

Date: Tue, 16 Jan 1996 16:09:15 -0500 (EST)
From: Jan Vicherek <jvichere@undergrad.math.uwaterloo.ca>
Subject: Success with MAX 233 for CASIO (BOSS SF-5500B) computer link.


 Success:

 Part list:

MAX 233 or equivalent (e.g. DS233)
2x 1N4148 diode
78L05 -- "L" is important there -- means low quiescent current !!! 
DB25 or DB 9 female + shell (I managed to squeeze the 20-pin MAX 233 into 
	the DB25 cover)
thin, flexible, light two-wire shielded cable (otherwise it will drag your
organizer off the desk). 
2.5 mm jack
tie-wraps (good to secure the cable against careless handling)
            

I connected the 233 chip as shown on functional diagram on 
 http://www.dalsemi.com/DocControl/DataShts.web/drivers/ds233a.html
(on the 233 chip are connected : 11-15, 16-10, 12-17, 6-9(Gnd)
pin 4 goes to pin 2 of DB-25
    5             3
    2         innermost pin of the jack
    3         middle pin of the jack
)

ground is : pin 6 & 9 of 233 chip, pin 7 of DB-25, middle pin of the 
78L05 and shielding of the cable (
the shielding is connected to the 
outermost pin/plate/contact/cylinder of the jack).

T1in connected to innermost pin of Casio jack, R1out connected to middle 
contact, ground connected to the outer contact.

the cathodes of the diodes go to pin 20 and 4 resp.
the anodes are connected and go to input of the 5V stabilizer.
output of the stabilizer goes to +5V input of the 233 chip (pin 7)


I used the DB-25 (warning: DB-9 has different pinout !)

DB-9 to DB-25 conversion:
1	8
2	3
3	2
4	20
5	7
6	6
7	4
8	5
9	22

    Good Luck !!


/CYA on ;-)
I take no responsibility whatsoever for correctness of the information
provided above. 
/CYA off


      Jan

:r ~/.sig                      http://csclub.uwaterloo.ca/~jvichere
Jan Vicherek               Jan.Vicherek@UWaterloo.Ca, honza@ied.com
ZZ                                "To some, nothing is impossible."
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