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Re: Micromite RS232 interfacing
On 19/06/2014 1:48 PM, Jasen Betts wrote:
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Dear oh dear! Don't trust this person if you want a design that works!

If you connect TTL device to an RS232 device you will have a logical  
inversion problem.







Re: Micromite RS232 interfacing




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I'm not sure what TTL device you are proposing to connect to an RS232  
device.

I thought you were going to connect a Micromite to an RS232 device, and in  
that case the "inversion" problem may be trivial to solve. At least that is  
according to the creator's Micromite Manual where in the "Low Cost RS-232  
Interface" section it says that COM1 can be opened with a parameter to  
invert the output.






Re: Micromite RS232 interfacing
On 20/06/2014 2:27 PM, Andy Wood wrote:
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I think the OP wants to use the PC to program the Micromite, which  
involves communicating with it before being in a position to tell it to  
invert the output.

Sylvia.


Re: Micromite RS232 interfacing




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Ah, I missed that, but perhaps you are right (assuming that PIC has some  
bootstrap serial programming capability - I wouldn't know as I have not done  
anything with a PIC for over a decade).  


Re: Micromite RS232 interfacing
On 20/06/2014 3:23 PM, Andy Wood wrote:
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It's not a virgin PIC. A third-party supplier pre-programs it to support  
a variant of BASIC.

Sylvia.

Re: Micromite RS232 interfacing
On 20/06/2014 7:23 AM, Andy Wood wrote:
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The Micromite is a pre-programmed PIC32. It has been programmed with a  
Basic interpreter and communicates via a serial interface, so you need a  
PC terminal emulator such as Tera Term. The Micromite uses the TTL logic  
convention for it's console serial interface, so you need to use either  
a USB-TTL adaptor or an RS232-TTL interface (which inverts the voltage)  
to connect it to a PC.







Re: Micromite RS232 interfacing
On 20/06/2014 4:51 PM, Yaputya wrote:
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An ideal thing for a script kiddie.


Re: Micromite RS232 interfacing
On 20/06/2014 11:59 AM, keithr wrote:
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Lay off the booze, it is showing in your nonsense
...


Re: Micromite RS232 interfacing

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You've got a serious head-up-arse problem there mate.

read what I wrote.


--  
umop apisdn



Re: Micromite RS232 interfacing
On 20/06/2014 7:10 AM, Jasen Betts wrote:
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You won't get a Micromite console port talking to a PC's COM port unless  
you invert the voltage.
Fact is, TTL logic ONE is positive, RS232 logic ONE is negative.






Re: Micromite RS232 interfacing
On 20/06/2014 8:21 AM, Yaputya wrote:
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Read the subject............





Re: Micromite RS232 interfacing
wrote:

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Please re-read what I said before getting your knickers in a twist.

Re: Micromite RS232 interfacing
On 19/06/2014 3:27 AM, pedro wrote:
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The VOLTAGE is inverted - a TTL positive is an RS232 negative.



Re: Micromite RS232 interfacing
wrote:

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A TTL positive can mean anything.  The logic of what a device outputs
using TTL levels is determined by the DEVICE, not by a particular
convention.

Re: Micromite RS232 interfacing
On 20/06/2014 4:32 PM, pedro wrote:
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You won't get a Micromite to talk to PC's COM port if don't invert the  
signal.
The convention with serial comms is for a TTL logical ONE to be a  
positive voltage. Read the SUBJECT.




Re: Micromite RS232 interfacing
wrote:

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I quite believe that, having not played with them.

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I did.

But you went all extravagant when you claimed:

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 and that ("always") is simply NOT TRUE.

Re: Micromite RS232 interfacing
On 24/06/2014 3:25 AM, pedro wrote:
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It was true when RS232 comms dominated, although we are getting into ancient history. "Always"  
applied when micros operated at TTL compatible levels but RS232 was the standard I/F.
It was the convention for the TTL logic to be the opposite voltage when RS232 was THE serial I/F.
In my experience, programmers wrote serial communication routines expecting the logical ONE in their  
software to be output as a TTL logical ONE, i.e positive. When you wanted an RS232 I/F you added an  
inverter or a MAX232-style chip.
Put it down as a history lesson.






Re: Micromite RS232 interfacing
On Tue, 24 Jun 2014 14:55:42 +0200, yaputya

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(snip)

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It was the more common practice, but far from "always"

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If the TTL logic were positive then obviously an inverting level shift
to/from RS232's inverted logic.  No argument there.

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I've been there (creating custom interfaces to/from RS232 devices) for
probably a bit over thirty years.  The issue with RS232 as a standard
was that it was cited far more often than followed.

Put it down to learning to be less dogmatic in your claims.

Re: Micromite RS232 interfacing
On 25/06/2014 9:34 AM, pedro wrote:
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Almost always ;)


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