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
| 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
| Typ | Signal | Pin | Pin | Signal |
|---|---|---|---|---|
| 4-20mA current loop output | OUT+ | 1 | 2 | GND |
| 4-20mA current loop inputs | IN_P1 | 3 | 4 | IN_P2 |
| IN_N1 | 5 | 6 | IN_N2 | |
| GND | 7 | 8 | GND | |
| IN_P3 | 9 | 10 | IN_P0 | |
| IN_N3 | 11 | 12 | IN_N0 | |
| GND | 13 | 14 | GND |
Pinout RTD
| Typ | Signal | Pin | Pin | Signal |
|---|---|---|---|---|
| NC | 1 | 2 | NC | |
| RTD | RTD_A0 | 3 | 4 | RTD_B0 |
| RTD_A1 | 5 | 6 | RTD_B1 | |
| RTD_A2 | 7 | 8 | RTD_B2 | |
| RTD_A3 | 5 | 6 | RTD_B3 |
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)
| Pin | Linux mapping | Typ |
|---|---|---|
| ISO_OUT0 | /sys/class/gpio178 | isolated digital outputs |
| ISO_OUT1 | /sys/class/gpio173 | |
| ISO_IN0 | /sys/class/gpio176 | isolated digital inputs |
| ISO_IN1 | /sys/class/gpio174 | |
| ISO_IN2 | /sys/class/gpio172 | |
| ISO_IN3 | /sys/class/gpio177 | |
| GPIN0 | /sys/class/gpio197 | digital inputs |
| GPIN1 | /sys/class/gpio203 | |
| GPIN2 | /sys/class/gpio194 | |
| GPIN0 | /sys/class/gpio197 | digital inputs |
| RS485_TERM_EN | /sys/class/gpio175 | RS485 termination resisitor |
| RTDSEL0 | /sys/class/gpio205 | analog channel select |
| RTDSEL1 | /sys/class/gpio202 | |
| ADC_DRDY_n | /sys/class/gpio206 | ADC IRQ |
Digital and analog I/Os (new libgpiod mapping)
Serial interfaces and busses
