muxed
-0 uart0_tx spi0_sclk
-1 uart0_rx spi0_mosi
-2 twi0_sda spi0_ss
-3 twi0_scl spi0_miso
+0 uart0_tx spi0_sclk
+1 uart0_rx spi0_mosi
+2 twi0_sda spi0_ss
+3 twi0_scl spi0_miso
dedicated
-4 uart1_tx
-5 uart1_rx
+4 uart1_tx
+5 uart1_rx
+6 twi1_sda
+7 twi1_scl