From a5ee1ba4b3a4efae0a77c4f07be4de78fad057fc Mon Sep 17 00:00:00 2001
From: deadprogram <ron@hybridgroup.com>
Date: Mon, 28 Dec 2020 15:33:09 +0100
Subject: [PATCH] machine/nrf52840: ensure that USB CDC interface is only
 initialized once

Signed-off-by: deadprogram <ron@hybridgroup.com>
---
 src/machine/board_circuitplay_bluefruit.go |  2 +-
 src/machine/board_clue_alpha.go            |  2 +-
 src/machine/board_feather-nrf52840.go      |  2 +-
 src/machine/board_itsybitsy-nrf52840.go    |  2 +-
 src/machine/board_particle_argon.go        |  2 +-
 src/machine/board_particle_boron.go        |  2 +-
 src/machine/board_particle_xenon.go        |  2 +-
 src/machine/usb_nrf52840.go                | 11 +++++++++--
 8 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/src/machine/board_circuitplay_bluefruit.go b/src/machine/board_circuitplay_bluefruit.go
index cb56ed34..bc6d6172 100644
--- a/src/machine/board_circuitplay_bluefruit.go
+++ b/src/machine/board_circuitplay_bluefruit.go
@@ -58,7 +58,7 @@ const (
 
 // UART0 is the USB device
 var (
-	UART0 = USB
+	UART0 = &USB
 )
 
 // I2C pins
diff --git a/src/machine/board_clue_alpha.go b/src/machine/board_clue_alpha.go
index d90b6889..cb458062 100644
--- a/src/machine/board_clue_alpha.go
+++ b/src/machine/board_clue_alpha.go
@@ -105,7 +105,7 @@ const (
 
 // UART0 is the USB device
 var (
-	UART0 = USB
+	UART0 = &USB
 )
 
 // I2C pins
diff --git a/src/machine/board_feather-nrf52840.go b/src/machine/board_feather-nrf52840.go
index f353a3b7..ae4b54e0 100644
--- a/src/machine/board_feather-nrf52840.go
+++ b/src/machine/board_feather-nrf52840.go
@@ -77,7 +77,7 @@ const (
 
 // UART0 is the USB device
 var (
-	UART0 = USB
+	UART0 = &USB
 )
 
 // I2C pins
diff --git a/src/machine/board_itsybitsy-nrf52840.go b/src/machine/board_itsybitsy-nrf52840.go
index e61be006..4d98b669 100644
--- a/src/machine/board_itsybitsy-nrf52840.go
+++ b/src/machine/board_itsybitsy-nrf52840.go
@@ -72,7 +72,7 @@ const (
 
 // UART0 is the USB device
 var (
-	UART0 = USB
+	UART0 = &USB
 )
 
 // I2C pins
diff --git a/src/machine/board_particle_argon.go b/src/machine/board_particle_argon.go
index 5401c4ad..44e5a51b 100644
--- a/src/machine/board_particle_argon.go
+++ b/src/machine/board_particle_argon.go
@@ -41,7 +41,7 @@ const (
 
 // UART
 var (
-	Serial = USB
+	Serial = &USB
 	UART0  = NRF_UART0
 )
 
diff --git a/src/machine/board_particle_boron.go b/src/machine/board_particle_boron.go
index cb05e725..a50d87eb 100644
--- a/src/machine/board_particle_boron.go
+++ b/src/machine/board_particle_boron.go
@@ -41,7 +41,7 @@ const (
 
 // UART
 var (
-	Serial = USB
+	Serial = &USB
 	UART0  = NRF_UART0
 )
 
diff --git a/src/machine/board_particle_xenon.go b/src/machine/board_particle_xenon.go
index c1614636..7a94cf6d 100644
--- a/src/machine/board_particle_xenon.go
+++ b/src/machine/board_particle_xenon.go
@@ -41,7 +41,7 @@ const (
 
 // UART
 var (
-	Serial = USB
+	Serial = &USB
 	UART0  = NRF_UART0
 )
 
diff --git a/src/machine/usb_nrf52840.go b/src/machine/usb_nrf52840.go
index e5132335..8d056839 100644
--- a/src/machine/usb_nrf52840.go
+++ b/src/machine/usb_nrf52840.go
@@ -12,8 +12,9 @@ import (
 
 // USBCDC is the USB CDC aka serial over USB interface on the nRF52840
 type USBCDC struct {
-	Buffer    *RingBuffer
-	interrupt interrupt.Interrupt
+	Buffer       *RingBuffer
+	interrupt    interrupt.Interrupt
+	initcomplete bool
 }
 
 // WriteByte writes a byte of data to the USB CDC interface.
@@ -87,6 +88,10 @@ func exitCriticalSection() {
 
 // Configure the USB CDC interface. The config is here for compatibility with the UART interface.
 func (usbcdc *USBCDC) Configure(config UARTConfig) {
+	if usbcdc.initcomplete {
+		return
+	}
+
 	// Enable IRQ. Make sure this is higher than the SWI2 interrupt handler so
 	// that it is possible to print to the console from a BLE interrupt. You
 	// shouldn't generally do that but it is useful for debugging and panic
@@ -107,6 +112,8 @@ func (usbcdc *USBCDC) Configure(config UARTConfig) {
 	)
 
 	nrf.USBD.USBPULLUP.Set(0)
+
+	usbcdc.initcomplete = true
 }
 
 func (usbcdc *USBCDC) handleInterrupt(interrupt.Interrupt) {