document how to build a solenoid driver and install a solenoid

* In contrast to the relay breakout board I was using before,
  the solenoid driver is HIGH-active, so some code had to be changed
  as well.

1 files changed, 2 insertions, 2 deletions

diff --git a/matrix.c b/matrix.c
index 47623f7..4c1cea9 100644
--- a/matrix.c
+++ b/matrix.c
@@ -293,10 +293,10 @@ static void init_pins(void)
     PORTF &= ~0b00001000;
 
     /*
-     * Solenoid (ie. relay). It's LOW-active.
+     * Solenoid
      */
     DDRB  |= (1 << PB3);
-    PORTB |= (1 << PB3);
+    PORTB &= ~(1 << PB3);
 }
 
 static void select_col(uint8_t col)