# PW31-AC RS485 Wi-Fi Serial Device Server (AC Power)

> RS485 Wi-Fi serial device server with AC power, 2.4/5 GHz networking, and bidirectional Modbus TCP/RTU conversion.

- **URL**: https://www.iiotsys.net/products/pw31-ac-rs485-wi-fi-serial-device-server-ac-power
- **Markdown**: https://www.iiotsys.net/products/pw31-ac-rs485-wi-fi-serial-device-server-ac-power.md
- **Model**: PW31-AC
- **SKU**: IIS-SG-PW31-AC
- **Price**: $32.00 USD
- **Category**: Industrial Gateways & Serial Servers

## Overview

The IIoTSys PW31-AC connects one RS485 serial interface to a 2.4 GHz or 5 GHz Wi-Fi network. It uses an Andes Core processor at 160 MHz, 2 MB Flash and 352 KB SDRAM as listed in the manual, with FreeRTOS. This AC-powered variant accepts 100–240 VAC, 50–60 Hz.

The wireless interface supports IEEE 802.11 a/b/g/n and STA, AP, or simultaneous AP+STA operation with an SMA external antenna connection. AP+STA is not a Wi-Fi relay: the AP and STA interfaces must use different IP subnets, and the STA should remain connected to a router to avoid scanning-related disruption.

TCP, UDP, MQTT, HTTP, WebSocket, and virtual serial port modes provide serial data connectivity. Modbus TCP and Modbus RTU conversion is bidirectional and includes timed acquisition and data format conversion. Serial framing supports 7 or 8 data bits, 1 or 2 stop bits, None/Even/Odd parity, and software Xon/Xoff flow control.

Configuration is available through HTTP Web pages, serial CLI, XML import, Telnet, companion configuration software, and app-based Wi-Fi provisioning. The manual lists TLS 1.2, AES-128, and DES3, registration and heartbeat packets, remote parameter management, and wireless OTA updates. The enclosure measures 102.03 × 64.95 × 27.50 mm, mounts on a C45 guide rail, and operates from −40 to +70 °C.

## Description

RS485-to-dual-band Wi-Fi serial device server with 100–240 VAC, 50–60 Hz input. Supports Modbus TCP/RTU conversion and TCP, UDP, MQTT, HTTP, WebSocket, and virtual serial port connectivity.

## Specifications

- Model: PW31-AC
- SKU: IIS-SG-PW31-AC
- Product type: RS485-to-Wi-Fi serial device server / protocol gateway
- CPU: Andes Core @ 160 MHz
- Memory: 2 MB Flash / 352 KB SDRAM (manual terminology)
- OS: FreeRTOS
- Serial interface: 1 × RS485
- Serial terminals: Pin 5: B−; pin 6: GND; pin 7: A+
- Serial wiring: Connect A+ to A+ and B− to B− using a twisted pair; a shared GND is recommended under interference.
- RS485 bus capacity: Up to 32 terminal devices
- RS485 communication distance: Up to 1200 m, as stated in the manual; installation dependent
- RS485 termination: 120 Ω termination; the manual generally recommends termination for wiring over 300 m
- Baud rate: 300–230400 bps (manual serial table labels this row “TTL”; external-interface applicability needs confirmation)
- Data bits: 7 / 8
- Stop bits: 1 / 2
- Parity: None / Even / Odd
- Flow control: Software Xon/Xoff; no hardware flow control
- Wi-Fi standards: IEEE 802.11 a/b/g/n
- Wi-Fi bands: 2.4 GHz and 5 GHz; selectable 2.4 GHz, 5 GHz, or dual-band configuration
- Wi-Fi frequency ranges: 2.412–2.484 GHz; 5.17–5.25 GHz (U-NII-1); 5.725–5.835 GHz (U-NII-3), as listed in the manual
- 5 GHz channels: 36, 40, 44, 48; 149, 153, 157, 161, 165
- Wi-Fi operating modes: STA / AP / AP+STA
- AP+STA limitations: AP and STA must use different IP subnets. No Wi-Fi relay. Keep STA connected to a router to avoid AP disruption during scanning.
- Wi-Fi security: WEP / WPA-PSK / WPA2-PSK
- Wi-Fi encryption: WEP64 / WEP128 / TKIP / AES
- 2.4 GHz transmit power: 802.11b: +15 ± 1.5 dBm at 11 Mbps; 802.11g: +13 ± 1.5 dBm at 54 Mbps; 802.11n: +13 ± 1.5 dBm at HT20 MCS7
- 5 GHz transmit power: 10 dBm at OFDM 54 Mbps, HT20 MCS7, and HT40 MCS7
- 2.4 GHz receive sensitivity: 802.11b: −87.5 dBm at 11 Mbps CCK; 802.11g: −73.5 dBm at 54 Mbps OFDM; 802.11n: −72.5 dBm at HT20 MCS7
- 5 GHz receive sensitivity: −73.5 dBm at 54 Mbps OFDM; −72 dBm at HT20 MCS7
- Antenna interface: SMA external antenna connection
- Network protocols: IP, TCP, UDP, DHCP, DNS, ARP, AutoIP, ICMP, NTP, WebSocket, Telnet, HTTP Client, MQTT, Modbus TCP
- Uplink modes: TCP / UDP / MQTT / HTTP / WebSocket / virtual serial port
- Industrial protocol: Bidirectional Modbus TCP ↔ Modbus RTU conversion; timed acquisition; data format conversion
- Transport/data security: TLS 1.2 / AES-128 / DES3
- Connection maintenance: Registration packets and heartbeat packets
- Configuration: HTTP Web interface, serial CLI, XML file import, Telnet, companion configuration software, and app-based Wi-Fi provisioning
- Web interface: HTTP configuration pages; customizable HTTP pages
- Remote management: Cloud-platform remote management and parameter configuration
- Firmware update: Wireless OTA via Web interface or companion configuration software
- Indicators: Net: Wi-Fi/network status; Active: serial activity; Power: supply status; Link: server communication-channel connection
- Buttons: Reload: short press for app-based Wi-Fi provisioning; hold >4 s and release to restore factory settings. Reset: hardware reset.
- Power input: 100–240 VAC, 50–60 Hz
- Power terminals: Pin 1: L; pin 2: N
- Working current: Approx. 200 mA, as listed in the family table; measurement conditions unspecified
- Power dissipation: <700 mW, as listed in the family table; measurement conditions unspecified
- Operating temperature: −40 to +70 °C
- Storage environment: −40 to +85 °C; 5–95% RH, non-condensing
- Dimensions: 102.03 × 64.95 × 27.50 mm
- Mounting: C45 guide rail / DIN-rail mounting

## Protocols

- Wi-Fi (native): IEEE 802.11 a/b/g/n; 2.4 GHz / 5 GHz; STA / AP / AP+STA
- RS-485 (native): Pin 5: B−; pin 6: GND; pin 7: A+
- Modbus RTU/TCP (convert): Bidirectional conversion, timed acquisition, and data format conversion
- MQTT (native): Uplink communication mode
- TCP (native): Serial data uplink
- UDP (native): Serial data uplink
- HTTP (native): HTTP Client uplink and HTTP Web configuration
- WebSocket (native): Uplink communication mode
- Virtual serial port (native): Serial connectivity mode
- IP (native): Network stack
- DHCP (native): Network stack
- DNS (native): Network stack
- ARP (native): Network stack
- AutoIP (native): Network stack
- ICMP (native): Network stack
- NTP (native): Network stack
- Telnet (native): Parameter configuration
- TLS 1.2 (native): Security protocol listed in the manual

## Features

- One RS485 serial interface with 2.4 GHz / 5 GHz Wi-Fi connectivity
- IEEE 802.11 a/b/g/n; STA, AP, and AP+STA modes; SMA external antenna connection
- Andes Core @ 160 MHz; 2 MB Flash / 352 KB SDRAM; FreeRTOS
- TCP, UDP, MQTT, HTTP, WebSocket, and virtual serial port modes
- Bidirectional Modbus TCP ↔ Modbus RTU conversion, timed acquisition, and data format conversion
- 7/8 data bits; 1/2 stop bits; None/Even/Odd parity; software Xon/Xoff
- RS485 bus supports up to 32 terminal devices and up to 1200 m communication distance, subject to installation conditions
- Web, serial CLI, XML import, Telnet, companion configuration software, and app-based Wi-Fi provisioning
- TLS 1.2, AES-128, and DES3; registration and heartbeat packets
- Remote parameter management and wireless OTA firmware updates
- Net, Active, Power, and Link indicators; Reload and Reset buttons
- −40 to +70 °C operation; C45 guide-rail mounting
- AC power input: 100–240 VAC, 50–60 Hz

## Use cases

- Industrial automation serial-device networking over Wi-Fi
- Power and energy serial-device data connectivity
- Rail transit and public-facility serial communications
- Building automation and control with serial equipment
- Modbus RTU equipment integration with Modbus TCP over Wi-Fi

## FAQ

### Which serial interface does the PW31-AC provide?
It provides one RS485 interface. Connect A+ to A+ and B− to B− using a twisted pair; a shared GND is recommended under interference.
### Which power supply does this variant require?
The PW31-AC accepts 100–240 VAC, 50–60 Hz. Power input uses L and N terminals.
### Which Wi-Fi modes are supported?
IEEE 802.11 a/b/g/n operates in the 2.4 GHz and 5 GHz bands with STA, AP, or AP+STA modes. AP+STA does not provide Wi-Fi relay; AP and STA must use different IP subnets.
### Does it convert Modbus RTU and Modbus TCP?
Yes. The manual specifies bidirectional Modbus TCP ↔ Modbus RTU conversion, timed acquisition, and data format conversion.
### Which serial settings are listed in the manual?
7/8 data bits, 1/2 stop bits, None/Even/Odd parity, and software Xon/Xoff. The baud-rate row lists 300–230400 bps but is labeled “TTL”; applicability to the external serial interface requires confirmation.
### How is it configured, updated, and reset?
Use the Web interface, serial CLI, XML import, Telnet, companion configuration software, or app-based Wi-Fi provisioning. Wireless OTA updates use the Web interface or companion software. Hold Reload for more than 4 seconds and release to restore defaults; Reset performs a hardware reset.

## Related

- [Wi-Fi](https://www.iiotsys.net/technologies/wi-fi)
- [RS-485/RS-232](https://www.iiotsys.net/technologies/rs-485rs-232)
- [Modbus RTU/TCP](https://www.iiotsys.net/technologies/modbus-rtutcp)
- [MQTT](https://www.iiotsys.net/technologies/mqtt)
- [DIN Rail Mount](https://www.iiotsys.net/technologies/din-rail-mount)