User Manual
iM871A Wireless M-Bus
Module Firmware
iM871A_WMBus_UserManual.docx, Wireless Solutions, v1.2
Page 14
3.2
Serial Interface
The iM871A can be controlled and configured via serial Interface (UART). On inquiry the
module can also be driven by Serial Peripheral Interface (SPI).
3.2.1
Connection Settings
The UART baud rate which is required for communication between host controller and radio
module is 57600 baud. Further 8 data bits, 1 stop bit and no parity bit have to be
configured.
3.2.2
Host Controller Protocol
The iM871A offers the user a host controller interface (HCI) and uses a specific host
controller message protocol With this message based serial protocol the user is able to
connect the iM871A radio module to a host system. It can be used for configuration, data
exchange and device control. Each message to or from the radio module is embedded in a
specific message frame.
SOF
Control
Field
MsgID
Field
Length
Field
Payload
Field
CRC16
8 Bit
8 Bit
8 Bit
8 Bit
n * 8 Bit
16 Bit
Msg Header
Field
24 Bit
Figure 3-10: Message format on serial interface
3.2.3
General Device Functions
Ping Request
This function can be used to check the wired communication interface (HCI) and if the
connected device is alive. If a “Ping Command” message is received the device answers
with a “Ping Response” message.
Reset Request
This function can be used to perform a software reset of the iM871A firmware.
Note: In this chapter only a short summary of the serial interface commands is
given. For detailed information please refer please refer HCI specification [3].
