One of the links above has those pdf's - posted by lincoln
i want to make this a 'learning experience' - i know i don't have a chance / enough time to make a "commercial grade" interface / at least create hardware that can be easily expanded from what i'll be able to implement - that's if anyone will be interested
i want to make it as an exercise - get something isolated from the computer ground and send some data to my R&S SMS signal generator - it's implementing only a basic listener, so i don't have equipment to check more advanced functionality.
I had a lot of stuff that used GPIB at my old job ... here i have an almost usable Hantek ....
i did not think about the front end code - it would be better to make it work with something that's already implemented.
for now i'm looking at the hardware requirements - getting a design that will support the entire protocol / BOM / pcb .
I intend to use MCP2200 for the USB-UART interface ( with flow control ) - is that chip good ? i've only used FTDI until now
Initial BOM sketch-up:
USB B / micro connector ( i prefer USB-B - seems more rugger + trough hole )
USB protection diodes ( are they really needed ? )
leds for RX/TX
MCP2200 + support components configured for 1Meg baud
Optocouplers on RX / Tx / RTS / CTS ( HCPL-2601.S )
5V rail decoupling + filtering for the power supply
Isolated power supply brick or a simple 1 transistor flyback / royer ( i still need to decide - royer will require 2 center tapped windings + feedback + extra inductor )
-------- isolation --------
5V and 3.3V LDO for the output drivers and mcu
STM32F100RCT6TR mcu + support
SN75160
SN75161
protection diodes to GND and a 5.6V high power zener to clamp the inputs + 10 ohm series resistors ( 1206 pref. )
connector:
http://ro.farnell.com/multicomp/spc15336/connector-centronics-plug-24way/dp/2112386 for the first version - pull it out of the case and install it on the board edge
SWD debug interface
2-4 leds to show status, etc
Layout constraints - 100x50mm - if the connector lands fit in this area, try to have components only on 1 side so it can be assembled on a hot plate
I'll add a schematic as soon as i have one available ( estimated: end of next week )