Serial port B problem.


I am using a Rabbit 3700 and Im working in a proyect that involves the serial ports B, C, D and E.

When i have the programming cable connected (when debugging) to the 3700, all ports works perfectly but when I disconnect the programming cable, only the serial port B is not working.

I am using the alt pins of the serial B with the following define to use the port D pins:


Is there another way to use the serial port B? or I need to set up something else besides the define Im using?


Serial Port B is not supported on the RCM3700.
You can find the information in the RCM3700 user’s manual.
4.2 Serial Communication
The RCM3700 board does not have any serial transceivers directly on the board. However,
a serial interface may be incorporated on the board the RCM3700 is mounted on. For
example, the Prototyping Board has RS-232, RS-485 and IrDA transceiver chips.
4.2.1 Serial Ports
There are five serial ports designated as Serial Ports A, C, D, E, and F. All five serial ports
can operate in an asynchronous mode up to the baud rate of the system clock divided by 8.
An asynchronous port can handle 7 or 8 data bits. A 9th bit address scheme, where an
additional bit is sent to mark the first byte of a message, is also supported.
Serial Port A is normally used as a programming port, but may be used either as an asynchronous
or as a clocked serial port once application development has been completed and
the RCM3700 is operating in the Run Mode.
Serial Ports C and D can also be operated in the clocked serial mode. In this mode, a clock
line synchronously clocks the data in or out. Either of the two communicating devices can
supply the clock.
Serial Ports E and F can also be configured as HDLC serial ports. The IrDA protocol is
also supported in SDLC format by these two ports.
Serial Port F shares its pins with Serial Ports C and D on header J1, as shown in Figure 7.
The selection of port(s) depends on your need for two clocked serial ports (Serial Ports C
and D) vs. a second HDLC serial port (Serial Port F).

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This is correct – I believe serial port B is dedicated to the serial flash on the RCM3700.

Make sure the ground connection for the device connected to serial port B is in place. If it’s connected to your PC it might be getting the ground from the programming cable. Once you disconnect the programming cable, if you only have Tx and Rx connected the serial port will stop working.