Apple-1 UART & Wi-Fi modem
by Claudio Parmigiani PURPOSE Allow the Apple-1 computer (and Replicas) to handle connections with telnet protocol (either outgoing or incoming) in order to connect to existing BBSes or chat sessions (keyboard-to-keyboard) IMPLEMENTATION An Asynchronous Communications Interface Adapter ( ACIA ) 6551 has been used. It was commonly used as an UART (Universal Asynchronous Receiver-Transmitter) for the 6502 microprocessor; it is addressed through a 74154 (4 to 16 lines decoder/demultiplexer). UART is then connected to an ESP8266 that acts as an Hayes-compatible Wi-Fi Modem. The ESP8266 must be programmed following the instructions: https://1200baud.wordpress.com/2017/03/04/build-your-own-9600-baud-c64-wifi-modem-for-20/ A small Terminal program written in Assembly is used to interact with it. CIRCUIT & ADDRESSING Power is derived from the 5V main bus. 74154 acts as Address Decoder as described below. Apple-1’s Address lines from A12 to A15 ( A15 is MSB) are co