Installing Siemens PC Adapter USB A2 Driver on Windows 10 64-bit

Overview

The Siemens PC Adapter USB A2 (order number 6GK1 571-0BA00-00A0) is a USB-to-MPI/PROFIBUS programming adapter used to connect a programming device to S7-300, S7-400, and C7 automation systems. On Windows 10 64-bit hosts running STEP 7 V5.7 (SIMATIC Manager), the adapter sometimes fails to enumerate or load its driver automatically. Windows lists the device with a yellow warning triangle under Universal Serial Bus controllers, or shows it as an Unknown device under Other devices. The adapter is electrically functional, but the host has not bound a driver to the USB endpoint.

This reference documents the manual driver update path that resolves the problem by pointing Device Manager directly at the driver package shipped inside the STEP 7 V5.7 installation tree. The procedure is endorsed in the Siemens support FAQ "How do you update the driver software for the PC Adapter USB if you cannot establish an online connection after installing STEP 7 (TIA Portal)?" and is valid on STEP 7 Classic V5.7 without TIA Portal being present on the host.

Affected Hardware and Software Matrix

Root Cause Analysis

Windows 10 64-bit introduced a stricter driver signing, store, and matching policy than Windows 7. When the PC Adapter USB A2 is plugged in for the first time after STEP 7 V5.7 is installed, two distinct failure modes are commonly observed:

1. Registry-side: STEP 7 V5.7's Set PG/PC Interface tool does not register the adapter entry under HKLM\SOFTWARE\Siemens\SINEC\LogDevices on a 64-bit host in a way that Windows PnP can resolve.
2. File-side: The driver INF inside STEP 7 is not copied into the system store at C:\Windows\INF by the installer, so the Windows generic Search automatically for updated driver software wizard returns no match and surfaces a yellow-triangle PC Adapter USB A2 entry in Device Manager.

Either condition prevents the host from binding a driver. The adapter is electrically present, but the bus binding step is not completed. The Siemens support FAQ referenced in the field report documents this exact root cause and the same resolution. The same fix applies on systems where only STEP 7 V5.7 Classic is installed and TIA Portal is absent.

Prerequisites

• Local administrator account on the Windows 10 64-bit host.
• STEP 7 V5.7 (or V5.6 / V5.5) installed and licensed; installation media or source folder must be reachable on a local or mapped network path.
• Siemens PC Adapter USB A2 with the original Siemens USB-A to USB-A cable (typically 5 m).
• Target S7 CPU powered and physically wired to the adapter via MPI or PROFIBUS.
• If the host enforces Secure Boot and the Siemens driver signature is rejected with Windows Code 52, the user must either disable driver signature enforcement temporarily or boot into Advanced Boot Options → Disable Driver Signature Enforcement for the install step.

Manual Driver Installation Procedure

1. Plug the PC Adapter USB A2 directly into a USB 2.0 or USB 3.0 port on the host. Avoid hubs and docks for the first enumeration. The USB indicator on the adapter housing should illuminate within approximately 2 seconds.
2. Open Device Manager (right-click Start → Device Manager). Expand Universal Serial Bus controllers and Other devices.
3. Locate the entry labelled PC Adapter USB A2 with a yellow warning triangle, or Unknown device.
4. Right-click the entry and select Update driver.
5. Choose Browse my computer for driver software → Let me pick from a list of device drivers on my computer.
6. Click Show All Devices, then Next.
7. Click Have Disk and browse to the STEP 7 driver folder. Typical paths on a 64-bit STEP 7 V5.7 install include:

   C:\Program Files (x86)\Siemens\Automation\Simatic Manager\Drivers\pc_adapter_usb
   C:\Program Files (x86)\Siemens\Automation\Simatic Manager\S7drivers
   C:\Program Files (x86)\Siemens\Automation\Simatic Manager\pg_pcabin

   The exact subfolder containing sipluspcadapterusb.inf, pcadapterusb.inf, or the legacy siplus7.inf is the directory to select.
8. Click OK, then Next. Windows will surface a Windows Security prompt about the publisher; choose Install this driver software anyway.
9. Wait for the file copy and install to complete. The Device Manager entry should clear the yellow triangle within a few seconds.
10. Close Device Manager and proceed to PG/PC interface configuration.

dir /s /b "C:\Program Files (x86)\Siemens" *.inf | findstr /i "adapter"

Get-ChildItem -Path 'C:\Program Files (x86)\Siemens' -Recurse -Filter *.inf | Where-Object { $_.Name -match 'adapter' }

Configuring the PG/PC Interface in SIMATIC Manager

With the driver bound, the adapter must be registered with SIMATIC Manager's PG/PC interface set:

1. Open SIMATIC Manager → Options → Set PG/PC Interface.
2. From the Interface Parameter Assignment Used list, select one of:

   PC Adapter (MPI)
   PC Adapter (PROFIBUS)
   PC Adapter (Auto)

   PC Adapter (Auto) negotiates the bus type from the target and is suitable for a first online test against an unknown CPU.
3. Click Properties. On the PC Adapter tab, set the transmission rate and bus profile. For S7-300 MPI default, 187.5 kbps; for S7-400 MPI, 187.5 kbps; for PROFIBUS DP, 1.5 Mbps is a common commissioning starting point.
4. On the Local Connection tab, confirm the COM port assigned by Windows. Typical assignment is COM3 – COM8; the port is created by the Siemens USB-PPI bridge driver.
5. Click OK to commit the dialog and OK again to close the PG/PC interface dialog.

Verification Procedure

1. Open SIMATIC Manager and load the S7 project matching the target CPU. If no project is available, create a blank project.
2. Right-click the project node and select Accessible Nodes. SIMATIC Manager broadcasts a single MPI/PROFIBUS address and reports the CPU type, firmware version, module order number, and rack/slot layout.
3. Open HW Config and click Online → Download to Target System to confirm full read/write access. A successful download is the primary verification gate.
4. Re-open Device Manager and confirm that the PC Adapter USB A2 entry is no longer flagged and the driver version string matches the STEP 7 V5.7 release date.
5. From a command prompt, confirm the virtual COM port is present:

   mode | findstr /i "COM[0-9]"

   The PC Adapter USB A2 should appear with a stable COM number.

Common Error Conditions and Workarounds

LED Status and Hardware Diagnostics

The PC Adapter USB A2 housing provides status indication via LEDs on the upper face of the adapter body. Reference the Siemens PC Adapter USB A2 Operating Instructions for the exact LED map shipped with the unit. As a general diagnostic rule, the following states indicate the bus binding:

If the USB LED remains dark after plug-in, the issue is electrical (cable, port power) rather than driver-side. If the USB LED is on steady but the Active LED never flashes during an Accessible Nodes request, the issue is the bus profile, baud rate, or physical layer — not the driver.

Bus Profile Selection: MPI vs PROFIBUS

The PC Adapter USB A2 supports two logical bus types selectable in the PG/PC interface:

For a known S7-300 CPU, the MPI profile at 187.5 kbps is the correct starting point. PROFIBUS at 1.5 Mbps is the standard commissioning rate for DP networks, but baud rates up to 12 Mbps are supported by the adapter. Note that the PC Adapter USB A2 does not include bus termination; the network must be terminated at its physical ends only, never at the adapter's drop.

Compatibility Considerations and Field Tips

The PC Adapter USB A2 is the recommended programming path for S7-300, S7-400, and C7 systems. For S7-1200 and S7-1500 controllers, the adapter is not the preferred path — use the Siemens Ethernet CP or a TIA Portal-compatible Ethernet cable instead. The PC Adapter USB A2 does not support PROFINET.

When commissioning a panel that already has a TIA Portal STEP 7 install alongside the classic V5.7, the TIA driver takes precedence in the Windows driver store. In that case, the manual driver update path must point at the TIA S7drivers folder, not the SIMATIC Manager tree. The two install locations can be confirmed by searching for pcadapterusb.inf on the entire system drive.

On hosts with virtualisation layers (Hyper-V, VMware, VirtualBox), the USB passthrough for the PC Adapter must be exclusive to one guest. The adapter is not designed to be shared between multiple virtual machines simultaneously. Direct passthrough of the USB device is preferred over a virtual USB hub.

Troubleshooting Flow

Field Tips and Best Practices

• Always install the latest STEP 7 V5.7 hotfix before commissioning. The hotfix refines the driver copy step on Windows 10 64-bit and reduces the chance of a manual driver update being required.
• Disable USB selective suspend in the host power plan; this prevents the adapter from being de-enumerated after idle periods during long commissioning sessions.
• Lock the COM port number to a stable value in Device Manager to avoid PG/PC interface dialogs pointing at a stale COM number after reboot.
• When the adapter must operate on a plant network with hazardous voltages, install a USB isolator between the host and the adapter. The adapter itself is not isolated.
• When commissioning a mixed STEP 7 V5.7 and TIA Portal environment, pick the INF from the same-generation install tree to avoid version mismatches in the device tree.
• Keep a copy of the driver INF folder on a portable drive for fast field recovery when the installer media is not available.

FAQ