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2019 Radiocrafts AS
MBUS User Manual (ver 2.01)
MBUS USER MANUAL
4 Power Management
There are different ways to minimize the total current consumption and thus extend the battery lifetime for battery
operated devices. What determines the battery lifetime is how much time the module spends in the modes where
current consumption is “high”.
The Radiocrafts modules offers several configuration options to allow the module to be “off” for an extensive part of
the time:
o
Manual SLEEP function
(‘Z’-command from config mode)
o
Automatic SLEEP functions (SLEEP_MODE configuration parameter)
o
IDLE mode without listening to RF.
o
Turn off module completely (not recommended)
The details of these methods are described in the following subchapters.
4.1 Manual SLEEP function
The low power SLEEP mode is manually entered by using the SLEEP command ‘Z’ after the module is set in
configuration mode.
In SLEEP mode the module will not receive or detect incoming data, neither from the host (UART port) nor from the
air. The module is awakened from the SLEEP mode by sending the wake-up byte 0xFF on the UART RXD line
(use a UART Baud rate > 4.8 kBd due to a maximum pulse length requirement). After the module has woken up
(see Timing Information) it is ready to receive data on the UART or from the air. The SLEEP command can be used
for both Master and Slave.
All configuration settings and RAM values are retained during SLEEP.
4.2 MBUSx Automatic Sleep
It is also possible to configure the module to enter SLEEP automatically after a message has been transmitted
(SLEEP_MODE=1). With this setup the module has to enter TX-mode (transmit a message) after power-on before
entering SLEEP mode first time.
The Slave has special support for automatic sleep after data transmission. If automatic SLEEP after TX is enabled
(SLEEP_MODE = 1), the module will automatically go to sleep after data transmission, if a message is not
received. The automatic sleep is done after any message transmitted. The slave host application is responsible for
waking up the module for a re-transmission in 2-5 seconds if a communication sequence was started, but no reply
received from the master.
If automatic SLEEP after RX (and TX) is enabled (SLEEP_MODE = 3), the module will automatically go to sleep
after data reception and the message is sent to the host over the UART. This feature should normally only be used
for a Slave.
4.3 IDLE mode without listening to RF
A ‘0xFF’ byte will wake up a sleeping Slave into a low power idle mode (IDLE). The Slave will only accept UART
input (RXD UART) in this IDLE mode, not RF, to save current. The current saving depends on UART rate and
gives less current consumption for low UART rates (but data transfer takes longer time).
Error! Reference source n
ot found.
illustrates current vs time for a slave configured for auto sleep at 2.4 kBaud UART rate when receiving
acknowledge from Master after the first transmission.
