User's Manual

User Manual
SM3000 OEM module
Functional description
The interface on the module enables a full-duplex message oriented communication protocol. It uses 6 (six)
IO lines, 2 data – and 4 control lines. The control lines are used to provide a hardware flow control
mechanism for the communication of a single message. A message is formatted according the SPP protocol
which is described in a separate document
1
. Having an SPP formatted message enables error checking and
message synchronization.
The module is a battery operated device which preserves energy by entering an low power mode of
operation whenever it has no action to perform. In LPM the serial receiver is disabled and if the connected
host wants to communicate it needs to wake up the module. The module will respond if it is ready to receive
a message. To facilitate this the interface uses the RTS and CTS control lines. The host signals the module it
has data to send by pulling the RTS line low. If this is detected by the module it will pull the CTS line low
indicating it is ready to receive.
The same mechanism is provided for communication from module to host. This enables the possibility for
also the host device to enter a energy efficient sleep mode. The DTR and DSR control lines are used in this
case. If the module has data to send to the host it will pull the DSR line low to wakeup and signal the host.
The host must pull the DTR line low when it is ready to receive a message from the module. If the module
detects a low DTR line it will start transmitting a single message.
These mechanisms are specified in detail in the following sections.
Serial port(UART) settings
The following serial communication settings are used
Speed 115200 baud
Data bits 8
Parity None
Stop bits 1
Host to SM3000 transmission
If the host has data to send it will pull down its RTS line. If detected the module will pull its CTS line low
allowing the host to send its message. As soon as the message is transmitted the host will pull it RTS line
high again. The module will pull its line high if it received a complete message.
1 Kernel_Serialport protocol_1.0.x.pdf
16/27 Ambient Systems B.V.