A new version of this project is available here
GLINK-LT is a modern clone of the Commodore VIC-1011A RS232 User Port adapter for Commodore 8-bit computers. The adapter is fully supported by the standard Commodore BASIC at up to 2400 baud. Jumpers allow the card to be configured as a UP9600 for 9600 baud operation in Novaterm and Striketerm. A reset button is also provided for added convenience.
Two MAX232 are used as RS232 level translators (U1 and U3). U2 inverts the control signals as expected by the original commodore software. R1, R2 and R3 provide reasonable default to the control lines in the case of 3-wire RS232 cable. Jumper blocks J3 and J4 enable UP9600 functionality.