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