stm32: support pin input interrupts

src/machine/machine_stm32_gpio_reva.go

@@ -0,0 +1,92 @@
+// +build stm32,!stm32l4,!stm32l5
+
+package machine
+
+import (
+	"device/stm32"
+)
+
+// This variant of the GPIO input interrupt logic is for
+// chips with a smaller number of interrupt channels
+// (that fits in a single register).
+
+//
+// STM32 allows one interrupt source per pin number, with
+// the same pin number in different ports sharing a single
+// interrupt source (so PA0, PB0, PC0 all share).  Only a
+// single physical pin can be connected to each interrupt
+// line.
+//
+// To call interrupt callbacks, we record here for each
+// pin number the callback and the actual associated pin.
+//
+
+// Callbacks for pin interrupt events
+var pinCallbacks [16]func(Pin)
+
+// The pin currently associated with interrupt callback
+// for a given slot.
+var interruptPins [16]Pin
+
+// SetInterrupt sets an interrupt to be executed when a particular pin changes
+// state. The pin should already be configured as an input, including a pull up
+// or down if no external pull is provided.
+//
+// This call will replace a previously set callback on this pin. You can pass a
+// nil func to unset the pin change interrupt. If you do so, the change
+// parameter is ignored and can be set to any value (such as 0).
+func (p Pin) SetInterrupt(change PinChange, callback func(Pin)) error {
+	port := uint32(uint8(p) / 16)
+	pin := uint8(p) % 16
+
+	enableEXTIConfigRegisters()
+
+	if callback == nil {
+		stm32.EXTI.IMR.ClearBits(1 << pin)
+		pinCallbacks[pin] = nil
+		return nil
+	}
+
+	if pinCallbacks[pin] != nil {
+		// The pin was already configured.
+		// To properly re-configure a pin, unset it first and set a new
+		// configuration.
+		return ErrNoPinChangeChannel
+	}
+
+	// Set the callback now (before the interrupt is enabled) to avoid
+	// possible race condition
+	pinCallbacks[pin] = callback
+	interruptPins[pin] = p
+
+	crReg := getEXTIConfigRegister(pin)
+	shift := (pin & 0x3) * 4
+	crReg.ReplaceBits(port, 0xf, shift)
+
+	if (change & PinRising) != 0 {
+		stm32.EXTI.RTSR.SetBits(1 << pin)
+	}
+	if (change & PinFalling) != 0 {
+		stm32.EXTI.FTSR.SetBits(1 << pin)
+	}
+	stm32.EXTI.IMR.SetBits(1 << pin)
+
+	intr := p.registerInterrupt()
+	intr.SetPriority(0)
+	intr.Enable()
+
+	return nil
+}
+
+func handlePinInterrupt(pin uint8) {
+	if stm32.EXTI.PR.HasBits(1 << pin) {
+		// Writing 1 to the pending register clears the
+		// pending flag for that bit
+		stm32.EXTI.PR.Set(1 << pin)
+
+		callback := pinCallbacks[pin]
+		if callback != nil {
+			callback(interruptPins[pin])
+		}
+	}
+}