Wiznet makers

📌 The EUR 24.90 Kit Contains No Ethernet Part

Horter & Kalb, an electronics maker in Bayreuth, Bavaria, sells solder kits for the I2C bus and converters for SIMATIC S5 controllers. Its article 292, reference I2ARL-Bk, is an "I2C master kit with ARDUINO-UNO and optional W5500 LAN on DIN rail", and optional is the word that decides this build. For EUR 24.90 the bag holds an ATmega328P, a 16 MHz crystal, a 7405 inverter, an LM1117-3.3 regulator, four LEDs and three 1x6 sockets, and no Ethernet part.

Everything article 292 contains for EUR 24.90. No Ethernet part is in this photograph. Product photo: Horter & Kalb, horter-shop.de.

Ethernet is article 293, a EUR 11.90 module listed in the Accessories block as "W5500 TCP/IP Ethernet module for I2C master I2ARL", which the vendor calls "a powerful Ethernet controller with an integrated TCP/IP stack". Buying both is what turns the kit into a networked device, since the ATmega328P has no Ethernet MAC of its own.

Vendor, Availability, and Price

Horter & Kalb sells directly from its own PrestaShop store at horter-shop.de, with no distributor in between. The GPSR notice and shop footer name Juergen Horter, Klinikumallee 23, 95445 Bayreuth, mail@horter.de, as the person responsible for the EU. The blog Impressum adds the phone +49 921 68374, VAT identification number DE250411431 and the title Industriemeister MSR from IHK Bayreuth.

Prices come from the product pages on 27 August 2026, both marked "Tax included" and "Shipping excluded". German shipping starts at EUR 2.50 for a letter under 15 grams and EUR 6.00 for a tracked DHL parcel, EU deliveries at EUR 17.50.

The kit page declares schema.org InStock and Add to cart is active, but the PrestaShop record reports -7 units for the fixed-terminal option and -11 across all options with out-of-stock ordering permitted, so an order today is a back order. The module sits at 970. Article 292 was created on 29 May 2020 and last edited on 2 November 2025, a long-standing catalogue item rather than a 2026 release.

What the Board Offers Before the LAN Option Arrives

The I2ARL is an Arduino UNO built onto a DIN-rail-shaped PCB, not a carrier for a separate Arduino, and the product page states that "The Arduino bootloader and a small demo program are pre-installed on the ATMEGA328P." Screw terminals bring out +5V, GND, SDA, SCL and INT, three LEDs show bus activity, and two white connectors chain further Horter cards.

The same board fully soldered but without the LAN option. The three empty six-pin sockets are the whole Ethernet story. Product photo: Horter & Kalb, horter-shop.de.

The parts list calls the three strips "socket strip 1x6pol für LAN / USB", quantity 3. Two are the LAN sockets J1 and J2, the third is for programming, and the only networking entry under the data sheet's Option heading is "U1 W5500 Ethernet-Netzwerkmodul", quantity 1.

⚙️ Role of the W5500: Five Nets Between the Module and the MCU

The ATmega328P has no Ethernet MAC and no PHY, and the company blog gives its budget as 32 KB flash and 2 KB SRAM, too little for a software TCP/IP stack and its buffers. The W5500 carries that stack in silicon, which is why article 292 lists a "- Slot for WizNET W5500 LAN module" and why the German family overview ties that slot to "Modbus TCP oder MQTT-Netzwerkanwendungen", Modbus TCP or MQTT network applications.

The module Horter & Kalb sells for that slot is a W5500 Lite board with a HanRun HR961160C magnetic RJ45 jack, date code 2232. Its underside shows an LQFP-48 package whose first marking line reads W5500 beside the crystal can that clocks it, though the vendor photograph does not resolve that can's marking. Silkscreen reads W5500 and Lite, with indicator openings labelled Link and Active.

The package marking on the module Horter & Kalb sells as article 293. Product photo: Horter & Kalb, horter-shop.de, cropped and enlarged.

The schematic sheet of 6 January 2025 draws the LAN slot as one block of two six-pin connectors: five signals cross to the microcontroller, plus power and ground.

Two module pins carry no net at all: /INT on J1.6 goes nowhere, so the firmware polls the W5500 instead of waking on it, and PWDN on J2.4 goes nowhere either, so the chip stays awake whenever the board has power.

Generated technical diagram, drawn for this article from the I2ARL schematic sheet and the module silkscreen.

From Four I2C Cards to a Siemens S7-1511

Horter & Kalb published a worked example on 17 January 2025, revised 8 January 2026. Its head, in the author's words, is "der Arduino-I2C-Master mit gestecktem WizNET W5500 LAN-Modul", the master with the module fitted, and four Horter cards share the rail below, digital input at I2C address 112, digital output at 64, analog input at 16 and analog output at 176.

The example system: the I2ARL with the W5500 fitted at the left, then digital in, digital out, analog in and analog out cards on the same I2C bus. Image: Horter & Kalb, horter.de blog.

The sketch uses the modbus-arduino library by Andre Sarmento Barbosa, BSD-3-Clause, with 483 stars and 268 forks on 27 August 2026. It declares a ModbusIP mb; object, calls mb.config(mac, ip) for 192.168.1.7 and registers six input and five holding registers, reaching the PLC as 30001 to 30006 inbound and 40001 to 40005 outbound.

libraries/ModbusIP/ModbusIP.h includes <SPI.h> and <Ethernet.h> and holds an EthernetServer, and the README states that the standard Arduino Ethernet shield "is based on chip WIZnet W5100", with a separate ModbusIP_ENC28J60 library for the Microchip part. Every Modbus frame on the I2ARL is therefore assembled by the W5500 socket engine, not by software on the AVR.

This fragment, printed under the product page's "program examples" tab, ties the blue front-panel LED to the same chip:

bool takt_1hz = (millis() / 500) & 1;      // Blinktakt 1 Hz
auto link = Ethernet.linkStatus();
switch (link) {
  case Unknown: digitalWrite(LED_BL, takt_1hz); break;
  case LinkON:  digitalWrite(LED_BL, HIGH);     break;
  case LinkOFF: digitalWrite(LED_BL, LOW);      break;
}

In the Arduino Ethernet library, linkStatus() reaches W5100Class::getLinkStatus(), which returns LinkON or LinkOFF only for chip identifier 52, the W5200, and 55, the W5500, reading PHYCFGR at 0x002E; every other part including the older W5100 falls through to Unknown. A solid blue LED on digital pin 8, PB0, means the ATmega328P read the W5500 PHY register.

The author names his bench: "Als SPS habe ich eine SIEMENS SIMATIC S7-1511 CPU auf meinem Teststand", a SIMATIC S7-1511 on his own test rig. TIA Portal uses MB_CLIENT with two TCON_IP_V4 structures, connection type 11 and remote port 502, downloadable as a TIA V17 library whose counter read 1799 on 27 August 2026.

Where the I2ARL Sits in the Horter I2C Master Line

Category 120 listed 14 items on 27 August 2026, six of them master kits. In the blog family table the I2ARL row reads "LAN-Option" and "WizNET W5500" for the network and "SPS-Modbus, Hutschiene" for its use, PLC Modbus on the DIN rail.

Two of the six kits reach a wired network by different routes, and the W5500 is not the vendor's only path to Ethernet. The I2NOL hosts a WT32-ETH01 board, a "Steckplatz für NodeMCU ESP32-ETH01 (ESP32 Dual-Core + LAN8720 Ethernet)" whose LAN line reads "LAN8720, RJ45, 10/100 MBit/s". A LAN8720 is a physical-layer transceiver, not a protocol stack, so TCP/IP there falls to software on the ESP32. The I2ARL is the only kit whose host processor cannot carry that load, and the only one where a WIZnet part supplies the network layer.

Generated illustration, built for this article from the shop category page and the family overview article. Product photographs: Horter & Kalb, horter-shop.de.

Getting It Onto the Rail and Loading a Sketch

The board is not a snap-on housing, so it reaches the rail on carrier I2HR at EUR 3.90, a "Set WAGO Mounting base for our I2C rails kits" marked WAGO 288, and its five-pole terminal takes 5 V from the I2HN3-Bk supply kit at EUR 12.90. Firmware arrives over the third socket through the CP2102 adapter sold as M-USB_TTL for EUR 6.95, which the product page insists on: "Please order the programming adapter separately!"

The complete assembly: I2ARL on a WAGO 288 carrier, W5500 module fitted, CP2102 adapter seated in the third socket. Product photo: Horter & Kalb, horter-shop.de.

What Is Published and What Is Not

Four public documents cover this kit: the data sheet PDF of 10 January 2025 with the parts list, the schematic PDF with the LAN slot wiring, the product page printing the whole sketch, and the blog article with the PLC side.

Several things are not published. No throughput or latency figures exist, so this article makes no performance claim about the W5500 on a 16 MHz AVR. No CE, RoHS or other conformity document appears on the page or the data sheet, and none is claimed here. The page carried no reviews on 27 August 2026, only the prompt "Be the first to write your review".

Independent evidence needs the same care. The German blog nikolaus-lueneburg.de has eight posts tagged Horter between 2016 and 17 February 2020 showing Horter I2C cards in real workshop and garden distribution boards. None mentions the I2ARL or a W5500, and the newest predates the I2ARL shop record of 29 May 2020, so use of this kit is not in the public record.

The I2ARL is a kit rather than an appliance: a buyer solders two DIP sockets, a regulator, four LEDs, three socket strips and a screw terminal before anything runs, and 2 KB of SRAM caps what a sketch can hold.

Related WIZnet Maker Projects

Guide to Modbus TCP ESP32 Communication between W5500 Module and Siemens S7 1200 PLC reaches the same destination from a much larger processor, a W5500 serving Modbus TCP registers to a SIMATIC controller.

How Does Weidmuller Weidos Use W5500 Ethernet for Open-Source Industrial IoT? is the same country and the same cabinet from the other end of the market, a finished enclosed controller.

OpenKNX REG1: A Bus-Powered DIN-Rail KNX-IP Router on RP2040 and W5500 repeats the plug-in pattern in building automation, a base board made networked by a small W5500 on SPI.

Arduino + W5500 Ethernet Series Overview (C & Modbus TCP) teaches the software route this kit depends on, ending at Modbus TCP with the Arduino Ethernet library the Horter sketch calls.

❓ FAQ

Q. Does the Horter I2ARL kit include a WIZnet W5500? No. Article 292 at EUR 24.90 has two empty 1x6 sockets for it, and the W5500 module is article 293 at EUR 11.90, so a working Ethernet build costs EUR 36.80 including German VAT, shipping extra.

Q. How is the W5500 module wired to the ATmega328P? Over SPI, on five nets: SCLK, MOSI, MISO and chip select reach ATmega328P pins 19, 17, 18 and 16, reset reaches pin 15, all of them port B bits, and 3.3 V comes from the on-board LM1117-3.3. Interrupt and power-down stay unconnected.

Q. What can the I2ARL do once the W5500 is fitted? The vendor lists two applications and publishes a sketch for the first, a Modbus TCP server exposing Horter digital and analog I2C cards as PLC registers 30001 to 30006 and 40001 to 40005, plus an MQTT gateway.

Q. Can I buy it today, and how long does delivery take? Add to cart is active for both articles on 27 August 2026, but the kit record shows negative internal stock with out-of-stock ordering allowed, so treat it as a back order. The shop states "Delivery time 3-5 working days germany / about 10 days Europe".

Q. Do I need anything else to program it? Yes, a serial adapter. The board has no USB port, so the third 1x6 socket takes the CP2102 micro USB to TTL UART adapter sold as M-USB_TTL for EUR 6.95.