Maxx GW4101
the device
The programmable maxx GW4101 mobile communication gateway for industrial applications collects and processes the information from your devices, machines and sensors, and transmits it via the expanded LTE network. The sensor interface expansion enhances the basic unit with interfaces for PT100/1000 temperature sensors and the widely used 4 – 20 mA current loop interface, as well as other digital inputs and outputs. The maxx GW4101 gateway is therefore ideal for transmitting measurements from the field to the head office or the cloud.
Interfaces
Pinout RS485 isolated
Pinout digital IN/OUT
Pinout 4-20mA IN/OUT
Pinout RTD
RS485
An isolated RS485 interface is available as /dev/ttymxc1. The interface includes a switchable termination resistor.
The termination resistor is enabled by driving RS485_TERM_EN high.
Analog inputs
The GW4101 offers connection options for up to four resistive thermal devices (RTD, e.g. PT100/PT1000) and up to four 4-20mA current loop inputs.
Internally an Texas Instruments ADS1220 16-bit ADC ist used. On the Linux side the ADC is accessible via SPI bus.
The cost effective measurement circuit uses a single ADC which is multiplexed to the different measurement channel. To select a channel as well for RTD as also for loop current measurement the channel number (0-3) has to be written to RTDSEL[1..0].
RTD
The following picture shows a simplified schematic of the ratiometric measurement circuit to determine the actual resistive value of the RTD devices.
