February 15, 2017 15:01
How to add an external power switch to your Creator Ci40
Connecting an external power switch to the Creator Ci40
The Creator Ci40 platform, available at RS now, is designed to allow developers to easily create connected projects based on MIPS hardware. To find out more about the Creator Ci40 check out www.creatordev.io
Building the Creator Ci40 board - RS Part 125-3306 into an enclosure may require controlling the power to the board remotely. This article looks at passive and active options for controlling the DC power supply to the board.
The Creator Ci40 has been designed with a header, CN11, that specifically provides a mechanism for controlling the DC power input from CN16.
(Note CN11 does not control the USB power path. If you are powering your Ci40 via USB a separate control mechanism is required.)
CN11 allows easy access to the enable line of the input DC/DC buck convertor (PSU).
The control states of CN11 are shown in the table below.
The picture below shows the location of CN11 and which signals are which.
Using a passive rocker switch
The figures below show a simple ON/OFF switch attached to the Creator Ci40 board. CN11 is cabled to a remotely mounted rocker switch using a custom two wire cable. Since the switch is only controlling the PSU enable signal, the current is only a few mA. This means that many types of switch can be used to control the PSU enable.
Using an active switch
Though not implemented in this article it is also possible to remotely control the Ci40 power from an active source, such as another processor board, timer or PC, using the same CN11 header.
If using an active switch then the control signal driving into CN11 need to be isolated for correct operation and to prevent any possible damage.
Note: The enable line must not be driven directly from 3v3 logic.
Example interface circuits are shown below:
Happy creating from the Creator Team
Paul Evans joined Imagination Technologies in January 2012 and is now a Director of Business Development. Prior to joining Imagination, Paul worked for Altera Corporation for 11 years in marketing. He holds a BEng in digital electronic engineering from the University of Kent at Canterbury in England.