electrodesigns.net

MECoB stands for Modular Embedded Control Board. It’s an initiative by Electrodesigns.Net to build a small, general purpose, configurable and flexible control board based on this idea. At this stage it is just an idea which may be discussed to get it matured. The idea, in brief, is to have a single carrier board with many IO boards/modules, stacked in a rack model over the carrier board and inter-connect them through a common and very simple interface bus like SPI or I2C. I am currently considering I2C because it is very simple, available in every microcontroller and does not need an additional signal like select pin as in SPI.

The MECoB may contain these modules:

1. Processor (PRO-MOD)
2. Power Supply (POW-MOD)
3. Digital Inputs (DIO-MOD) (continue reading…)

DipTrace remains free provided you don’t hit the 300 pin barrier. From a diyAudio perspective, what are the possibilities within such limit? Here are three different diyAudio boards as practical examples.
The first board hosts a PIC32MX2 coupled to a WM8731 stereo codec.
The second board is a SigmaStudio target, hosting the ADAU1701 the same way as Analog Devices EVAL-ADAU1701MINIZ.
The third board hosts a WM8580 multichannel codec delivering eight analog outputs.
The common denominator of all three boards is a 2×10 pin expansion connector allowing to stack them. A possibility is to stack PIC32MX2 acting as USB-audio device, grabbing digital audio from the PC, sending it over I2S to the ADAU1701 board. (continue reading…)

Do-it-yourself Audio is a popular topic, bringing lots of enthusiasts. What would you do without digital audio nowadays?

You can build your own diyAudio kit using the PIC32MX2 Breakout Board hosted here on electrodesigns.net and the mikroE Audio Codec Board. The mikroE Audio Codec Board is equipped with a WM8731 codec chip featuring a full duplex I2S interface and stereo 24-bit oversampling sigma delta ADCs and DACs. The analog outputs can operate at different listening volumes. For the sake of simplicity, mikroE only wired the single mike input and the buffered headphones outputs. The WM8731 requires an additional communication (SPI or I2C) for defining the listening volumes and other settings, however mikroE wired and labelled the concerned pins for I2C only.

Following is a concrete proposition for connecting a mikroE Audio Codec Board on a PIC32MX2 Breakout Board.  Such audio setup, exploiting the mike input and the headphones outputs, beats the Microchip PIC32MX1/MX2 starter kit. The audio signal presented at the mike input gets digitized by the WM8731, gets processed by the PIC32 in realtime, gets converted back to analog by the WM8731, and gets finally presented at the headphones outputs. On top of this, the PIC32MX2 USB connectivity allows experimenting with the USB-audio protocol.

The image shows the two boards interconnects. Other layouts may exist thanks to the PIC32MX2 pin multiplex.

The PIC32MX2 series has at least one advantage over PIC32MX1 series that it has built-in USB. This makes it perfect for small DAQ projects and peripheral interfaces to the standard PC. The breakout board is similar to the previous PIC32MX1 Breakout Board and Stellaris LM3S811 Breakout Board. Gerbers and complete design (CAD) files are available for download.

Download Files:

The LM3S811 Breakout board is design with the same spirit of PIC32MX1 Breakout Board to make easy to get started. Stellaris is the microcontroller family initially designed by Luminary Micro (LM). LM was acquired by TI, thanks to the recession of 2009-on-wards. It’s a very promising family. TI has included some other members into family including the floating point LM4F based series. The JTAG connector may seem “too big” but this was to keep it compatible with the actual connectors coming from TI; like this board be used along-with LM3S8962 demo kit and same kit can be used to program this board.

Download Files:

Often a complete embedded design is split into smaller modules for more flexibility. In this way, the system can be upgraded only by upgrading one of its required part. The best practice is to split the design into two major parts:

1. Base board or the carrier board or an expansion board
2. Processor board or plugin module

The base board if often designed with maximum peripherals and IO options to be used in future applications. The common peripherals like Ethernet, USB, RS485; storage like flash, microSD and other options are populated. A common connector interface through headers is provided where the Processor board seats. Here is an example of such a system. A good base board for simple automation and control applications may contain:

1. Ethernet
2. USB
3. Serial such as RS232/485
4. microSD slot
5. Flash memory with an interface like SPI
6. Stereo input/output
7. On-board temperature sensor
8. Power supply unit
9. Joystick
10. A display like LCD, OLED or TFT
11. Clock/calendar chip on I2C bus
12. Some relays
13. Digital and/or analog outputs
14. Output power for IOs like sensors

The processor board, as the name describes, carries the main CPU like a microcontroller and is the brain of the system. The designer can change the processor board as the requirement changes.

The major disadvantage of this kind of scheme  is the production cost as an application may carry un-necessary on-board components. This approach is, though, great for small production, prototyping and for a range of products which shares similar features. For example an industrial controller with variety of options in different versions can be offered to customers. It is easier to maintain for small companies and can relatively easily be modified.

The other idea, which is very different from above one, is to use a back-plane like those used in PLC. The idea is use a common serial bus and connect/attach all the system modules on the very bus. The system modules may include power supply unit, main CPU unit, IO unit, communication module and several others as per requirement. In this way the user can control his cost by selecting appropriate set of modules. This also frees the manufacturer from repetitive system revision, rather the vendor only upgrades, or provide better option than the existing one.