Handle debugger pins

At startup, pins used by the debugger are in `Debugger` state, prohibiting their
use. `disable_jtag` allow to get PA15, PB3 and PB4 usable as GPIO or alternate
functions at the cost of disabling JTAG.

CHANGELOG.md

@@ -20,6 +20,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Breaking changes
 
 - ADC now requires the clock configuration for intialisation
+- `disable_jtag` now transforms PA15, PB3 and PB4 to forbid their use without desactivating JTAG
 
 ### Changed
 

examples/nojtag.rs

@@ -17,12 +17,20 @@ fn main() -> ! {
     let p = pac::Peripherals::take().unwrap();
 
     let mut rcc = p.RCC.constrain();
+    let mut gpioa = p.GPIOA.split(&mut rcc.apb2);
     let mut gpiob = p.GPIOB.split(&mut rcc.apb2);
     let mut afio = p.AFIO.constrain(&mut rcc.apb2);
 
-    afio.mapr.disable_jtag();
+    let (pa15, pb3, pb4) = afio.mapr.disable_jtag(gpioa.pa15, gpiob.pb3, gpiob.pb4);
 
-    gpiob.pb4.into_push_pull_output(&mut gpiob.crl).set_low();
+    let mut pa15 = pa15.into_push_pull_output(&mut gpioa.crh);
+    let mut pb3 = pb3.into_push_pull_output(&mut gpiob.crl);
+    let mut pb4 = pb4.into_push_pull_output(&mut gpiob.crl);
 
-    loop {}
+    loop {
+        pa15.toggle();
+        pb3.toggle();
+        pb4.toggle();
+        cortex_m::asm::delay(8_000_000);
+    }
 }

examples/pwm_input.rs

@@ -25,9 +25,10 @@ fn main() -> ! {
     let mut afio = p.AFIO.constrain(&mut rcc.apb2);
     let mut dbg = p.DBGMCU;
 
-    let mut gpiob = p.GPIOB.split(&mut rcc.apb2);
+    let gpioa = p.GPIOA.split(&mut rcc.apb2);
+    let gpiob = p.GPIOB.split(&mut rcc.apb2);
 
-    let pb4 = gpiob.pb4;
+    let (_pa15, _pb3, pb4) = afio.mapr.disable_jtag(gpioa.pa15, gpiob.pb3, gpiob.pb4);
     let pb5 = gpiob.pb5;
 
     let pwm_input = p.TIM3.pwm_input(

src/afio.rs

@@ -3,6 +3,14 @@ use crate::pac::{afio, AFIO};
 
 use crate::rcc::APB2;
 
+use crate::gpio::{
+    Debugger,
+    Input,
+    Floating,
+    gpioa::PA15,
+    gpiob::{PB3, PB4},
+};
+
 pub trait AfioExt {
     fn constrain(self, apb2: &mut APB2) -> Parts;
 }
@@ -54,10 +62,22 @@ impl MAPR {
         unsafe { &(*AFIO::ptr()).mapr }
     }
 
-    /// Disables the JTAG to free up pb3, pb4 and pa15 for normal use
-    pub fn disable_jtag(&mut self) {
+    /// Disables the JTAG to free up pa15, pb3 and pb4 for normal use
+    pub fn disable_jtag(
+        &mut self,
+        _pa15: PA15<Debugger>,
+        _pb3: PB3<Debugger>,
+        _pb4: PB4<Debugger>
+    ) -> (
+        PA15<Input<Floating>>,
+        PB3<Input<Floating>>,
+        PB4<Input<Floating>>,
+    ) {
         self.mapr()
-            .modify(|_, w| unsafe { w.swj_cfg().bits(0b010) })
+            .modify(|_, w| unsafe { w.swj_cfg().bits(0b010) });
+
+        // NOTE(unsafe) zero sized type, and recreated in its initial state
+        unsafe { core::mem::MaybeUninit::uninit().assume_init() }
     }
 }
 

src/gpio.rs

@@ -18,6 +18,8 @@ pub struct Input<MODE> {
     _mode: PhantomData<MODE>,
 }
 
+/// Used by the debugger (type state)
+pub struct Debugger;
 /// Floating input (type state)
 pub struct Floating;
 /// Pulled down input (type state)
@@ -503,17 +505,17 @@ gpio!(GPIOA, gpioa, gpioa, iopaen, ioparst, PAx, [
     PA10: (pa10, 10, Input<Floating>, CRH),
     PA11: (pa11, 11, Input<Floating>, CRH),
     PA12: (pa12, 12, Input<Floating>, CRH),
-    PA13: (pa13, 13, Input<Floating>, CRH),
-    PA14: (pa14, 14, Input<Floating>, CRH),
-    PA15: (pa15, 15, Input<Floating>, CRH),
+    PA13: (pa13, 13, super::Debugger, CRH),
+    PA14: (pa14, 14, super::Debugger, CRH),
+    PA15: (pa15, 15, super::Debugger, CRH),
 ]);
 
 gpio!(GPIOB, gpiob, gpioa, iopben, iopbrst, PBx, [
     PB0: (pb0, 0, Input<Floating>, CRL),
     PB1: (pb1, 1, Input<Floating>, CRL),
     PB2: (pb2, 2, Input<Floating>, CRL),
-    PB3: (pb3, 3, Input<Floating>, CRL),
-    PB4: (pb4, 4, Input<Floating>, CRL),
+    PB3: (pb3, 3, super::Debugger, CRL),
+    PB4: (pb4, 4, super::Debugger, CRL),
     PB5: (pb5, 5, Input<Floating>, CRL),
     PB6: (pb6, 6, Input<Floating>, CRL),
     PB7: (pb7, 7, Input<Floating>, CRL),