CoCoWiFi

The CoCoWiFi is a cartridge expansion board for the Tandy Color Computer. Its main purpose is to give the Color Computer access to the internet via WiFi. Additionally, the board contains a real-time clock, mass storage interface, 4 megabit parallel flash chip, and serial flash chip. The board is designed to fit into a cartridge case the same size as an FD501 or CoCoSDC.

CoCoWiFi contains a soft UART which communicates with the onboard ESP32 module. It is backward compatible with the SC6551 UART in the original Tandy RS232 Pak for the CoCo. This means that any software or device driver written specifically for the RS232 Pak will be compatible with this board. The problem with the SC6551 is that it is limited to a maximum bit rate of 19.2 kbps unless you use an external baud rate generator. Even with an external BRG the SC6551 is not capable of bit rates > 125 kbps.

The soft UART incorporates a special ‘native mode’ switch which enables the ‘Super 6551’ mode. In this mode the UART is able to run at bit rates up to 2 Mbps and it incorporates a 256-byte FIFO receive buffer with a variable trigger level for generating the interrupt on receive data register full. For all intents and purposes, this greatly reduces the interrupt overhead for the reception of high speed data. Instead of interrupting the host CPU for each byte received, the soft UART can wait until xx characters have been received and stored in the FIFO before interrupting. When the host CPU receives the interrupt it can read some or all of the bytes stored in the FIFO within a single interrupt service. For this reason it has been estimated that bit rates upward of 2 Mbps can be achieved under either NitrOS9 or DECB on a CoCo 3.

CoCoWiFi also incorporates a Dallas Semiconductor DS3231 real time clock that is compatible with other popular RTCs used in the past for the CoCo. The RTC module also includes 1K of EEPROM.

An additional TTL level serial port is included on CoCoWiFi that will also follow the ‘Super 6551’ standard. This could feasibly allow connection to an external Drivewire server if needed.

The development of CoCoWiFi is a work in progress. As certain features are enabled, this page will be updated to reflect the status.