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[wxsig] Programming/Communicaton Problems

Will Beals will at beals5.com
Thu Mar 23 01:08:48 UTC 2006


Cool on building your own board.  To get the P&E tools working, you need
remarkably little external support.  To get it to work, you need to ensure
that your board is following all of the requirements in Section 15 of the
MC69HC908GP32 Technical data manual.  In there is the schematic of all the
hardware needed which I (mostly) copied in the T238.  The only place I
really strayed from their suggested schematic was replacing the 74HC128 IC
with a single schotkey diode (kind of proud of this myself).  Of particular
note, make sure all the pullup and pulldown resistors on Port A bits 0 and
7, and Port C bits 0, 1, and 3.  I have pullups and pulldowns on there to
get the chip to boot into the right state for P&E tools if the CPUs IRQ line
is pulled high to Vtst (I get Vtst from the MAX232).  Other than that, all
you should need is +5V and the 9.???MHz clock.

Finally, make sure you issue a clean reset to the CPU.  That is harder than
you think.  If you are tying IRQ to VTST, you end up back-powering the CPU
through Vtst.  My solution was to have the RESET button actuall actively
pull VCC to the CPU down through a 10 ohm resistor.

That should really do it.  I'm hoping you missed one of those resistors I
had in the T238 thinking it was for another purpose or something.  If you
are still having trouble, let me know.


-----Original Message-----
From: wxsig-bounces at lists.tapr.org [mailto:wxsig-bounces at lists.tapr.org] On
Behalf Of John Koster
Sent: Monday, March 20, 2006 11:47 PM
To: TAPR Weather Station SIG Mailing List
Subject: Re: [wxsig] Programming/Communicaton Problems

OK, now it makes sense.  You would have been better served to have followed
the classic T238 schematic.  All the pieces would have been in place to
program your MCU from scratch.  That's the platform used to program the
chips we put in the T238+ kits.  

I'm sure Will can chime in here later to give you better advise.  

John, W9DDD

On Tue, 21 Mar 2006, David wrote:

> Hi John,
> I am building the board from scratch, so my PCB layout for the traces 
> are not the same.  However, the general layout of the components are.
> Since I do not have a pre-programmed MCU, I need to program it myself, 
> presumably using the P&E toolset.  I have downloaded the latest 
> software
> (1.15.8) from http://www.beals5.com/wx/ - This is also the same place 
> that I downloaded the manuals, schematics, etc., from.  The bottom of 
> the assembly manual states:  T-238+ Assembly Manual, Rev. 2.1 November 
> 2005, and the operations manual states:  T-238+ Operations Manual, Rev.
> 2 April 2005.
> Software development would be something I'd consider in the future, 
> but for the time being, I'd just like to program the MCU without 
> having to buy a programmer.
> Many thanks,
> David - VA7DMS
> John Koster wrote:
> > Are you trying to do software development, or just load the lastest 
> > revision of the T238 software?
> >
> > Also did you download the correct assembly manual?  Otherwise I 
> > don't understand the comment about the board not being identical?
> >
> >
> >   
> _______________________________________________
> wxsig mailing list
> wxsig at lists.tapr.org
> https://lists.tapr.org/cgi-bin/mailman/listinfo/wxsig

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