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

Datei:Interfaces 2.png

Pinout RS485 isolated

Typ	Signal	Pin	Pin	Signal
RS485	NC	1	2	D+
	ISO_GND	3	4	D-

Pinout digital IN/OUT

Typ	Signal	Pin	Pin	Signal
Isolated outputs	ISO_OUT_A0	1	2	ISO_OUT_B0
	ISO_OUT_A1	3	4	ISO_OUT_B1
Isolated inputs	ISO_IN_N0	5	6	ISO_IN_P0
	ISO_IN_N1	7	8	ISO_IN_P1
	ISO_IN_N2	9	10	ISO_IN_P2
	ISO_IN_N3	11	12	ISO_IN_P3
	GND	13	14	GND
Digital inputs	GPI0	15	16	GPI1
	GPI2	17	18	GPI3

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.

4-20mA current loop inputs

The measurement of the four loop currents is done one channel at a time by the means of a shunt resistor. The GW4101 provides a per channel current limited (30mA) 24V power supply for easy connection of external sensors.

4-20mA current loop output

The device features a 4-20mA current loop output with integrated loop supply voltage. It is internally realized using a Microchip MCP4716 10-bit ADC with I2C interface.

The following diagram shows the internal architecture of this output.

Digital inputs

The following diagram shows the internal design of the four digital inputs:

This design allows the connection of push-pull- and open-collector-outputs with a threshold of about 4.5V. It is also possible to use a mechanical switch or a relais to connect the input to GND without the need for an additional pullup resistor.

Following diagram shows a simplified design:

Isolated inputs

The following picture shows the simplified architecture one of the four isolated inputs with internal current limit and temperature stabilized threshold. Internally the isolation is achieved by the use of a TLP293 optocoupler.

Isolated outputs

The device contains a Panasonic AQW282 solid state relais to realize two independent isolated outputs. As there is no internal current limitation the user is responsible for ensuring a current flow of max. 300mA.

Linux mapping

Digital and analog I/Os (deprecated sysfs mapping)

Digital and analog I/Os (new libgpiod mapping)

Serial interfaces and busses