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MiniSport Laptop Hacker 09
MiniSport Laptop Hacker - Vol 9 6 Mar 1993
>>> POOR MAN'S PACKET (PMP) ON THE MINISPORT.
Here's the schematic for the Poor Man's Packet on the Zenith ZL1 or ZL2
MiniSport Notebook computers. The notations on this schematic are styled
after schematics provided by VE3SYB or VE3RJO (the reference wasn't clear)
in WB9BBC's PMP Newsletter Volume 2 Number 5.
RX CARRIER
BIAS DETECT
+5v 1 o-----------------------+-----+-----+
/ | /
\<-+ | +->\ 2x100K TRIM-POTS
/ | | | /
# | | | #
| | |
-------------
| 7 1 10 | XTAL
CTS 14 o----------------------|8 16|---+---|(--+
| | === 33pf |
DTR 13 o----------------------|14 15|---+---|(--+
| TCM | #
DSR 16 o----------------------|3 4|----|(----------+--+--+--o RX
| 3105 | .47 | | |
GND 8&4 o--+ +--/\/\/\-----|2 | 2x1N914 /\ /\ /
| | 18k | | | | \ 33
# | +5v +--|5 11|----|(--/\/\/+ | | /
| o | | 9 12 13 | .1 39K | +--+--+
| | | ------------- | #
| \ | | | | |
| 10k / | +--+--+ /
| \ | # 20K \<---|(-----o TX
| / | / .1
| C +---+ #
| | +-----o PTT
| / |
| B |/ |
+---| 2N3904 / C
|\ 4K7 B |/
\ E -----/\/\/---+---| 2N3904
| / | |\
# / / \ E
/ 22K \ |
RTS 15 o-------------------------------- / #
#
CONNECTION = o or + /
/ |/
RESISTORS = /\/\/ or \ TRANSISTORS = --| B, E and C are marked
/ |\
CAPACITORS = |( or = \
DIODES = /\ or \/ GROUND = #
Other PMP schematics show how you can hook LED monitors onto pin 3 of the
3105 (a Packet DCD indicator), and the PTT line (transmit light). The PTT
line goes into my Kenwood TH21AT, which requires no pullup resistor on the
collector of the transistor. YOUR RADIO MAY REQUIRE A PULLUP OR MAY RE-
QUIRE PTT TO PULL THE DC LEVEL OF THE TX LINE. See other PMP documentation
for these complications.
I used 1Mohm pots instead of the two 100k pots. These two must be 10 or 15
turn precision. The 39kohm resistor added in line with the TX audio is
shown on no other schematics I've seen; I needed it to cut the audio down
so that the 20kohm pot could be run about mid-range with my Kenwood TH21AT.
I used some old junky GE-10 transistors. These worked fine except on the
PTT line. I substituted in a 2N2222 on the PTT line.
Using this hardware, some changes to the "PMP.CFG" file have to be made to
direct software to the ZL2 COM2 port. In a nutshell, we need to aim PMP at
the 8250-compatible registers and bits I spoke about in the last newslet-
ter. Look at the previous two issues and compare to these necessary lines
in PMP.CFG:
pttport 0x2fc 2 0
txport 0x2fc 1
cdport 0x2fe 0x20 0
rxport 0x2fe 0x10
No "init" lines are necessary because of the availability of *real* power
on the MiniSport COM2 header (see last issue of MLH).
73, Brian, ka9snf@wb7nnf.#spokn.wa or Internet ka9snf@jupiter.spk.wa
