Connecting Wi-Fi to the Mercury 115F cash register: full instructions with photos and tips

Mercury 115F — one of the most popular fiscal cash registers for small businesses, but its setup is through Wi-Fi This often raises questions. Without a proper network connection, the cash register will not be able to send receipts to the OFD, synchronize data with 1C, or update firmware. In this article, we'll discuss all connection methods — from choosing a router to solving typical errors like “No connection with the OFD” or “Unable to connect to the network.”

Peculiarity Mercury 115F the fact that it only supports Wi-Fi through external adapter (For example, TL-WN725N or D-Link DWA-131). This means you won't be able to connect to a wireless network without additional equipment. We'll explain in detail which adapter to choose, how to set it up, and what to do if your cash register can't see the network.

The instructions are valid for firmware Mercury 115F versions 5.0.0.XX and newer. If you have older firmware, some menu items may differ—we'll warn you about this separately.

1. What equipment is needed to connect the Mercury 115F to Wi-Fi?

To enable the cash register to operate via a wireless network, you will need:

• 📡 Wi-Fi adapter with support 802.11n (recommended) TP-Link TL-WN725N or ASUS USB-N10 Nano). Important: the adapter must be compatible with Linux, since the cash register operates on its basis.
• 🔌 USB extension cable (optional). If the adapter interferes with the cashier's work, it can be moved outside the cabinet using an extension cord.
• 📶 Router with support 2.4 GHz (5 GHz is not supported!) It's best to use a separate network for the cash register to avoid connection issues.
• 🔧 Screwdriver to open the cash register cover (if the adapter will be connected inside the case).

Not all adapters are suitable for Mercury 115FFor example, chip-based models Realtek RTL8188EU often cause connection errors. We tested several options and compiled a compatibility table:

If you have already purchased an adapter and it is not from the list, check its chipset using the program USBDeview (for Windows). Enter the chip name in the forum search. Mercury — Users often share their compatibility experiences.

⚠️ Attention: Some routers with enabled WPA3 or 802.11r (Fast Roaming) may block the cash register's connection. Before setting up, disable these features in the router's admin panel.

2. Preparing the router to work with Mercury 115F

Before connecting the adapter to the cash register, you need to properly configure the router. Basic requirements:

• 🔒 Security type: only WPA2-PSK (AES). WPA3 And TKIP are not supported.
• 📶 Frequency: 2.4 GHzIf your router has dual-band mode, create a separate network for the cash register.
• 🆔 SSID: The network name must contain only Latin letters and numbers (no spaces or symbols).
• 🔄 Channel: It is better to choose a fixed one (for example, 6 or 11) to avoid automatic switching.

Instructions for setting up a router (using an example) TP-Link):

1. Open your router's admin panel (usually 192.168.0.1 or 192.168.1.1).
2. Go to Wireless → Wireless Settings.
3. Install:
   • Network Name (SSID): Merury_Cash (example)
   • Region: Russia
   • Channel: 6 (or another free one)
   • Channel width: 20 MHz

In the section Wireless security select:

• Version: WPA2-Personal
• Encryption: AES
• Password: at least 8 characters (Latin + numbers)
• Save the settings and reboot the router.

If you have a router of a different brand (Keenetic, ASUS, Zyxel), the path to the settings may vary. The main thing is to adhere to the specified security and frequency parameters.

📊 What router do you use for your cash register?
TP-Link
Keenetic
ASUS
D-Link
Another

3. Connecting the Wi-Fi adapter to the Mercury 115F

Once the router is configured, you can connect the adapter to the cash register. There are two placement options:

1. External connection — The adapter plugs into the USB port on the back of the register. This is ideal if the register is located in an accessible location.
2. Internal connection — The adapter connects to a USB port on a circuit board inside the case. This requires disassembling the cash register, but it protects the adapter from damage.

Step-by-step instructions for external connection:

1. Unplug the cash register from the power outlet.
2. Insert the Wi-Fi adapter into the USB port (usually located on the right side of the back panel).
3. If the adapter is large, use USB extension cable, so as not to block other ports.
4. Turn on the cash register and wait until it is fully loaded (the logo will appear on the screen) Mercury).

For internal connection:

Unplug the cash register | Unscrew the 4 screws on the back cover | Carefully remove the cover without touching the circuit boards | Connect the adapter to the internal USB port (usually white) | Close the cover and secure it with screws -->

Important: When connecting internally, the adapter must be compact (e.g. ASUS USB-N10 Nano), otherwise the lid will not close.

After connecting the adapter, the cash register should recognize it. To check this:

1. Press the button at the checkout MENU.
2. Go to Settings → Network settings → Wi-Fi.
3. If the adapter is detected, you will see the message Adapter: Connected.

⚠️ Attention: If the cash register does not detect the adapter, check:

• Is the adapter connected securely (try a different port).
• Is the adapter chipset compatible (see table above).
• Is the cash register firmware updated (minimum version - 5.0.0.18).

4. Setting up Wi-Fi on the Mercury 115F cash register

Now we move on to the main step—entering network parameters. To do this:

1. At the checkout, press MENU → Settings → Network settings → Wi-Fi.
2. Select an item Search for networksThe checkout will scan the airwaves and display available networks.
3. Find your network (eg. Merury_Cash) and press OK.
4. Enter your Wi-Fi password. Please note: the keypad at the checkout is case-sensitive!
5. Select security type: WPA2-PSK (If the router is configured correctly, this item will already be selected).
6. Save the settings and wait for the connection to complete. A message will appear on the screen. Connected or IP received.

If the network is not found:

• 🔍 Make sure your router is turned on and has a network connection within a 5-10 meter radius of the cash register.
• 📡 Check that the router is not in the "Secure Mode" mode. Hide SSID (if hidden, enter the network name manually).
• 🔄 Reboot your router and cash register.

After successful connection, we recommend checking the connection with the OFD:

1. Go to MENU → OFD → Connection Test.
2. If the message appears Connection with the OFD has been established, the setup was successful.

5. Typical mistakes and their solutions

When setting up Wi-Fi on Mercury 115F Users encounter several common issues. We've compiled them into a table with solutions:

Error	Cause	Solution
Failed to initialize adapter	Incompatible Wi-Fi adapter or missing drivers.	Check the adapter model (must be on the chip) Ralink RT5370). Update your cash register firmware to the latest version.
No connection with the OFD	Incorrect proxy settings. Blocking ports on the router.	Disable the proxy in the checkout settings. Open ports on your router TCP 7777 And UDP 7778.
Authentication failed	Incorrect password or security type.	Check the case of the characters in the password. Make sure your router is turned on WPA2-PSK (AES).
IP address not received	DHCP is disabled on the router or the number of connections is limited.	Enable DHCP on your router. Increase the IP address pool (for example, from 192.168.0.100–200 to 192.168.0.100–250).

If none of the solutions helped, try reset the cash register's network settings:

1. Go to MENU → Settings → Network Settings → Reset.
2. Confirm the reset (the cash register will reboot).
3. Repeat the Wi-Fi setup from scratch.

What should I do if my cash register keeps disconnecting from Wi-Fi?

If the cash register loses connection after 5-10 minutes of operation, the problem may be:

1. Saving router energy — Disable the "Wi-Fi Power Saving" option in your router settings.

2. Adapter overheating - Try using a USB extension cable for better cooling.

3. Interference on the channel - Change the Wi-Fi channel to 1, 6 or 11 manually.

4. Old drivers - update the cash register firmware to version 5.0.3.XX or newer.

6. Checking the connection speed and stability

To make sure Wi-Fi is working properly, run a test:

1. At the checkout, go to MENU → Settings → Network Settings → Status.
2. Check the parameters:
   • Wi-Fi status: should be Connected.
   • IP address: must start with 192.168. (or another range of your network).
   • Signal level: not lower 50%.

Conduct a connection test with the OFD (MENU → OFD → Connection Test).

If the signal level is weak (<30%):

• 📌 Move the router closer to the checkout (maximum distance is 10 meters without obstacles).
• 🔄 Change your Wi-Fi channel to a less busy one (use the app Wi-Fi Analyzer for analysis).
• 📡 Install repeater (signal repeater) between the router and the cash register.

To check the actual speed, you can send a test check:

1. Generate a check for any amount (for example, 100 ₽).
2. Click Pay and select the payment type Cash.
3. After printing the receipt, check whether it has appeared in your personal account at the OFD (usually within 1–2 minutes).

⚠️ Attention: If receipts aren't arriving at the fiscal data operator (OFD), but Wi-Fi is connected, the problem may be with the fiscal storage device settings. Check the menu OFD The correct server address and FN number are indicated.

7. Alternative ways to connect to the Internet

If you're having trouble setting up Wi-Fi, consider these alternatives:

• 🔌 Wired connection (Ethernet) — the most stable method. This requires an adapter. USB-to-Ethernet (For example, TP-Link UE300).
• 📱 USB modem (3G/4G) — Suitable for retail locations without wireless internet. A SIM card with a device plan is required.
• 🔄 Hotspot mode on a smartphone — temporary solution. Create a hotspot on your phone and connect the cash register to it.

How to connect a cash register via a USB modem:

1. Buy a 4G modem with support Linux (For example, Huawei E3372).
2. Insert a SIM card with a device tariff (unlimited traffic).
3. Connect the modem to the cash register's USB port.
4. In the checkout menu, select Settings → Network settings → 3G/4G.
5. Enter your carrier's APN (e.g. internet.beeline.ru for Beeline).
6. Save the settings and restart the cash register.

Advantages of a wired connection:

• ⚡ Stability - no connection breaks.
• 🛡️ Security — it’s more difficult to intercept data.
• 📶 Speed - higher than Wi-Fi.

8. Updating firmware to improve Wi-Fi performance

If your cash register's Wi-Fi connection is unstable, it may be due to outdated firmware. To update the firmware:

1. Download the latest firmware from official Mercury website (Support section).
2. Unzip the archive and copy the firmware file (usually with the extension .pkg) to a flash drive (FAT32).
3. Insert the flash drive into the cash register's USB port.
4. Go to MENU → Settings → Software Update.
5. Select the firmware file and confirm the update.
6. Wait for the reboot (do not turn off the cash register!).

After update:

• Check the firmware version in the menu MENU → Information → Software version.
• Please try setting up Wi-Fi again (the settings may reset).

If Wi-Fi stops working after an update:

• 🔄 Reset network settings (MENU → Settings → Network Settings → Reset).
• 🔧 Check the adapter's compatibility with the new firmware (information is available in the release notes on the website) Mercury).

⚠️ Attention: Don't update the firmware via Wi-Fi—use a wired connection or a flash drive. Disrupting the over-the-air update may result in cash register breakdown.

FAQ: Answers to Frequently Asked Questions

Is it possible to connect the Mercury 115F to Wi-Fi without an adapter?

No, Mercury 115F does not have a built-in Wi-Fi module. For wireless connection, an external USB adapter is required (for example, TP-Link TL-WN725N).

My cash register connects to Wi-Fi, but it's not sending receipts to the fiscal data operator. What should I do?

The problem may be:

• Incorrect OFD settings (check the server address in the menu) OFD).
• Blocking ports on the router (open TCP 7777 And UDP 7778).
• Problems with the OFD operator (call your OFD support).

Also check what's on the menu Network Settings → Proxy is worth the value No.

What password should I enter when connecting to Wi-Fi?

Your Wi-Fi network password (the same one you use to connect your phone or laptop). Please note:

• Case is important (Password ≠ password).
• Symbols are entered via the on-screen keyboard of the cash register (switching between registers is the button Shift).

Is it possible to use one router for the cash register and other devices?

Yes, but we recommend:

• Create for cash register separate network (guest or additional SSID).
• Disable features for this network WPA3, 802.11r And Band Steeling.
• Reserve an IP address for the cash register in the router's DHCP settings.

This will help avoid conflicts with other devices.

What should I do if the adapter gets hot and the cash register switches off?

Adapter overheating is a common problem. Solutions:

• Use USB extension cableto move the adapter outside the case.
• Replace the adapter with a model with a metal case (for example, ASUS USB-N13).
• Reduce the transmission power on your router (in Wi-Fi settings).
• Check if the adapter is covered by foreign objects (boxes, walls).