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RCAT-1A Rev A3 Designer’s manual
Serious Power for the Serious Designer
As illustrated, J4 gives you direct access to CPU ports PF4, PF5, PF6 and PF7. In addition you can access the board
ground, the CPU reset pin (/RST) and board Vcc. Pins 7 and 8 on J4 are not connected to anything.
SPI Connector
Similar to J4, discussed above, connector J1 serves a dual purpose. It gathers all the signals together that are
required for use in the CPU’s SPI system. See the ATMega™ manual for details on this. Alternatively, J1 presents
several ports for direct access. Here is the schematic:
Figure 26
As shown, J1 gives you direct access to CPU ports PB1, PB2, and PB3 along with Vcc, /RST, and GND access.
USART 0
There are no direct connection paths between USART0 and any connector on the RCAT™. All access to USART0 is
peformed through the USB, RS232 or RS422/485 interfaces.
USART 2 Port – J14 and J7
A complete discussion of the USART ports follows in the next sections. However, if you are not using the usarts,
most of them have direct access to their associated CPU port pins. J14 are J7 are is two of those. This is, perhaps,
the most challenging serial port on the board to understand, so we will show the annotated schematic to aid
you:
