1-wire/RS485/mV/RTC Pi HAT (short tail)
The I2C analogue input, MODBUS/RS485 and 1-wire board HAT is for use with a Raspberry PI. It provides a 1-wire bus connection, able to support multiple 1-wire devices and brought out onto screw terminals. 5v power is also fed to the 1-wire bus so devices needing power are supported as well as those that can use parasitic power. As well as the 1-wire ports, 4 x analogue input ports are also provided, each able to measure voltages within a range of ±2.5V. Gain on each channel can be individually controlled from x1 to x120. 10 bit analogue to digital conversion is performed automatically by the on board microcontroller and can be read through the I2C bus. Analogue inputs are connected via screw terminals and are protected up to 16V. +5V and ground is also brought out on the board, via screw terminals for ease of connection of external circuitry.
An RS485 input/output port is provided with auto receive/transmit switching to enable easy implementation of serial MODBUS. 1000V galvanic isolation is provided on the port and an isolated power supply can provide up to 200mA to connected sensors. The RS485 port is connected directly to the raspberry PI /dev/serial0 port. A 120R termination resistor can be selected using a jumper if needed.
As a further facility a battery backed up real time clock is provided which can be used to provide a real time source for situations where the host computer has no internet connection. Battery life is expected to be greater than 10 years.
Three LEDs indicate TXD activity (blue), RXD activity (red) and keep-alive (green).
A python library is available to access the registers of the analogue channels to read the input voltages and to set the gain of the channels. The 1-wire ports are accessible as part of the built-in 1-wire package supplied with the raspbian software build, as is the real time clock facility.
As a true Pi HAT board it simply plugs onto the extension pins of a B+ and onward. The built-in 256Kbit flash EEPROM identifies the board and self-configures it so that it is available for use without any special configuration. Special programming on the onboard microcontroller handles the I2C clock stretch issues to be found on some versions of the PI. A jumper pair allows shifting of the I2C address for the counter system to any one of 4 different addresses to avoid address clashes. Mounting pillars and screws are included in the package.
- 1 x 1-wire ports with 5V power, brought out to an RJ12 socket, with ESD protection.
- 4 x 10-bit analogue inputs, brought out to screw terminals with ESD protection.
- 1 x RS485 port with 1000v isolation and 200mA of isolated 5V power.
- Real time clock, with battery (10 year life).
- I2C bus connection
- 3 x LED (green - Heartbeat, red - Receive and blue - Transmit)
- Python library for accessing board registers and characteristics
- Solar power and heat pump monitoring systems
- Home automation
- Data centre monitoring
Manuals and Software
Manuals and python library are available below