Merge #400

400: Make SPI clock pin optional for use with WS2812 r=jonas-schievink a=aelray

smart-leds-rs uses SPI without clock for controlling WS2812 LEDs.

Co-authored-by: aelray <aelray@gmail.com>

Author: bors[bot]

nrf-hal-common/src/spi.rs

@@ -93,10 +93,14 @@ where
 
     #[cfg(feature = "51")]
     fn set_pins(spi: &mut T, pins: Pins) {
-        spi.pselsck
-            .write(|w| unsafe { w.bits(pins.sck.pin().into()) });
-
-        // Optional pins.
+        spi.pselsck.write(|w| unsafe {
+            if let Some(ref pin) = pins.sck {
+                w.bits(pin.pin().into())
+            } else {
+                // Disconnect
+                w.bits(0xFFFFFFFF)
+            }
+        });
         spi.pselmosi.write(|w| unsafe {
             if let Some(ref pin) = pins.mosi {
                 w.bits(pin.pin().into())
@@ -118,11 +122,9 @@ where
 
     #[cfg(not(feature = "51"))]
     fn set_pins(spi: &mut T, pins: Pins) {
-        spi.psel
-            .sck
-            .write(|w| unsafe { w.bits(pins.sck.pin().into()) });
-
-        // Optional pins.
+        if let Some(ref pin) = pins.sck {
+            spi.psel.sck.write(|w| unsafe { w.bits(pin.pin().into()) });
+        }
         if let Some(ref pin) = pins.mosi {
             spi.psel.mosi.write(|w| unsafe { w.bits(pin.pin().into()) });
         }
@@ -140,7 +142,9 @@ where
 /// GPIO pins for SPI interface.
 pub struct Pins {
     /// SPI clock.
-    pub sck: Pin<Output<PushPull>>,
+    ///
+    /// None if unused.
+    pub sck: Option<Pin<Output<PushPull>>>,
 
     /// MOSI Master out, slave in.
     ///