[aprssig] [OT] Some interesting Display Developments with K107

[Brian Riley]

Its been a while and I have been busy on the bench the last few days.  
Since there are dozens of people on both these lists who have  
purchased my K207 serial LCD controller I am posting these two notes;

(1) I found a nice display at All Electronics <http:// 
www.allelectronics.com>. Their part number is LCD-105. It is a non- 
backlit 2 line by 40 character display made by Goldentech. The data  
sheet is a little unclear, but it turns out it is HD44780 compatible  
and therefore compatible with the Anderson chips in the K107. The  
connection is a ribbon and one end is anchored to the display. To  
connect to the K107 you install a 2x7 pin header and the bottom side  
(solder side) of the K107. The Anderson #117 chip is cognizant of the  
2x40 geometry so that is no problem.

(2) I started mucking withe PICAXE chips and the rule of thumb is  
generally that you are stuck with 2400 baud serial. But I found that  
you can put the display onto the programming out port (P0) and use   
the "SerTxd" command which normally outputs at 4800 baud. However use  
of the command "Setfreq M8" to up the internal clock to 8 MHz then  
that baudrate jumps to 9600 baud and you are set! ... well ...  
almost! The "SerTxd" driver is made to talk with a PC. Sooooooo ...  
you need to set the input type jumper to RS232/INVerted. I did this  
with a PICAXE 08M, but should work with any PICAXE supporting "SetFreq."

You must consider with regard to the PICAXE and the Anderson PIC #117  
each operating on the internal oscillators which are subject to  
thermal drift. IF, they both drift, and in OPPOSITE directions they  
COULD begin to show framing errors while trying to talk to each  
other. It was this reason the Peter Anderson created the #108/#118  
chips using a 4 Mhz resonator which is far less prone to drift and is  
almost guaranteed not to drift beyond the PICAXE. So its on a chip by  
chip basis, but definitely worth checking out.

There is discussion, pix, and some sample code for both these issues  
on the K107 section of my Tech Blog ... see the link below.

---
cheers ... 73 de brian  riley,  n1bq , underhill center, vermont
   <http://web.mac.com/brianbr/>  Tech Blog
   <http://www.wulfden.org/DiskShop.shtml>
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