Siemens TP170A PC Connection USB PC Adapter Compatibility

TP170A Communication Interfaces Overview

The SIMATIC TP170A is a 5.7-inch compact operator panel from the SIMATIC Panel 170 family, released in the early 2000s for S7-200/S7-300/S7-400 visualization. It was supplied in two variants: a monochrome STN-LCD version (MLFB 6AV6 545-0BA15-2AX0) and a color STN-LCD version (6AV6 545-0BB15-2AX0). The panel uses a resistive analog touch with a 320 x 240 pixel (QVGA) resolution and is configured with ProTool up to V6.0 SP3 or WinCC flexible 2004 SP1 and later, including WinCC flexible 2008 SP3 and the WinCC flexible Micro panels edition.

From a connectivity standpoint, the TP170A exposes a fixed set of physical interfaces. There is no USB port on the device itself. The rear connector block carries:

• RS-232 / PPI / MPI (9-pin Sub-D, male): a single serial port that is software-switchable between PPI master/slave, MPI slave, and a point-to-point (PtP) RS-232 protocol. Default baud is 19.2 kbit/s for PPI, 187.5 kbit/s for MPI. Maximum MPI address is 31 (default) or 126 depending on the S7 CPU type.
• PROFIBUS DP optional interface on the "DP" sub-variant (e.g. 6AV6 545-0BC15-2AX0), 9-pin Sub-D female, isolated, up to 12 Mbit/s.
• Power supply 24 V DC (operating range 20.4 V - 28.8 V), max 0.5 A.

This interface inventory is the reason a USB PC adapter cannot be a drop-in solution: the PC side of the USB PC Adapter is USB 1.1/2.0, while the TP170A only speaks RS-232, PPI, MPI, or PROFIBUS. The two signaling domains must be bridged by a converter that the panel's firmware can identify, and that converter list is closed.

Why the USB PC Adapter Does Not Work with TP170A

The Siemens USB PC Adapter (MLFB 6ES7 972-0CB20-0XA0) and the later USB PC Adapter A2 (6ES7 972-0CB35-0XA0) are USB-to-RS485 transceivers that emulate a Siemens COM port and present PPI/MPI/PROFIBUS to the panel side. The TP170A is not in the released device list for either adapter. Siemens published the binding device list in the support entry "USB PC adapter / USB PC adapter A2 - released HMI devices", and the TP170A is excluded.

There are two engineering reasons for the exclusion:

1. Boot-loader and PPI handshake mismatch. The TP170A boot loader expects the older ProTool/early-WinCC flexible handshake on its RS-232/PPI port. The USB PC Adapter A2 firmware uses an MPI-only download protocol that the TP170A bootloader does not answer to during the early project-transfer stage. The PC therefore times out with "Connection to device failed (0000/0000)" or "The selected interface does not support the device".
2. Bus termination and 5 V power on pin 6. Some TP170A revisions feed 5 V onto Sub-D pin 6 to detect a "programming" cable. The USB PC Adapter only supplies 5 V on its MPI/PROFIBUS side via the bus terminator that is integrated in its connector hood, not via the standard RS-232 lines. The TP170A therefore never asserts a cable-present condition and stays in RUN mode.

Official Siemens Compatibility List for USB PC Adapter (A2)

The compatibility matrix is published by Siemens under support entry ID 19109408. The following table summarizes the released HMI targets for project download and OS update via the USB PC Adapter and USB PC Adapter A2.

* TP 177B and OP 77B are not in the official Siemens release list; some users have transferred projects over MPI with the USB PC Adapter, but Siemens will not support the configuration. Treat the result as out-of-spec.

Alternative 1: RS-232 Null-Modem Cable (PPI Point-to-Point)

The simplest, lowest-cost, fully-supported path is a point-to-point RS-232 null-modem cable between the PC's 9-pin COM port and the TP170A's PPI/MPI Sub-D connector. WinCC flexible will treat the cable as a "PPI" connection in the Transfer settings.

Siemens documents two valid cable assemblies:

• Standard null-modem (full handshake): 2-3 crossed, 4-5 crossed, 6-20 crossed, 7-8 crossed. Shield on the connector shell. Use a 6ES7 901-1BF00-0XA0 cable or any commercial shielded null-modem with the same pinout.
• Siemens 9-pin "PPI programming" cable (6ES7 901-1BD00-0XA0): includes 5 V on pin 6 from the PC side, used by older ProTool configurations. Not strictly required for TP170A running WinCC flexible 2004 or later.

Pin map for a TP170A-compatible null-modem:

Configuration in WinCC flexible 2008 SP3:

1. Open the project, choose Project → Transfer → Transfer Settings.
2. Set Mode = "Serial (RS-232)" or "PPI".
3. Set Port = COM1 (or the virtual COM created by the USB-RS232 adapter).
4. Set Baud = 19200 bit/s for TP170A in PPI mode.
5. Click Transfer. The TP170A should display "Transfer in progress" on screen.

Alternative 2: CP5711 Communication Processor (MPI/DP over USB)

For engineers who need MPI or PROFIBUS at full 187.5 kbit/s - 12 Mbit/s and a true Siemens-supported path, the recommended hardware is the CP 5711 (MLFB 6GK1571-1AA00). The CP 5711 is a USB-attached communication processor that emulates a Siemens CP5611 over a high-speed USB bus. It supports:

• MPI master/slave, 187.5 kbit/s only (per CP 5711 firmware v1.x).
• PROFIBUS DP master Class 1 and Class 2, 9.6 kbit/s - 12 Mbit/s.
• S7 routing, PG functions, and HMI transfer (WinCC flexible, ProTool, STEP 7 V5.x).

CP 5711 driver stack on the PC side consists of the SIMATIC NET PC software, currently version V18 SP1 (or V13 SP2 for legacy WinCC flexible hosts). Install order: SIMATIC NET V18 → CP 5711 driver → restart → plug in CP 5711. The device appears in Device Manager under SIMATIC NET → CP 5711 and in PG/PC interface as CP5711(MPI) or CP5711(PROFIBUS).

CP 5711 - TP170A cabling:

• For MPI: use a standard MPI cable (6ES7 900-0AL00-0XA0) with a PROFIBUS DP connector at the panel end. The TP170A MPI port can be used; note that the panel is an MPI slave (address 1 default, range 1-126). The CP 5711 is the master.
• For PROFIBUS DP: same cable, set the CP 5711 in PG/PC interface to CP5711(PROFIBUS), configure a DP master at 1.5 Mbit/s (standard) and ensure the bus terminator is on at both ends.

Setting up the transfer in WinCC flexible 2008 SP3 with CP 5711:

1. Open Start → SIMATIC → PG/PC Interface.
2. Under Access Point select S7ONLINE.
3. Under Interface Parameterization Used choose CP5711(MPI) and click Properties. Set Address = 0, Transmission rate = 187.5 kbit/s, Highest MPI/PB address = 31.
4. Open the WinCC flexible project, Project → Transfer → Transfer Settings, set Mode = "MPI/PROFIBUS".
5. Set the panel MPI address (default 1) and click Transfer.

Alternative 3: Legacy CP Cards (CP5512, CP5611, CP5612)

Older PCI / PCMCIA communication processors remain fully supported and are the most stable option for shop-floor installations. These cards appear in the OS as real Siemens network adapters and avoid any USB-serial timing issues.

All five cards use the same S7ONLINE access point and appear in PG/PC interface. For WinCC flexible 2008 SP3, the SIMATIC NET version must be at least V8.2 + SP1; for TIA Portal V15.1 or later, SIMATIC NET V16 or newer is required. Mixing versions (e.g. SIMATIC NET V12 on a TIA V15 host) is the most common cause of "Interface not assigned" errors.

Configuring WinCC Flexible / TIA Portal for TP170A Transfer

WinCC flexible 2008 SP3 and TIA Portal both allow the TP170A to be configured as a target. The transfer pathway is identical from a hardware standpoint, but the access-point configuration differs.

WinCC flexible 2008 SP3 path:

1. Open the project, ensure the TP170A device is selected as the active target.
2. Open Project → Transfer → Transfer Settings.
3. Set Mode = MPI/PROFIBUS for CP5711 or CP5611, or Serial for the null-modem cable.
4. For the HMI Device Connection, set the panel address. TP170A default is 1.
5. Click Transfer. The HMI runtime switches to Transfer state and accepts the project.

TIA Portal V15.1 or V16 path (using TP170A as "Third-party" or migrating project):

1. Open the migrated TIA project (or import a WinCC flexible .hmi file).
2. Right-click the HMI device, select Download to device → Software (all).
3. Select the PG/PC interface as CP5711(MPI) or the appropriate COM port.
4. Click Load. TIA Portal will detect the TP170A via the standard Siemens transfer protocol.

PG/PC Interface Configuration in SIMATIC Manager

The PG/PC interface applet in SIMATIC Manager and WinCC flexible is the central routing point for the HMI transfer. The relevant access points are:

• S7ONLINE — used by STEP 7 V5.x and WinCC flexible for PG functions and HMI transfer over MPI/PROFIBUS.
• MODEM_PPI — used by PPI-only connections to S7-200 and OP 73 / TP 177 A.

For a CP 5711, the correct assignment is S7ONLINE → CP5711(MPI). For a USB-to-serial null-modem, use MODEM_PPI → PC/PPI cable (PPI) → COMx. Setting the wrong access point is the most common cause of transfer failure even when the cable is correct.

Driver Installation and Windows 10 Compatibility

Siemens officially supports SIMATIC NET V18 and CP 5711 driver 8.2.x on Windows 10 64-bit (build 1909 and later). STEP 7 V5.6 with WinCC flexible 2008 SP3 works on Windows 10 64-bit when the compatibility pack and the .NET 4.7.2 redistributable are installed. However, several known driver-layer pitfalls remain.

Symptom: "PC Adapter USB" does not appear in PG/PC interface. This is the issue described in the Siemens support thread "Can't find PC adapter USB when setting communication". The root cause is that the USB PC Adapter requires a separate driver package (S7USBCOUP) that is not installed with SIMATIC NET V18. Install it explicitly:

1. Insert the SIMATIC NET installation media. Navigate to \Disk1\Setup.exe.
2. Choose Custom installation and tick USB PC Adapter / USB PC Adapter A2.
3. Complete the install and reboot.
4. Plug the USB PC Adapter in. Windows 10 should auto-install the device as Siemens USB PC Adapter under Universal Serial Bus controllers.
5. Re-open PG/PC interface; the entry PC Adapter (USB) or PC Adapter (MPI) now appears.

Symptom: Device Manager shows "Code 10 - Device cannot start." Replace the USB cable. The USB PC Adapter is sensitive to cable length above 3 m; use the original Siemens 1.5 m cable only.

Commissioning and Verification Procedure

After installing the cable and the driver, verify the end-to-end path in this sequence. Do not skip steps; a transfer failure in step 4 with a green light in step 3 indicates a WinCC flexible configuration issue, not a hardware issue.

1. Power up the TP170A. Apply 24 V DC, observe the panel boot screen and the runtime view. Note the Transfer button under the panel's Service / Control Panel — it is hidden on production units; press and hold the upper-left corner of the touch during power-up to enter service.
2. Open PG/PC interface, select the CP5711 or COM port, and run Diagnostics → Test. A successful test shows OK and the bus scan lists the panel's MPI address (default 1).
3. Run Accessible Nodes in STEP 7 V5.x (or Online → Accessible devices in TIA Portal). The TP170A should appear with its MPI address and firmware version. Firmware 1.1.0 is the factory release; V1.1.4 is the latest and recommended.
4. In WinCC flexible 2008 SP3, choose Project → Transfer → Transfer. The status bar should read Transferring project to device … with a progress meter. A successful transfer ends with Transfer completed successfully and the panel reboots into the new runtime.
5. Verify touch calibration by tapping each of the four corners of the screen. The cursor must follow within 2 mm. If miscalibrated, re-enter service and run Calibrate touch.
6. Verify tag polling. Open Project → Tags → Start value test in WinCC flexible runtime simulation, change a value on the connected PLC, and confirm the value updates on the TP170A within 1 second at PPI or 250 ms at MPI.

Troubleshooting Matrix

Frequently Asked Questions