Vermes
Advanced Member level 4
The system has RS-232 outputs in TTL and V.24 versions with all signals, what means DCD, RX, TX, DTR, DSR, RTS, CTS, RI.
FT232RL system provides signal conversion USB-RS232 TTL.
MAX235 system from MAXIMA samples is used as converter of TTL to V.24 signal levels. MAX485 system is responsible for conversion of RS232 TTL to RS-485. A differential resistor (terminator) 120ohm is on the output. It is attached by a jumper. It is possible to control the direction of transmission with FT232 by setting TXDEN bit.
MAX235 system was chosen because it has in-built condensers and doesn't need external elements. Also, it has 5 transmitters and 5 receivers. As a replacement, MAX205 system can be used. To secure the receivers' output lines against short circuit (very low current) when using the TTL output, 10k ohm resistors were used.
Size of the plate was adapted to KM-22 housing. The front panel was made in Corel, printed on self-adhesive paper and laminated.
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Link to original thread - Konwerter USB do RS232 (wszystkie sygnały) i RS485