Added external interrupt and test to determine impedance. Not working yet.

src/ad5940_registers.rs

@@ -28,13 +28,20 @@ bitflags! {
     #[derive(Clone, Copy)]
     #[derive(PartialEq)]
     pub struct SWCON: u32 {
+        const T9CON         = 1 << 17; // T9 switch // RTIA switch
+        const TMUXCON_MSK   = 0b1111 << 12;
+        const TMUXCON_T2    = 0b0010 << 12; // T2 switch
+        const TMUXCON_TR1   = 0b1000 << 12; // TR1 switch
         const NMUXCON_MSK   = 0b1111 << 8;
         const NMUXCON_N2    = 0b0010 << 8; // N2 switch
         const NMUXCON_N5    = 0b0101 << 8; // N5 switch
+        const NMUXCON_NR1   = 0b1010 << 8; // NR1 switch
         const PMUXCON_MSK   = 0b1111 << 4;
+        const PMUXCON_PR0   = 0b0001 << 4; // PR0 switch
         const PMUXCON_P2    = 0b0010 << 4; // P2 switch
         const PMUXCON_P11   = 0b1011 << 4; // P11 switch
         const DMUXCON_MSK   = 0b1111;
+        const DMUXCON_DR0   = 0b0001; // DR0 switch
         const DMUXCON_D5    = 0b0101; // D5 switch
     }
 }