Siemens LOGO! 0BA7 Wi-Fi Network Access: Configuration Guide

1. Overview: Networking the LOGO! 0BA7 over WLAN

The Siemens LOGO! 0BA7 is the first hardware generation of the LOGO! 8 logic module family, released in 2014. It integrates a 10/100 Mbit Ethernet interface directly on the base module, a major step up from the LOGO! 6 (0BA6) generation that required the separate LOGO! CSM module for any Ethernet connectivity. The 0BA7 still has no integrated radio, so Wi-Fi access is achieved by placing the module on a wireless LAN through a router or access point. This is functionally identical to commissioning any industrial Ethernet node on a wireless network, but the 0BA7 introduces a constraint that trips up almost every first-time user: the module ships with DHCP enabled and a fallback address of 169.254.x.x, and any stable WLAN workflow must be anchored on a manually assigned IP, a properly configured DHCP reservation, or a fixed SSID-to-IP mapping on the router.

This reference covers the complete workflow for a LOGO! 0BA7 Wi-Fi link: hardware selection, first-time configuration over the wired Ethernet port (mandatory), access-point commissioning, IP assignment strategy, access protection with a program password, the built-in Web server, and LOGO! Soft Comfort programming across the wireless link. The article also documents the failure modes observed in field deployments, including the router configuration error reported in the original problem case, and provides a verification matrix for commissioning.

1.1 Hardware Identification

Confirm the module is actually a 0BA7 before applying any of the steps below. The order number on the front label carries the MLFB suffix:

Reference the Siemens LOGO! 0BA7 System Manual (10/2014) for the full pin-out and front-panel LED map.

1.2 Network Services Exposed by the 0BA7

2. Prerequisites

Before commissioning, confirm the following items are on hand. Missing any one of them is the most common cause of the original failure mode ("the LOGO! does not respond over Wi-Fi").

1. LOGO! Soft Comfort V8.0 or later, ideally V8.3.1 or newer for stable online behavior over wireless bridges. Available from the Siemens LOGO! Soft Comfort download page.
2. Ethernet patch cable (Cat 5e or better) for the initial wired connection. Wireless commissioning alone is not supported; the 0BA7 has no out-of-the-box wireless client mode.
3. WLAN router or access point with client mode or a dedicated Ethernet-to-Wi-Fi bridge. Common industrial choices include the SCALANCE W700 family (e.g., 6GK5722-1FC00-0AA0), Phoenix Contact FL WLAN 5100, or a consumer-grade unit set to client/bridge mode.
4. PC with wired Ethernet port for the first configuration pass. Disable any active Wi-Fi on the PC during the first commissioning to avoid asymmetric routing through two default gateways.
5. IP address plan for the LOGO!, the PC, and the router. A static assignment is recommended; the LOGO!'s DHCP client will work, but the wireless link adds latency and a short lease drop can disconnect an active Soft Comfort session.

3. Network Topology

The recommended topology keeps the LOGO! on a wired segment terminated at the wireless bridge, because a 0BA7 cannot join a WLAN as a station. The PC can attach to the LAN port of the same bridge (typical for industrial APs) or to the same SSID that the bridge is associated with (typical for consumer routers in client mode).

Three things must be true in this diagram for the LOGO! to be reachable wirelessly:

1. The bridge and the AP are on the same SSID and same L2 broadcast domain (no VLAN segmentation between the bridge's LAN and the AP's WLAN).
2. All three devices (LOGO!, bridge, PC) are in the same IP subnet unless the bridge performs NAT, in which case the PC must address the LOGO! through the bridge's WAN-side mapping.
3. No firewall on the AP, bridge, or PC blocks TCP/102 (S7), TCP/80 (Web), or the ICMP echo used for the "ping" reachability test.

4. First-Time Configuration over the Wired Ethernet Port

Wired configuration is non-negotiable. The LOGO! has no out-of-box wireless client mode, and even if it did, the wireless link cannot be the path of first reachability because the bridge itself must first be associated with the SSID it will be using, which requires configuration via its own wired management port.

4.1 Connect Directly to the LOGO!

1. Power the LOGO! base module (24 V DC for 12/24 RCE variants; 115/230 V AC for 230 RCE variants).
2. Connect the PC's Ethernet port to the LOGO!'s RJ-45 jack using a Cat 5e patch cable.
3. Set the PC's NIC to a static IP in 169.254.x.x or in the same subnet you intend for the LOGO! later (e.g., 192.168.0.1/24). Disable the PC's Wi-Fi adapter so the Soft Comfort traffic cannot leak to a default gateway.
4. Open a command prompt and ping the LOGO! at its default address. If the 0BA7 cannot obtain a DHCP lease, it falls back to a link-local address in 169.254.0.0/16. To find it on Windows: arp -a will list recent neighbors; on Linux use arp-scan -I eth0 169.254.0.0/16 or nmap -sn 169.254.0.0/24.

4.2 Set a Permanent IP on the 0BA7

Open LOGO! Soft Comfort, go to Tools → Transfer → Configure Network, and uncheck Obtain IP address automatically. Enter a static address such as 192.168.0.10 with mask 255.255.255.0 and gateway 192.168.0.1 (the WLAN bridge's LAN address). Click Apply to module. The module will accept the write only when the access protection level allows it (Section 6).

5. Configuring the WLAN Bridge and Access Point

This is the step that produced the original failure case. The router was misconfigured; the user expected a transparent bridge but the consumer unit was in router mode with NAT, firewall, and a default SSID on a different subnet than the wired LAN. Two paths solve it.

5.1 Industrial AP in Client Mode (SCALANCE W774-1)

1. Connect the SCALANCE's management port to the PC. Default address: 192.168.1.1 (set the PC to 192.168.1.2).
2. Open the Web-based management, set the device to Client mode rather than Access Point mode.
3. Enter the SSID of the plant network, security mode (WPA2-Enterprise with RADIUS or WPA2-PSK), and credentials.
4. Set the LAN-side address to 192.168.0.1/24 and disable the SCALANCE's DHCP server (the LOGO! is static).
5. Connect the LOGO! 0BA7's Ethernet port to one of the SCALANCE's LAN ports.
6. Verify: from the PC on the same SSID, ping 192.168.0.10 should return under 5 ms with no loss.

5.2 Consumer Router Reconfigured as a Bridge

Many consumer routers (TP-Link, Asus, Netgear) expose a Wireless Bridge or Access Point (AP) mode. AP mode is preferred over a generic bridge because the WAN-side NAT is disabled, so the wired and wireless clients share a single L3 network.

1. Reset the router to factory defaults.
2. Connect the PC to a LAN port, log in to the management page (usually 192.168.0.1 or 192.168.1.1).
3. Switch operation mode to Access Point. Disable DHCP server, set its IP to 192.168.0.1/24, and reserve a DHCP scope for clients only.
4. Set the SSID, channel, and security. Use WPA2-PSK (AES) at minimum; avoid WEP and TKIP-only modes.
5. Connect the LOGO! to a free LAN port of the AP.
6. From the wireless PC, ping 192.168.0.10.

6. Access Protection with a Program Password

The original poster asked whether IP changes can be password-protected "as with the password." Yes: the LOGO! 0BA7 supports an access protection scheme tied to the LOGO! Soft Comfort program. The protection is implemented at the project level, not at the IP level. Once a program on the 0BA7 carries a password, all online operations — read, write, run/stop, change operating mode, and change of network parameters via Tools → Transfer → Configure Network — require the operator to authenticate against the program password.

6.1 Setting the Program Password

1. In LOGO! Soft Comfort, open the program that is currently running on the module.
2. Go to File → Properties → Password Protection (or Tools → Options → Password depending on version).
3. Enter a password of 1 to 16 characters. The password is stored hashed in the program file and on the module's non-volatile memory.
4. Transfer the program to the module. The module reboots into run mode with protection active.

6.2 Effect on Online Operations

6.3 Password Recovery

There is no backdoor. If the program password is lost, the only recovery path is to factory-reset the module, which erases the Ladder program and returns all configuration to defaults. Back up the .lsc project file with its password metadata to a controlled directory.

7. Web Server and Monitoring over Wi-Fi

The 0BA7 ships with an on-board Web server. Activate it in Tools → Transfer → Configure Web Server (or via the on-device menu if your firmware exposes it). With the Web server enabled, browsing to http://192.168.0.10/ from the wireless PC yields the LOGO! home page; navigating to http://192.168.0.10/logo_basic.svg (firmware-dependent) or one of the predefined variable pages shows the live I/O state.

Authentication: the Web server uses HTTP Basic Auth by default with the operator-set user and password. Always replace the default credentials; the default is well known.

8. LOGO! Soft Comfort over the Wireless Link

Once the wired-first commissioning is complete and the wireless bridge is online, Soft Comfort sees the module exactly the same way it does on a wired network. The only changes are the access interface and the timeout values, which can be raised to ride out wireless jitter.

1. In LOGO! Soft Comfort, open the project. Go to Tools → Transfer → Options.
2. Set the target IP to 192.168.0.10 (or the static you assigned).
3. Increase the Timeout to 15000 ms (15 s) to tolerate RF retransmissions.
4. Click Online → Connect. The first connection may take 2–5 s longer than a wired session because of the wireless association handshake.
5. Verify the round-trip: Online → Read Program from LOGO! should return the program and pass a checksum compare.

8.1 Throughput Reference

Soft Comfort traffic on TCP/102 is bursty and small. A 50-block program uploads in well under one second on a clean wired link; over a healthy 5 GHz bridge, expect 0.5 to 2 s. A 2.4 GHz link with 30 % channel utilization can push this to 5–10 s, which is why the timeout should be raised as a preventive measure.

8.2 Bandwidth and Capacity Planning

The 0BA7 is not a high-bandwidth device, but the wireless link introduces shared-medium contention. A simple sizing rule for a plant Wi-Fi segment with N LOGO! modules all being monitored concurrently:

Aggregate Soft Comfort throughput ≈ N × 200 kbit/s (peak, including retries and TCP overhead). A single 802.11n AP on a clean channel carries ~80 Mbit/s of usable throughput in 2.4 GHz and ~250 Mbit/s in 5 GHz; this is rarely the constraint. The constraint is the AP's number of associated clients and the per-client contention window. A practical ceiling is 25 to 40 active LOGO! clients per AP, beyond which TCP retransmits on TCP/102 climb and online sessions degrade.

9. Verification Matrix

Run the following checks after every commissioning. Each is a single test that fails fast and points to a specific root cause if it does not return the expected result.

10. Troubleshooting Matrix

11. Field-Proven Caveats

Wired first, every time. Both the access point and the bridge must be commissioned via their wired management interfaces the first time. After the association is established, they will survive most power cycles, but a factory reset of either device wipes the configuration and you are back to the wired port.

Static IP on the LOGO! is the safest path. The 0BA7's DHCP client is robust on a wired LAN, but on a wireless bridge a lease drop can disconnect a live Soft Comfort session and leave the program in an undefined state during upload. Static IP eliminates the race.

Use the program password, not the Web server password, to gate IP changes. The Web server is read-only; it does not protect the writable control surface. The program password does both: it protects the Ladder program and the network configuration, because Tools → Transfer → Configure Network requires an online session, and online sessions require the program password.

Avoid double NAT. If the consumer router cannot be set to AP or bridge mode, replace it. Industrial deployments should use a dedicated AP such as the SCALANCE W774-1 (6GK5774-1FY00-0AA0) or W778-1; the ruggedized mechanical and electrical specifications are not negotiable on a shop floor.

Document the SSID, channel, and security mode. When the access point is replaced in a maintenance window, the bridge will not re-associate automatically. A documented SSID and PSK means the new AP is configured identically and the LOGO! comes back without a site visit.

12. Quick Reference Parameter Sheet

13. Related References

For deeper coverage of the LOGO! 8 networking model — including the S7 connection parameters used by Soft Comfort and the variable list exposed by the Web server — see the LOGO! 0BA7 System Manual available from the Siemens Industry Online Support portal and the LOGO! Soft Comfort V8.x product page. For the SCALANCE W700 client/AP modes, refer to the SCALANCE W700 configuration manual.