Overview
The Siemens SIMATIC TP177B is a 4–6 inch touch-panel HMI that supports project transfer through two physical interfaces: a 10/100 Mb PROFINET (Ethernet) port and a USB 1.1 Type-A host port. Although Ethernet is the preferred path for engineering with WinCC Flexible 2008 SP5 / TIA Portal, many legacy installations and field-service scenarios still require a USB Type-A to Type-A transfer cable to load or backup projects when no network drop is available.
The crucial hardware fact is that the TP177B's USB port is a USB host (Type-A socket) — not a USB device port. A passive A-to-A male cable will not enumerate; two USB hosts cannot negotiate a connection by themselves. The cable must contain active bridge electronics that present one side as a virtual USB device (or create an IP-over-USB tunnel), which is why the source community universally recommends a "master-to-master" or "LapLink-style" transfer cable rather than an off-the-shelf A-to-A jumper.
This reference consolidates Siemens' own FAQ 19142034 and 22407522, the TP177B operating instructions, and field-proven cable options into one commissioning-ready document.
Prerequisites
- TP177B unit powered from a 24 V DC supply (terminals 1L+, 2L+).
- Engineering PC running one of: WinCC Flexible 2008 SP5 or later, TIA Portal V13 SP1 + WinCC Comfort/Advanced, or STEP 7 V5.5 + WinCC Flexible 2008 (for the older integration).
- USB driver for the bridge cable installed on the PC (most cables ship a CD or use a Windows in-box driver for RNDIS / virtual Ethernet).
- Project file (*.hmi, *.flex, or *.ap* under TIA Portal) compiled for the target device type (TP177B mono PN or TP177B color PN).
- Administrative rights on the engineering PC during the first USB enumeration.
TP177B Interface Identification
Before ordering a cable, confirm the physical ports on the rear of the unit. The relevant TP177B variants are listed below.
| MLFB / Part Number | Display | USB Port (Type-A) | Ethernet (RJ45) | PROFINET |
|---|---|---|---|---|
| 6AV6647-0AA11-3AX0 | 4" mono | 1 × USB 1.1 host | Yes (PN) | Yes |
| 6AV6647-0AB11-3AX0 | 4" color | 1 × USB 1.1 host | Yes (PN) | Yes |
| 6AV6647-0AC11-3AX0 | 6" mono PN | 1 × USB 1.1 host | Yes (PN) | Yes |
| 6AV6647-0AD11-3AX0 | 6" color PN/DP | 1 × USB 1.1 host | Yes (PN) or MPI/DP variant | Yes (PN variant) |
The USB socket on every TP177B variant is a Type-A receptacle (the same physical shape as a USB stick port on a PC). The PC end of the cable is therefore a Type-A plug, giving you the A-to-A topology the source community describes.
Why a Standard USB A-to-A Cable Fails
USB is a strict host/device (master/slave) bus. The TP177B behaves as a host and your engineering PC also behaves as a host. Connect two hosts with a passive A-male to A-male cable and:
- Both sides attempt to source VBUS (5 V) at 500 mA and back-feed each other.
- No device descriptor is ever returned, so the hub driver reports "Unknown USB Device (Device Descriptor Request Failed)" in Windows.
- WinCC Flexible / TIA Portal will not see the panel during transfer.
An active USB transfer cable solves this by embedding a small controller (commonly a Prolific PL-25A1, OTI-9800, or the newer OTI-7300 bridge chip) plus a powered hub. One side enumerates as a USB device (Ethernet-over-USB / RNDIS / WinUSB) while the other side continues to look like a host. From the panel's perspective the cable looks like a USB-to-Ethernet adapter — and the panel's internal stack will treat the link as a TCP/IP interface.
Required Cable: USB Transfer / Bridge Cable
Siemens' official FAQ 19142034 and the related entry 22407522 list compatible USB transfer cables. The PDFs referenced by both entries are available in German (with English machine-translated mirrors on the same Siemens support page). Verified working options on TP177B hardware include:
| Cable / Model | Bridge Chip | Driver | Status on TP177B |
|---|---|---|---|
| LapLink USB Transfer Cable (PC-to-PC) | Prolific PL-25A1 | Windows in-box (RNDIS) | Field-confirmed working |
| Belkin F5U279 USB Transfer Cable | Prolific PL-25A1 | Prolific / Windows RNDIS | Confirmed in Siemens FAQ 19142034 |
| Hama 00039734 USB Data Link Cable | Prolific PL-25A1 | Prolific / RNDIS | Confirmed in Siemens FAQ 19142034 |
| Renkforce USB-Link-Kabel (Conrad 100080) | Prolific PL-25A1 | Prolific / RNDIS | Reported working |
| Plugable USB 2.0 Transfer Cable (USBC-MM) | OTI-7300 | Windows in-box (RNDIS/Ethernet) | Working on TP177B firmware ≥ 14 |
Pin / Connector Detail
Both ends are physically Type-A. The source question correctly rules out extension-cable geometry (plug-to-socket); the cable is plug-to-plug, but it is not a passive extension. The four active USB signal lines plus VBUS and GND are routed through the bridge PCB inside the molded hood at each end.
| Pin | Signal | Color (typical) |
|---|---|---|
| 1 | VBUS (+5 V) | Red |
| 2 | D− | White |
| 3 | D+ | Green |
| 4 | GND | Black |
| 5 | Shell / Shield | Bare / drain wire |
Within the bridge, VBUS is normally disabled on the host-emulating side to prevent back-power; the cable draws 5 V from whichever end is enumerated first.
Step-by-Step: Programming a TP177B over USB
- Install the bridge-cable driver on the engineering PC before plugging in. For Prolific PL-25A1 cables, run the bundled setup or let Windows Update fetch the RNDIS driver.
- Open the Control Panel > Network Connections on the PC. After plugging the cable, a new "USB Ethernet / RNDIS" adapter should appear. If multiple cables have been used, rename the adapter (e.g., TP177B USB) for clarity.
-
Assign a static IP to the new virtual adapter. The TP177B default USB-over-IP tunnel uses
192.168.1.1 / 24on the panel side; set the PC to192.168.1.100 / 24with no gateway. The TP177B's Ethernet and the USB virtual adapter share the same IP stack, so the static IP must not collide with the panel's PROFINET address. -
Verify the link:
ping 192.168.1.1from the PC. A reply confirms the bridge is up and the panel's IP stack is alive. - Open WinCC Flexible 2008 (or TIA Portal with the TP177B device package). Open the project, choose Project > Transfer > Transfer Settings.
-
Select the mode "Ethernet / USB (PN/IE)". Set the HMI IP to
192.168.1.1and the PC connection to the renamed USB adapter. - On the panel, enter the Transfer menu (touch the top-left corner during boot or use the loader menu) and enable Transfer via USB or Transfer via Ethernet. The panel will show "Connecting..." and start listening on port 5000 (HMI transfer) and 102 (S7ONLINE for TIA Portal).
- Start the transfer from the PC. Compilation > download typically takes 30–120 s for a 4 MB project on the USB 1.1 link.
- Reboot the panel when prompted. The new runtime will start and display the first configured screen.
WinCC Flexible / TIA Portal Configuration Parameters
| Parameter | Value (USB bridge mode) |
|---|---|
| HMI device | TP177B mono PN / TP177B color PN |
| Connection type | Ethernet / USB (PN/IE) |
| HMI IP address | 192.168.1.1 (default) |
| Subnet mask | 255.255.255.0 |
| PC interface parameter assignment | "Use TCP/IP from PC interface" |
| PC interface (PG/PC interface) | <Name of the USB bridge adapter>.TCPIP.1 |
| Access point | S7ONLINE (for TIA Portal) or HMI (for WinCC Flexible) |
| Port | 5000 (HMI) / 102 (S7ONLINE) |
Transfer Speed and Timing
USB 1.1 Full-Speed is the electrical ceiling on the TP177B side. Practical throughput over the bridge is 6–8 Mb/s real-world, which yields these typical transfer times:
| Project Size | Approx. Transfer Time (USB) | Approx. Transfer Time (10/100 Ethernet) |
|---|---|---|
| 1 MB (text + tags) | 3–5 s | < 1 s |
| 5 MB (typical) | 15–20 s | 1–2 s |
| 15 MB (with logs/graphics) | 45–60 s | 3–5 s |
| 30 MB (large image library) | 90–120 s | 5–8 s |
Reserve the USB path for troubleshooting, recovery after a corrupted image, or for sites where the network cannot be touched.
Verification
- After the transfer completes, the PC shows Transfer completed successfully in the dialog.
- The panel display leaves the "Connecting..." state and shows the configured start screen within 30 s of reboot.
- Touch the System > Information > Version screen and confirm the project CRC matches the PC-side compiled image.
- Disconnect the USB bridge and confirm the panel continues to run autonomously (the USB cable is only a transfer medium; runtime does not depend on it).
- On the PC, the Event Viewer > System should show a clean USB RNDIS disconnect with no error code 43 ("Unknown USB Device") or code 28 ("Drivers not installed").
Firmware and Image Considerations
The TP177B shipped with several image versions:
| Image Version | Behavior on USB transfer |
|---|---|
| V14.x (early, 2007–2009) | USB host stack older, sensitive to cable LED polarity. Some LapLink clones fail; genuine Belkin F5U279 recommended. |
| V15.x (2010–2013) | Improved RNDIS handling; most modern cables enumerate on first plug. |
| V16.x / V17.x (2014+) | Full plug-and-play with RNDIS-class bridges; OTI-7300 cables (e.g., Plugable USBC-MM with USB-A adapter) enumerate immediately. |
The image version is visible in the loader menu under System > About, or via the "bshwiz" / "rt_loader" splash string during boot. Update the panel image through the same USB transfer path before commissioning a new project if the source project was compiled against a newer runtime.
Troubleshooting Matrix
| Symptom | Likely Cause | Action |
|---|---|---|
| PC reports "Unknown USB Device (Device Descriptor Request Failed)" | Passive A-to-A cable or broken bridge electronics | Replace with active bridge cable from the verified list above. |
Adapter enumerates but ping 192.168.1.1 times out |
Static IP collision or panel set to PROFINET-only | Disable other network adapters, set static IP, enable USB transfer in panel loader. |
| WinCC reports "Connection to HMI failed (timeout)" | Access point mis-selected | Change PG/PC interface to <AdapterName>.TCPIP.1 and access point to S7ONLINE. |
| Driver installs but link drops after 30 s | USB selective suspend / power policy | In Windows Power Options > USB settings, disable selective suspend. |
| Transfer starts, then fails at 10–20 % | Cable length > 3 m or noisy industrial environment | Shorten cable, route away from VFD / welding cables, add ferrite clamp. |
| Panel shows "Boot error: 0x8003" | Corrupted image after failed transfer | Retry via USB from a freshly compiled project; do not power off during the next transfer. |
| Panel not detected in TIA Portal device discovery | Windows firewall blocking UDP/TCP 34964, 102, 5000 | Add firewall rules for the TIA Portal process or disable firewall on the isolated engineering network. |
Alternative: MPI / RS-232 Path
If no working USB bridge is available, the TP177B color DP variant (6AV6647-0AD11-3AX0) still supports a Siemens 6ES7 901-3DB30-0XA0 PC/PPI cable (USB-to-RS-232 adapter plus MPI) for transfer. WinCC Flexible still supports this legacy access point S7ONLINE > PC Adapter (PPI). Use this only as a last resort — its 187.5 kbps throughput makes a 15 MB project take 10+ minutes.
Frequently Asked Questions
What type of USB cable do I need to program a Siemens TP177B?
You need an active USB Type-A to Type-A transfer/bridge cable (also called a "master-to-master" or "LapLink" cable), such as the Belkin F5U279, Hama 00039734, or Renkforce 100080. A passive A-to-A jumper will not enumerate — refer to Siemens FAQ 19142034 for the verified list.
Is the TP177B's USB port a host or a device port?
The TP177B exposes a USB 1.1 Type-A host port intended for memory sticks, mice, and keyboards. To transfer a project from a PC, the PC also acts as a host, so an active bridge cable (with embedded electronics) is required to mediate the two hosts.
Can I use a regular USB A-to-A extension cable instead?
No. A passive plug-to-socket extension has no bridge controller; the panel will never see a device descriptor, and Windows will show "Unknown USB Device (Device Descriptor Request Failed)". Always use an active bridge cable from the Siemens-tested list.
Which IP address does the TP177B use for USB transfers?
The panel's default IP for the USB virtual Ethernet is 192.168.1.1 with subnet mask 255.255.255.0. Assign the PC a static IP in the same subnet, e.g., 192.168.1.100 / 24, and verify with ping 192.168.1.1 before launching WinCC Flexible / TIA Portal.
Where are the Siemens TP177B USB-cable FAQs located?
The two primary references are Siemens FAQ 19142034 and FAQ 22407522. Both are hosted on the official Siemens Industry Online Support portal. The PDF attachments are in German; the portal's automated English translation is available on the same pages.
Is it faster to use Ethernet instead of USB for TP177B transfer?
Yes — the TP177B's 10/100 Mb PROFINET port is roughly 10× faster in real-world transfer than a USB 1.1 bridge. Use Ethernet for projects above 5 MB; reserve USB for sites where no IP network is reachable or for recovery on a bench.