Eight 24-Bit Analog Inputs DAQ 8-Layer Stackable HAT for Raspberry Pi

Raspberry Pi has no analog signal processing capability. This HAT can read eight differential or common ground analog signals with 24-bit precision and up to 64kBPS data rate. Up to eight cards can be stacked on top of one Raspberry Pi. When multiple cards are stacked, the master card can send the clock and sync signal to all slave cards, allowing synchronized data acquisition over all the channels. It also has an RS-485 port, a power LED, and a push button that can be used to shut down the Raspberry Pi. Pluggable connectors make the card easy to use when multiple cards are stacked.

Stackable to 8 levels, the card works with all Raspberry Pi versions, from Zero to 5.

Two of the Raspberry Pi’s GPIO pins are used for I2C communication, and another pin is allocated for the interrupt handler, leaving 23 GPIO pins available for the user. The RS485/MODBUS port permits almost unlimited expandability. The onboard Real-Time Clock with battery backup keeps the time indefinitely in case of power failure. Last, a hardware watchdog can power cycle the Raspberry Pi in case of software lockup. TVS diodes on all inputs protect the card from external ESD, and an onboard resettable fuse prevents accidental shorts. The card can be powered from a 5V/5A or a 12V-24VDC power supply. In both cases, it provides up to 4A continuous and 5A peak to the Raspberry Pi.

Compatibility:  The Eight 24-Bit Analog Inputs card is compatible with all Raspberry Pi versions from Zero to 5.

Power Requirements: The Eight 24-Bit Analog Inputs card needs 5V to operate and can be powered from its 2-pin pluggable connector. The card draws 50mA. If power is applied to the 2-pin pluggable connector, no other power supply is needed for the Raspberry Pi.

LED Indicators: A power LED shows when power is applied to the board. Eight LEDs show the status of groups of 8 inputs. The software can select inputs 1-8 or 9-16.

DIP Switch Configurations: A six-position DIP switch is used to select the source of the RS485 port and the card’s position in the stack if multiple cards are used. The left-most position is the RS485 terminator. Set this switch ON if the card is the last on the RS485 chain. The following two positions select the source of the RS485 port. Set the switches ON to drive the RS485 from the Raspberry Pi or OFF to drive the port from the local processor.

Stacking Multiple Cards: Up to eight cards can be stacked on your Raspberry Pi. The three positions of the configuration DIP Switch, labeled ID0, ID1, and ID2, select the stack level. Cards can be stacked in any order.

Reset Pushbutton: Shutting down the Raspberry Pi by turning off the power can result in SD Card failure. A shutdown command must be used before the power cut-off to prevent this. However, this requires a monitor, keyboard, and mouse connected to the Pi. A momentary push button installed at the edge of the card provides a convenient way to shut down the Raspberry Pi. The button is routed to pin 37 (GPIO 26). You must write a script that monitors this pin and issues the shutdown command if pressed for more than a desired time.

Card Layout

Electrical Specifications

• Power Supply: 5V/8A pluggable connector
• On board resettable fuse: 4A
• Maximum input signal: 3.3V
• Programmable gain: 1 to 128
• Minimum input signal: 25mV full scale
• Maximum data rate: 64.4 kSPS at 80 dB dynamic range
• Minimum input impedance 1MΩ for gain > 8
• Power consumption max. 50mA

Mechanical Specifications

Featurres

• Eight 24-Bit Analog Inputs DAQ 8-Layer Stackable HAT
• All inputs are differential with or without a common ground
• Eight-layer stackable to 64 differential analog inputs
• Software selectable inputs: ±0.18V, ±0.37V, ±0.75V, ±1.5V, ±3V, ±6V, ±12V, ±24V
• Wide range power supply: 5V or 12V-24V
• Provides 4A continuous, 5A peak power to Raspberry Pi
• RS485/MODBUS port
• Uses two ADS131 24-bit Delta-Sigma ADCs from Texas Instruments
• Input impedance 300KΩ to 1MΩ
• Data rates up to 64 kSPS
• Internal or external, software-selectable clock and trigger
• Hardware watchdog can power cycle the Raspberry Pi
• Real Time Clock with battery backup
• Uses only the I2C port, all GPIO pins available
• Eight LEDs with a programmable threshold for input status
• Pluggable Connectors 26-16 AWG wires
• General-purpose pushbutton
• Works with any Raspberry Pi from ZERO to 5
• ECCN Code EAR99
• Command Line Driver
• Python Library
• Node-Red nodes
• OpenPLC module
• CODESYS Library
• MODBUS Interface

Software: You can write your application using the Command Line or the Python Library provided. No programming is required if you use Node-Red. You can drag-and-drop the functional blocks to design your application.

Accessories

• Din-Rail Mounting
• The card can be installed parallel to a DIN rail using the DIN Rail Kit Type 1 or perpendicular using the DIN Rail Kit Type 2.

What’s Included:

When you purchase the 16 Universal Inputs Card, you will receive the following items:
1. 16 24-Bit Analog Inputs Card for Raspberry Pi

Mounting hardware

• Four M2.5x18mm male-female brass standoffs
• Four M2.5x5mm brass screws
• Four M2.5 brass nuts

Mating connector plugs

Quick Start

1. Plug your Eight 24-Bit Analog Inputs card on top of your Raspberry Pi and power up the system.
2. Enable I2C communication on Raspberry Pi using raspi-config.
3. Install the card software from github.com:

• ~$ git clone https://github.com/SequentMicrosystems/24b8vin-rpi.git
• ~$ cd /home/pi/24b8vin-rpi
• ~/14b8vin-rpi$ sudo make install
• ~/24b8vin-rpi$ 24b8vin -h

The program will respond with a list of available commands.