Resolving LOGO! USB Cable 6ED1057-1AA01-0BA0 Driver Issue on Win7

Problem Description

When connecting a Siemens LOGO! USB PC programming cable (catalog number 6ED1057-1AA01-0BA0) to a Windows 7 (32-bit) workstation for the first time, the operating system reports "Driver not found" or fails to enumerate the device in Device Manager. The cable cannot be selected inside LOGO! Soft Comfort, and the upload/download toolbar buttons remain disabled even though the target LOGO! is placed in STOP mode. The same cable may also fail to enumerate inside Windows XP service-pack-2 virtual machines running under VMware Workstation, where the host OS reports the device but the guest cannot claim it. Symptoms cluster into three observable fault families:

• USB enumeration failure on first insertion (yellow exclamation in Device Manager, error Code 28 or Code 31).
• LOGO! Soft Comfort upload/download commands permanently greyed out.
• Interface selection dialog shows no COM port corresponding to the cable.

All three symptoms share a small set of root causes that must be ruled out in sequence: missing or skipped driver installation, wrong plug-in order, demo-software restriction, USB host/guest arbitration, and password-protected program images.

Affected Hardware and Software

Cable and Interface Specifications

The cable carries no external power supply. The USB-to-serial bridge IC only becomes active when the LOGO! end is plugged into a powered LOGO! base module, which is why the install sequence is non-trivial.

Root Cause Analysis

The driver-not-found symptom has five independent contributing causes. Each must be ruled out before moving to the next:

1. Driver never installed. Windows Plug-and-Play cannot locate a driver for the USB device because the LOGO! Soft Comfort installer was skipped, cancelled, or installed the driver only for a specific COM port that is no longer assigned. This is the dominant cause in fresh-workstation cases.
2. Wrong installation sequence. The cable electronics are powered by the LOGO! device. If the cable is plugged into the PC USB port before it is plugged into the LOGO!, the device enumerates with default VID/PID values that Windows cannot match against the LOGO! driver INF file, and a generic USB device entry appears instead.
3. Unsigned or blocked driver on Windows 7. Windows 7 enforces driver signing. If the driver is unsigned, has been revoked, or was installed outside the LSC installer, Device Manager shows Code 52 ("Windows cannot verify the digital signature") and refuses to bind the driver.
4. LOGO! Soft Comfort running in DEMO mode. The DEMO edition disables the upload and download toolbar buttons regardless of cable state. The DEMO banner is visible in the title bar of LSC and in Help → About.
5. Virtual machine USB ownership. In a VMware Workstation guest, the Windows 7 host claims the USB device first; the guest cannot attach to it until the host releases the device or the VM explicitly captures it through the removable-devices menu.

Additional secondary causes that surface during commissioning:

• Cable inserted into a USB 3.0 port with an incompatible xHCI driver stack.
• Multiple stale COM port assignments from previous FTDI-family devices.
• LOGO! program protected by a user password; upload requires password entry before the toolbar is enabled.
• PLC in RUN mode; some LSC versions disable upload while the PLC is in RUN to protect the live program.

Correct Cable Installation Sequence

The 6ED1057-1AA01-0BA0 cable draws its operating power from the LOGO! base module through the proprietary device connector. The host-side USB connector alone does not power the bridge IC. This is the physical reason the install order matters. Follow this sequence exactly:

1. Plug the LOGO! end of the 6ED1057-1AA01-0BA0 into the LOGO! PLC communication port. The connector is keyed; do not force it.
2. Install or re-run the LOGO! Soft Comfort setup and select the option to install the USB driver. Do not skip the driver step when prompted.
3. Connect the USB Type-A end to the PC. Windows detects "LOGO! USB Cable" and assigns a virtual COM port (typically COM3, COM4, or higher depending on installed COM devices).

If the driver is installed in the wrong order, Windows binds the device to a generic USB device class and the cable never appears as a COM port. The corrective action is to uninstall the wrong driver binding in Device Manager, then reinsert the cable while LOGO! Soft Comfort is closed.

Step-by-Step Driver Installation on Windows 7 (32-bit)

1. Open Control Panel → Programs and Features and confirm a LOGO! Soft Comfort entry (V7.1.51 or later) is installed. If only a DEMO version is installed, the upload/download functions will remain locked regardless of driver state; obtain a licensed copy or a current V8.x release for LOGO! 8 hardware.
2. Close LOGO! Soft Comfort.
3. Insert the cable into the LOGO! PLC first; confirm the cable is fully seated. Power on the LOGO! if it is not already.
4. Insert the cable USB connector into the PC. Windows emits the "installing device driver software" notification.
5. If the "Device driver software was not successfully installed" balloon appears, choose Ask me again later and proceed manually.

a. Open Device Manager (devmgmt.msc).
b. Locate the new entry under Other devices → LOGO! USB Cable (yellow exclamation icon).
c. Right-click → Update Driver Software → Browse my computer for driver software.
d. Browse to C:\Program Files\Siemens\LOGO! Soft Comfort V7\Drivers or the equivalent Drivers subfolder under the LSC install path.
e. Select Include subfolders and click Next. Accept the Windows Security prompt if the driver is signed.

6. When installation completes, Device Manager should show the cable under Ports (COM & LPT) as "LOGO! USB Cable (COMx)" where x is the assigned COM port number. Note this number for the LOGO! Soft Comfort configuration step below.
7. If the entry appears under Universal Serial Bus controllers instead, the FTDI bridge driver was not loaded. Re-run the LSC installer and choose the Repair option.
8. Confirm the COM port is not conflicting with an existing COM device by inspecting the COM port properties → Advanced; if necessary, change the COM number to a free slot.

USB Enumeration and Driver Binding on Windows 7

USB enumeration follows a fixed sequence: host hub detects attach, device responds with descriptors (VID/PID/class), host searches for a matching driver INF, host loads the driver and assigns a device node. For the LOGO! USB cable:

• The cable exposes an FTDI-class VID/PID. Without the LOGO! Soft Comfort driver installed, Windows binds it to a generic USB device or to a previous driver from another FTDI tool (such as an Arduino IDE install).
• If a previous FTDI driver is bound, the cable appears under Universal Serial Bus controllers with a working entry but no COM port is created. Uninstall that binding and force re-enumeration.
• Driver pre-installation (adding the INF to the driver store before plugging the cable) avoids the "found new hardware" wizard and is the cleanest install path.

To force re-enumeration after uninstalling a stale driver, open an elevated command prompt and run:

set devmgr_show_nonpresent_devices=1
start devmgmt.msc

Then enable View → Show hidden devices, locate any greyed-out LOGO! USB Cable entries, right-click and Uninstall, then physically unplug and replug the cable.

Resolving "Upload Disabled" in LOGO! Soft Comfort

When the cable installs correctly but the upload button (PC ← LOGO!) and download button (PC → LOGO!) remain greyed out, work through this checklist in order:

1. Confirm licensed software. The Help → About dialog must NOT show "Demo" or "Trial". The DEMO edition blocks all upload, download, and online test functions. See the dedicated section below.
2. Confirm the LOGO! is in STOP mode. On the LOGO! display press ESC and confirm the cursor is not in RUN. Some LSC versions refuse to upload while the PLC is in RUN to protect the live program image.
3. Match the COM port. Open Tools → Options → Interface (or the equivalent Interface selection dialog reached from the toolbar). Select the COM port that Device Manager reports for the cable. If the list is empty, the cable is not enumerated; revisit the driver installation steps.
4. Refresh the interface list. After plugging or unplugging the cable, close and reopen LOGO! Soft Comfort; the COM port list is cached at startup.
5. Test online connection. Use Tools → PC ↔ LOGO! Connection Test (or click the online icon). A successful test displays the LOGO! firmware version and IP/COM identifier.
6. Use the keyboard shortcut to detect the PLC. Press Ctrl + H (or the equivalent PC ↔ LOGO! menu entry) to force the software to scan attached interfaces and identify the connected LOGO!.

If the connection test fails with "Interface not responding", the cable is enumerated but not communicating with the PLC; reseat the cable at both ends and confirm the LOGO! is powered.

LOGO! Soft Comfort DEMO Mode Restrictions

The DEMO version of LOGO! Soft Comfort is a fully featured program editor for offline use, but explicitly disables the following functions. This is the single most common reason a working cable appears "non-functional" in field reports:

Confirm the license in Help → About before pursuing hardware diagnostics. A demo version installed side-by-side with a licensed version does not automatically upgrade; the licensed version must be installed separately and registered.

Virtual Machine USB Passthrough on VMware Workstation

Running LOGO! Soft Comfort inside a Windows XP SP2 virtual machine under VMware Workstation introduces two extra failure modes that the native host environment does not exhibit:

1. Host claim of the USB device. Windows 7 host may bind the cable to its own driver stack before the guest can claim it. In VMware Workstation, click VM → Removable Devices → LOGO! USB Cable → Connect (Disconnect from Host). The cable LED should momentarily flicker as the guest re-enumerates the device.
2. USB arbitration timing. Some Workstation builds do not release the device promptly. The workaround is to stop the VMware USB Arbitration Service temporarily, plug the cable into the host, then start the service and re-attach the cable to the guest. Confirm the service is set to Automatic startup so it survives a reboot.

For LSC development on Windows XP guests, prefer running the software natively on a Windows 7 host. Virtualization introduces COM port timing variations that can cause sporadic upload timeouts on long program transfers, especially with programs over 200 function blocks.

Password-Protected Programs

LOGO! Soft Comfort V7 supports a user password on each circuit program. When a program is password-protected, the upload function requires the password before the toolbar button activates. If the password is lost:

• The program cannot be retrieved by software means.
• The only path is to download a known-good program over the password-protected image; the password requirement clears for subsequent uploads of the new program.
• Program documentation stored as PDF (a feature of LSC) does not contain the executable image and is not affected.

Plan password custody as part of program management. Many sites store the password in a controlled vault separate from the program backup files.

Troubleshooting Matrix

Verification Procedure

1. In Device Manager, the cable appears under Ports (COM & LPT) with no warning icon, and the assigned COM port is recorded.
2. LOGO! Soft Comfort opens without a "DEMO" or "Trial" indicator in the title bar or Help → About.
3. Tools → PC ↔ LOGO! → Connection Test completes and returns the LOGO! firmware version and order number.
4. The download (PC → LOGO!) and upload (LOGO! → PC) buttons are enabled and a small test program round-trips successfully.
5. After unplug and replug, the cable re-enumerates within 5 seconds and the COM port assignment is consistent.
6. Cycle power on the LOGO! while the cable is connected and confirm communication recovers without a manual unplug/replug of the cable.

Preventive Recommendations

• Document the COM port assignment in machine documentation so that future software installs on the same workstation can replicate it.
• Use a dedicated USB port for the LOGO! cable on engineering workstations. Avoid USB hubs that toggle power during suspend events.
• Keep the LOGO! Soft Comfort installer package available locally; do not rely on driver download from the OEM site during commissioning in environments with restricted internet access.
• Store program backups separately from the LSC installation media to keep password-protected programs recoverable even if a workstation is rebuilt.
• For virtualized development environments, prefer Windows 7 host with native LSC over VMware guests; USB passthrough reliability is the limiting factor.

Frequently Asked Questions