ThingMagic Mercury xPRESS Platform v1.7 - Manual (Page 123)

A D I V I S I O N O F T R I M B L E
Hardware Reference Guide 123
Comm Bus, the AC, Battery, and USB power sources are disconnected. They remain
connected to each other, so the battery will be charged in the background, but will not be
able to power the system.
Known HW Limitations
The hardware has some known limitations:
1. Peripheral devices connecting to V3R3 are sharing with the processor. There is
330mA current limit on that power bus that is shared with the MCU. Users should be
aware of the power consumption when adding peripherals. In order to consume
larger amounts of current, users can tap into the RFID modules power bus and add
their own voltage regulator.
2. USB Vbus cannot be monitored when the xPRESS Reader is in USB host mode.
U11 disconnects V_BUS from the USB +5V line to avoid cross connecting USB 5V to
the 3.7V battery voltage. With no battery installed, this means V_BUS goes to 0V,
triggering the SAM3’s USB voltage monitor -- be prepared to see spurious Vbus
errors.
3. USB On-the-Go functionality is untested and can’t be considered as functional.
4. The MercuryAPI doesn’t yet have a portability layer for threading and so
Asynchronous Reads do not function.
5. The use of the RTC has not been tested.
6. The onboard MicroSD card has not been tested.
7. Upgrading the firmware on the RFID module requires a separate connection to the
RFID module and is driven by the host.
8. USB suspend mode has not been tested or implemented.
Known Issues
There are a couple of known issues with this release.
1. Commenting out #define confINCLUDE_TM_READER in conf_xpress_reader.h
causes Eclipse debugging to fail (debugger disconnects immediately after loading
the image.)