the voltage-too-low bridge if you come to it.  
(Modify the cable to run I/O at 5V rather than 3.3V if necessary.)

Good luck!

-Matt

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From: David Given <[email-masked]>
Date: Wed, 13 Jul 2005 15:56:24 +0100

On Wednesday 13 July 2005 14:07, Matt Evans wrote:
[...]
> (Modify the cable to run I/O at 5V rather than 3.3V if necessary.)

Actually, it never occurred to me that it might be in danger --- the idea of a 
USB slave chipset that can't cope with 5V inputs is a bit bizarre, given that 
USB is all 5V!

(In fact, I'm a little bemused about why the PL2303 is powered off 3.3V.)

Looking closely at the PCB it actually looks like quite a nice little thing; 
there are pads for all the output signals, so if you want DTR or RTS they're 
available, and there's a whole bunch of diagnostic pads of unknown purpose. 
There's also a 8-pin IC blank and a six-pin jumper blank. I suspect this is 
for the PL2303's configuration EEPROM. There's definite hacking possibilities 
here.

-- 
+- David Given --McQ-+ "There are two major products that come out of
|  [email-masked]    | Berkeley: LSD and Unix. We don't believe this to be
| ([email-masked]) | a coincidence." --- Jeremy S. Anderson
+- www.cowlark.com --+

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From: Jasmine Strong <[email-masked]>
Date: Wed, 13 Jul 2005 15:59:08 +0100

> (In fact, I'm a little bemused about why the PL2303 is powered off 

Some phone CPUs have embedded UARTs that are not 5v tolerant.

-J.

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From: David Given <[email-masked]>
Date: Thu, 14 Jul 2005 14:52:36 +0100

On Wednesday 13 July 2005 12:56, David Given wrote:
[...]
> Well, I now have one. I should be getting scans of it reasonably soon.

Scans available:

http://www.cowlark.com/amstrad.html

I'll stick a plug on it this weekend and see if it works.

-- 
+- David Given --McQ-+ "Preacher, don't the Bible have some pretty
|  [email-masked]    | specific things to say about killing?" "Quite
| ([email-masked]) | specific. It is, however, somewhat fuzzier on the
+- www.cowlark.com --+ subject of kneecaps." --- Firefly, _War Stories_

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From: Peter Riocreux <[email-masked]>
Date: Thu, 14 Jul 2005 15:20:37 +0100

>From the pics it looks like it is built to take a 9-pin D connector -
even the mechanical mounting holes are there. That would make it more
versaitile I think - a lead with the appropriate 9-pin D and whatever
connectors can then be used for each relevant project.

That assumes of course that connecting a 9-pin D pulls the things out
on the right pins ....

Pete

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From: Matt Evans <[email-masked]>
Date: Thu, 14 Jul 2005 15:45:43 +0100

> connectors can then be used for each relevant project.

It'd be a little tempting (for those sleepy late-night engineers) to 
plug a real RS232 plug into that DB9 though, which'll probably zap the 
PL2303 ;)

I just looked at the scans - that board is the same as mine - first 
picture, look at the pads along the bottom.  That's where my switch is. 
  I believe there's space for a SMT MAX232-alike on there, and inductors 
- i.e. the board is designed for a full RS232-USB serial dongle.

-Matt

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From: Jasmine Strong <[email-masked]>
Date: Thu, 14 Jul 2005 16:03:37 +0100

> plug a real RS232 plug into that DB9 though, which'll probably zap the 

Use a 9-pin mini-DIN, Macintosh-style, then?

Also Psion Series 3 style and newer Sun style, I recall.

-J.