muxed
0 uart0_tx spi0_sclk uart2_tx uart3_tx
1 uart0_rx spi0_mosi uart2_rx uart3_rx
-2 twi0_sda spi0_ss
+2 twi0_sda spi0_ss
3 twi0_scl spi0_miso
+8 sd0_clk sd1_clk
+9 sd0_cmd sd1_cmd
+10 sd0_d0 sd1_d0
+11 sd0_d1 sd1_d1
+12 sd0_d2 sd1_d2
+13 sd0_d3 sd1_d3
dedicated
4 uart1_tx
5 uart1_rx