Copyright © Shimmer 2017
Realtime Technologies Ltd Shimmer User Manual
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51
6.2.2. MicroSD Card Storage
MicroSD Card Socket
The Shimmer3 mainboard contains a microSD card socket to incorporate extra memory resources.
For Shimmer compatibility, the microSD card chosen must implement 1-bit SPI mode. Please refer to
the Shimmer3 MicroSD Media Guide for more information on microSD card compatibility. A
compatible SD card is shipped with each Shimmer3.
Host Data bypass Functionality
To improve usability, Shimmer incorporates a wide bandwidth analogue MUX and tri-state logic
buffering on certain signals routed to the external connector to provide direct and immediate access
to flash memory using an external SD-flash card controller (SDHOST) for high-speed data transfer.
Shimmer Applications that use the microSD card will require firmware that allows for the SD
specification's requirement of a power-cycle to change from SPI mode (the card talking to the
MSP430) back to SDIO mode (the card is controlled by the USB flash media controller). Power-cycling
the card requires explicit control of the card's interface pins, setting them to LOW (zero Volts).
The Host Data Bypass implementation has been simplified when compared to prior generation
sensor platforms such as Shimmer2r. When a firmware application detects that the Shimmer is
docked, it can complete pending activities, power cycle the flash media (including lowering all SPI
pins going to the media), reconfigure the data path and the assert a media-detect signal to the host
computer via a USB flash media controller peripheral.
Always use a Shimmer Dock v3 (or higher) for best performance.
Earlier docks required a logic timing-critical scheme, which has been deprecated.
The Host data activity indicator on the USB Reader dock, presented earlier in this manual, provides
helpful status information.
6.2.3. Power
The Shimmer units are supplied with a 3.7V 450mAh re-chargeable Lithium battery but the design
supports both Lithium-Ion/Lithium-Poly cell chemistry and lithium coin cells and alkaline batteries.
Device safety is maintained by integrating battery polarity protection, charge monitoring and failsafe
battery over/under voltage and over-discharge limits in common mobile environments and while
AC-powered. Refer to the Section 3.5.3 for further details on use of replacement batteries with
Shimmer.
Power States
A sliding switch is used to control board power states.
Soft power switching is provided for the Bluetooth radio module, temperature compensated crystal
oscillator, FFC expansion (Radio Peripheral) and microSD socket (see Host Data bypass Functionality
discussion above for more information on microSD card power control). Other modules have
integrated shutdown functionality.
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