Dual Expansion Board for the Mercury System

The set of boards that make up the Mercury System is organised into the following “families”:

• Base Board (BB): This is the “brain” of the whole Mercury System and holds the main logic unit, several communication buses and the connectors that interface the slaves. It also carries a simple power supply and a charger for a single LiPo cell (enough to meet the power requirements of simpler systems). It comes in different variants, depending on the microcontroller unit fitted.

• Modem Board (MB): this is the board that provides network connectivity. It comes in different variants, depending on the network interface (GSM / GPRS, Wi-Fi, BT, radio and so on). It is interfaced to the base board over a dedicated serial line.

• Power Board (PB): this is the board that covers the system’s particular power requirements, where they arise. They vary according to the specific power need to be met (high power, solar harvesting, piezoelectric harvesting, etc.).

• Slave Board (SB): these are the system’s peripherals and vary according to the specific sensor or actuator fitted. Typical examples are SBs with relays, temperature sensors, RGB LED controllers, servo drivers, accelerometers and so on. They talk to the BB over I2C or UART with a dedicated command set.

• Expansion Board (EB): these are the boards that allow Mercury boards to be connected side by side. There are variants that can carry displays, a battery holder and so on.

• Brain-Less Board (BL): these are the boards without a controller. They generally carry very simple sensors or actuators that do not need the bus interface. They are an alternative to slave boards for applications that have to keep costs down.

The Slave Boards and the Modem Boards come pre-programmed with firmware that implements a dedicated command set for high-level control, while the Base Boards carry a software framework that provides all the low-level services (operating system, peripheral drivers, system services and so on), leaving the user with nothing to write but the application logic.

HAL (Hardware Abstraction Layer): the purpose of this layer is to hide the hardware dependencies from the layers above.
SML (System Management Layer): the purpose of this layer is to provide services for managing the communication buses (I2C, UART) and for managing the Modem Board (WiFi, BT, GSM / GPRS). It also provides a set of system services such as System Power Management, RTCC, USB terminal and so on.
It is split into two main components:

OSL (Operative System Layer): this layer consists of a lightweight RTOS that provides the system’s basic services, such as the scheduling tables for the various tasks, events, SW timers, alarms and so on.

There are several sub-families of Slave Board:

• Sensor Slave Board
• Actuator Slave Board
• Communication Slave Board
• Interface Slave Board
• Special Slave Boards

The table below gives some examples for each sub-family:

• Mercury System Getting Started Guide IoT and Connectivity Made Simple
• MS_EB110_Datasheet
• MS_EB110_Schematic