DHT22 Slave Board for the Mercury System

• User LED: by default it is set to work in heartbeat LED mode (periodic pulses).
• Mercury Connector: used to interface with the other boards of the Mercury system.
• Address Dip Switch: sets the board’s address within the Mercury system.
• Programmer Connector: Microchip PicKit 3 programmer/debugger connector. It is wired directly to the microcontroller’s debug port, for advanced debug and programming features.

• Capture/Compare/PWM Peripherals: 2 CCP, 2 ECCP
• Timer: 4 x 8-bit, 1 x 16-bit
• ADC: 12 ch, 10-bit
• Comparators: 2
• Temperature range: -40°C ~ 125°C
• Operating voltage: 1.8~5.5 V
• Pin Count: 14
• XLP: yes

The set of boards that makes 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 for the slaves. It also carries a simple power supply and a charger for a single LiPo cell (enough for the power needs of simpler systems). It comes in different versions, depending on the microcontroller unit used.

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

• Power Board (PB): this is the board that covers the specific power needs of the system, when they arise. They vary according to the power requirement to be met (high power, solar harvesting, piezoelectric harvesting, and so on).

• Slave Board (SB): these are the peripherals of the system and vary according to the particular sensor or actuator fitted. Typical examples are SBs with relays, temperature sensors, RGB LED controllers, servo controller, accelerometer, 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. Some versions can carry a display, a battery holder, and so on.

• Brain-Less Board (BL): these are the boards without a controller. They generally hold 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 only the application-level logic to write.

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 handling the communication buses (I2C, UART) and 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:

• PML: peripheral management layer
• SSL: system services layer

OSL (Operative System Layer): this layer is a lightweight RTOS that provides the basic system services, such as scheduling tables for the various tasks, events, software 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
• Slave FW Upgrade Package
• FW Package
• MS_SB330_Datasheet
• MS_SB330_Schematic