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ECB PropIO V2
A Propeller-based peripheral support board for the N8VEM ECB processors.
The PropIO is a peripheral support board for the N8VEM projects based on the Parallax Propeller P8X32A MCU as an intelligent I/O controller. The Propeller MCU is ideally suited to this role as it allows for simple connection of multiple peripheral devices and utilizes a custom EEPROM based firmware that can be enhanced over time.
The PropIO V2 is intended to interface with a host processor/controller on the ECB bus such as the N8VEM SBC. The onboard EEPROM firmware of the board must be programmed with the correct firmware for the host processor/controller being used. The host software/firmware and the Propeller EEPROM firmware must act cooperatively using a prearranged protocol to communicate. At present, the pre-built PropIO V2 EEPROM firmware is intended to work with a host processor/controller running the RomWBW firmware.
Note that the PropIO V2 does support a standalone operation mode in which it can be powered by a +5V DC Jack without being connected to an ECB bus. The idea is that it would be possible to create a Propeller firmware allowing the board to act independently of a host controller – perhaps acting as a simple single board computer or terminal emulator.
The PropIO V2 supports the following peripherals:
- VGA Monitor: A DB-15 VGA monitor connector is provided and the board will drive any standard VGA monitor. The Propeller is capable of a variety of text and graphics modes. However, the current firmware implements standard 80×25 text.
- PS/2 Keyboard: A standard PC compatible PS/2 keyboard connector is provided and supports buffered keyboard input.
- SD Card: A Mini-SD Card connector is provided which allows block I/O with any standard SD, SDHC, or SDXC memory card. A host would typically utilize the SD Card to provide a solid-state disk drive.
- RS-232 Serial Interface: A 10 pin header is provided to support standard RS-232 serial connections. The header requires a pigtail to convert to a standard RS-232 connector. The serial port is a simple 3-wire interface (send, receive, ground). No flow control is supported, however the Propeller firmware does implement a small buffer. In the present firmware, the serial port is not addressable by the host controller, but can be used for in-situ programming of the Propeller EEPROM firmware as described below. A future firmware upgrade will allow the host processor/controller to utilize this serial port.
- Speaker: A small, low fidelity speaker is provided to allow generation of simple sounds. This is mostly intended to allow for various “beep” codes as desired. The current firmware does not allow the host processor/controller to directly control the speaker, but this should be possible with a simple upgrade to the onboard EEPROM firmware
Version V2 of the PropIO is a significant redesign of the original version and combines features of the original V1 with the ParPortProp. The following architecture changes were made in V2:
- Hardware latch to assert the ECB /WAIT signal
- Adds an onboard speaker
- Adds an onboard RS-232 port
- Switches the SD Card port from a Micro-SD socket to a Mini-SD socket
- Allows standalone operation powered directly by a +5V jack
- Removes the second Propeller chip
- Removes the breadboarding area
Complete documentation of this board is available here.
Supporting technical files are available here.