What might cause LoggerNet to display a “PakBus Framing Error” message such as "PakBusPort","F","PakBus framing error","Invalid low level signature"?
The invalid low-level signature means that LoggerNet has received some data into its serial port that it is trying to interpret as a PakBus data packet, but the data appears to be corrupt, as proven by a signature check on the packet. (The signature of the data logger response fails to correspond with the message contents.)
There are several reasons why this may occur:
- The data logger program or its settings are configured to write data on the port on which an attempt to connect is being made.
- Corruption of the data occurs between the data logger and LoggerNet. This is more likely to occur over a non-PakBus-aware radio link, but it can happen with suspect serial interfaces.
- There is a mismatch in baud rates between the computer serial port and the data logger. This can cause the computer UART to clock in what appears to be garbage bytes (usually FF or 00 hex). Typically when this occurs, there are accompanying fault messages in the comms log for the serial port that report a serial framing error or, perhaps, a buffer overflow.
- The link, for various reasons, can drop sequences of characters from transmissions. This can happen if the CPU on the computer is so loaded that it has a hard time processing serial interrupts in a timely fashion. It can also happen in the case of poorly written USB drivers for the device.
- An attempt is made to communicate via the wrong COM port, and a device other than the data logger responds.