This week I spent most of my time finishing up the schematics. The updated board will have 2 complete SPI and 1 complete UART connection, between the PIC32 and the FPGA. The PIC32 pin availability for these connections can be checked from harmony configurator in MPLABX. You might need to modify the connection settings in order to see all the different possibilities such as SS pin in an SPI connection and URTS, UCTS pins in a UART connection.
Pin Position Considerations
In the FPGA most of the pins are used as normal I/O pins, thus the pins can be swapped. This gives the PCB designer the ability to freely move the connections at will. The same can be said about the PIC32. In this case, there are more limitations such as the RMII (Ethernet ) connection which uses a fixed set of pins and the ADC pins which are very few and should be connected to the analogue port.
Changes Made To The Board
- There are added connections between the PIC32 and the FPGA (2x SPI and 1x UART).
- TQG packaging is used instead of FTG for the FPGA.
- A new power supply design is being used.
- The power indicator LED is now connected to a transistor.
- The SD-card connection to the FPGA is shifted to minimise track length.
- Most of the connections on both the FPGA and the PIC32 are modified and have to be updated in the software.
- A smaller memory size PIC32 will be used in the new design. However, the pin out, stays exactly the same.