If you
have been involved for a while in embedded electronics designs, you probably
faced the same challenges about how to validate a design using a particular
part or parts. Is the wiring correct? Is this piece of code/firmware driver
correct?
It will
turn as a costly mistake to commit a design to a prototype production run to
later find that you missed or made a wrong connection or that the software does
not work at all for that part.
Then as part as the development process you
should perform some validation. In some cases simulation helps but it may turn
to be very complex and time consuming, and after all is just that a simulation,
not the real thing.
For ages
we have been “air wiring,” using adapters, or other means to extend the
features of a particular development or evaluation board, it became very common
on FPGA based designs and later with the advent of many low cost boards such as
Arduino, Raspberry Pi, BeagleBone, Tinsy, and many more, it became more easy,
but still we had to figure how to add some extra support components required
for each part, power, etc.
One of
the vendors that started putting together an easy way to deal with this on FPGA
designs was Digilent, also when using their development boards for education,
the came out with the PMOD™ or Peripheral Module that was basically a set of
plug-in boards following a proprietary standard specification.
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| Image Courtesy of Digilent, Inc. |
Each of
the different PMODs have a specific function and included all the necessary
components to implement that function as an extension of an existing
development board. There are some guidelines on the “standard” about size but
the most important part is the pinouts for three different type of boards using
1x4, 1x6, 2x6 standard .1” headers.
Other
vendors came with similar solution, Microchip Technology at first created the PICTail and
later the PICTail+ boards, Seeedstudio with their Grove, and among them
MikroElektronika with their mikroBUS™ and Click Boards™.
The
mikroBUS™ was introduced by MikroElektronika as a way to create standard add-on
boards to their own development boards, initial add-on boards were very simple
like a set of slide switches, a pot, couple of LEDs, they made the standard
public and later in 2015 refined and republished as v2.0 covering all aspects
for implementing the mikroBUS™ “socket” & interface on development boards,
and creating the add-on boards that for their products baptized as the “Click
Board.”
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| Image Courtesy of MikroElektronika. |
Both
mikroBUS™ and Click Board™ are Trademarks of MikroElektronika.
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| Pi3 Click Shield by MikroElektronika |
Now take in account the add-on mikroBUS™ compatible or Click Boards™ are not intended to be something like and Arduino Shield, Raspberry Hat, BeagleBone cape, etc., these are very simple boards with a very specific function.
But
don’t worry, do you want to use Click Boards™ with a Raspberry Pi without
having to use wires and a prototype board? There are already several Pi Hats
with mikroBUS™ sockets, including one from MikroElektronika.
First,
the mikroBUS™ pinout, where the hardware interface is via a pair of 1 row 8
position common .1” pitch female headers. Signals on the headers are assigned
always to the same pin and are defined in three groups of communication
interfaces (SPI, UART and I2C,) six extra I/O pins some of them with the option
to have a specific function, (PWM, Interrupt capable, Analog Input, Reset and
Chip Select) and two power groups for +5V, +3.3V and GND.
While it
may feel that the number of pins and functions are limited, most of the common
devices you will find on add-on boards are covered by them. There are over to 500Click Boards™ and every day “compatible” boards are starting to pop-up in the
market.
Several
other vendors started to adopt the standard, such as Microchip Technologies,
you will find that many of the new evaluation and development boards, even the
simpler ones, include now one or more mikroBUS™ sockets.
Second,
if you want to produce your add-on board, be aware that the Click board™ is a trademark
of mikroElektronika so you are not allowed to call your board “Click” but to
claim compatibility there are some guidelines you must follow regarding board
size, silk-screen markings, etc. Many of these guidelines are not strictly
mandatory but highly recommended to preserve the overall design, and obviously
you must give credit to MikroElektronika and must place the mikroBUS™ logo on
the board silkscreen.
The full
mikroBUS™ specification is available here.
Third, placement recommendations of the mikroBUS™ socket on the main development board. While the standard does not dictate how pcb layout of the main board has to be done, there are some recommendations that will help your board use the vast collection of Click Boards™ and mikroBUS™ compatible boards available in the market today.
You can
order Click Boards™ directly from MikroElektronika or from various electronics
distributors like Arrow Electronics.
An added
benefit using MikroElektronika Click Boards™ is that MikroElektronika also
provides sample code and companies like Microchip Technology included support
code on their development tools like MPLAB Code Configuration (MCC) or Atmel
Studio Start.
I’ll be publishing
soon some projects showing how to build basic demo programs for Click Boards™
using Microchip’s MCC.
Meanwhile,
Happy Hacking !
Cheers
Jorge
Jorge
