July 12, 2020
It’s been a while since we published any thing new for the RC2014 architecture.
This is a simple combined ROM and RAM card designed to work with the RC2014 bus. This is an experimenters board. There is no fancy memory paging etc., it’s simple memory architecture was designed to be flexible and allow the user to experiment with other CPU architectures on the RC2014 bus. It was originally designed to work with our 8052 CPU.
- enhanced RC2014 bus
- Selectable memory* options 8K, 16K or 32K
- Board can be used as RAM only or ROM only or both.
- Options for nMRD/nMWR or nRD/nWR signals
- Option for 27C512 with Hi/Lo ROM (A15) select
- IC Decoder 74xx138 using A15/A14/A13 (with extra options for A13 & A14)
8 or 16-bit wide data bus**
- moveable memory positions (i.e. ROM can be at top or bottom memory space)
A couple of important notes:
* Both ROM and RAM memories must be the same size.
** see explanation below
The option for either nMRD and nMWR (nRD and nWR or’ed with nMREQ) signals or nRD and nWR only signals when IC3 (74xx32) is fitted or not fitted allows for experimenting with other CPU Read/Write architectures.
Notably, the enhanced RC2014 bus features a 16-bit data bus. The card can use this enhancement by allowing the selection of the high or low 8-bit portion of 16-bit data bus. This allows the user to experiment with 16-bit CPU’s such as 68000 or 8086 when two cards are used together.
It’s schematic is here
February 26, 2020
Last year Parallax released their latest multicore processor, the Propeller2 or P2X8C4M64P to give it, its full name. It’s been a very long time coming and after a few setbacks it is finally here. It’s specs are very good, featuring 8x 32-bit cores (or cogs as Parallax likes to call them), 512K RAM and 64 GPIO with SmartPin features.
I got my P2 evaluation system (ES) board a few weeks back and designed a couple of P2 ES prototyping wings to go with it.
The first prototyping wing (on the right) is a classic proto board with I/O from two GPIO ports. The other prototyping wing is a breadboard design for faster circuit build and test and features a 3x LED’s and 2x switches
I’ve got a few spare PCB’s which I’ll put on my Tindie store.
November 26, 2018
I been using a lot of TTL and CMOS logic gates in my recent RC2014 circuits and after realising that I had loaned out my much used copies of TI’s TTL Logic data books some time again and never got them back so to help me I created this quick comparison table for the common TTL and CMOS logic gates.
For completeness here’s a logic truth table:
March 26, 2018
Here’s a short list of serial terminal programs I currently use or I’ve used over the recent years:
RealTerm – my current favorite terminal program. Lots of features, including choice of binary display options: ASCII-only, Hex-only, ASCII + Hex. Send string shortcuts and so on.
TeraTerm – my previous favorite terminal program. There’s a new version, so I’m planning on trying out it for a while and see if its improved enough to replace realterm.
putty – a pretty standard serial terminal program that also includes SSH and Telnet clients.
muliterminal – as it names suggests you can setup many different terminals. I used it a lot on a recent multi-serial project where I could set up a configuration for each serial device in the project and save them. It save me time in only having to set up all the serial devices once so it proved its worth.
termite – is a very simple terminal program that just gets the job done
February 23, 2018
The Prototype card is one of the very first cards I designed for the RC2014 system.
It’s larger than a normal RC2014 card but that is intentional so you have as much prototyping area as possible for building a circuit.
It features both the classic single row pin-header for the original RC2014 pin-out and also a double row pin-header for the newer enhanced RC2014 bus pin-out.
You can find them on my Tindie store
February 25, 2017
Following on from last months post about my SoB DB9 breakout board I’ve design a few of more SoB breakout boards using the DP5050 footprint.
The first is a 2-channel Relay Board. It has two relays with LED’s to indicate when they are active. Using it is pretty easy as it features the choice of screw terminals or pin headers to interface to it.
The next is a universal RS232 breakout. I call it universal as all the pins (8 in total but not ground) from a 9-way RS232 DB9 are broken out onto pin headers. To connect up to these are the 4 signals (T1,T2,R1 and R2) from a MAX232 (or equivalent) RS232 chip. So you can swap around the transmit and receive and handshake signals as you like.
The next board is just a classic prototyping board. There’s not much too say about this board.
The last board is a symmetric power supply for rectify AC voltage into positive and negative DC supply rails. I’m hoping to use this for a audio project I’ve got in the works.
Dangerous Prototypes (DP) have a great page describing the various PCB sizes here:
As usual you can find them on my Tindie page here
January 9, 2017
Whilst looking to build some breakout boards I remembered the Sick of Beige (SoB) “standard” of PCB footprints designed by Dangerous Prototypes. DP have made a really cool set of PCB footprints in various sizes with the added bonus of being designed to be case friendly.
Dangerous Prototypes have a great page describing the various PCB sizes here:
My first Sick of Beige (SoB) board is SoB DB9, using the DP5050 footprint. This is a handy little breakout board for those wanting to build their own 9-way D-Type interfaces be it for RS232, RS485, CAN bus or any other project.
A standard 9-way D-Type (Male) connector provides the interface with 3.5mm Screw Terminals connections provided for easy interfacing. In addition a Male Pin Header connections is also provided. Two small circuit prototyping areas are also provided.
– 9-Pin D-Type connector (Male)
– Easy to Connect Headers
– 3.5mm Screw Terminals
– 2.54mm Pin Header
– small circuit prototyping area x2
– Compatible with Sick of Beigh DP5050 footprint
– Board Dimensions: 50 x 50 mm
– 3.2mm Mounting Holes x4
– Industrial Control
As usual you can find them on my Tindie page here
November 22, 2016
Despite USB being everywhere, I still use a lot of industrial and embedded interfaces, such as RS232 and RS485 interfaces, in my projects. Legacy equipment especially and even new industrial equipment still use RS232 for programming and monitoring. While RS485 interfaces can still be found a lot in industrial communications such as factory automation.
So with this in mind I felt I needed an Raspberry Pi add-on board to simplify a lot of these connections. So here is the Raspberry PIIO FieldBus add-on board. It is a multi-communications board RS232 or RS485 and CAN Bus interfaces.
The board uses 3.3V components and is completely voltage compatible with the Raspberry Pi.
The board connects directly to the Raspberry Pi’s SPI to provide CAN Bus communications and also to the UART Rx and Tx to provide RS232 or RS485 communications.
CAN Bus interface uses MCP2515 CAN controller and MCP2551 CAN transceiver IC provides CAN Bus v2.0 A/B at 1 Mb/s. It is connected the Pi’s SPI Interface. Connection is provided via a 3-Way screw terminals.
RS232 interface uses a 3.3V MAX3232 (or Equivalent IC) chip and CTS (GPIO16) & RTS (GPIO17) signals are provided. Connection is provided via an industry standard 9-Way D Connector (Male).
RS485 interface uses 3.3V MAX3485 (or Equivalent IC) chip with DE (GPIO27) & !RE (GPIO22) used to control the RS485 transceiver control signals. Connection is provided via a 3-Way screw terminals to the outside world.
The Raspberry Pi expansion port has only on UART interface available for serial communications. So where both circuits are fitted, only one RS232 or one RS485 interface may be connected to the UART, therefore only one interface can be used at any time.
You can find them on our Tindie store
June 29, 2016
This last month I’ve been working on some new add-on boards for the Raspberry Pi Zero.
In no particular order:
ADC16 – 16-ch ADC board (2x MCP3008 8-ch, 10-bit)
UserP0rt – 16-ch port expander and 8-ch ADC (MCP23S17 and MCP3008)
Relay2 – 2-ch Relay board (2x Relays 30V, 1A)
I’ve just sent these off to be manufactured, so I’ll post an update when I’ve got them back.