Port MuxR Adapter Design
The Port MuxR is quite extensible through the use of adapter boards. To aid the design of new adapter boards, we have created some EDA libraries in the Port MuxR hardware repository. These libraries provide the precise footprint and symbols you require to make new adapter board designs quickly and easily. The libraries provision the connector holes for the various ports, as well as additional connections for I2C, P_JMP and 5V supply. All useful pins have been made available, but you can also remove or not use any pads you don't require in the library.
The P_JMP pins on the board can be used to connect the VCC rails on each port to an external supply. When using the P_JMP pins, you have to consider how it will be connected. The "before" pins on the P_JMP connector go to the 3.3/5V power supply on the Port MuxR board and the "after" pins connect to the controllable VCC pins on all the ports.To visualise this, if you refer to the block diagram, the "before" connection is the bottom of the PWR jumper block and the "after" connection is the top of this block. Normally a jumper bridges these two pins together on the Port MuxR board.
On the adapter boards we have released, there is an option for either an external supply or using the onboard supply. This is facilitated through an additional user settable jumper (see example below). This jumper must removed if using an external supply in this instance.
If using an external supply, there is a 5V limit for the controllable VCC lines.
The 5V pin can be used to provide power to the board instead of using the USB port. Please note if using it in this configuration, there is no reverse voltage protection on the pins on the Port MuxR, so please be careful when using this in your design. This also bypasses the current limiter, so you will need a supply that can support a 220uF capacitance on startup if using other devices, to prevent a dropout on startup.
When interfacing with the I2C lines, you will require pullup resistors to allow it to work correctly.