From 3c0a6fc53ba1d21367309d6e6ed36e87dc33d10c Mon Sep 17 00:00:00 2001
From: Ethan Zonca <ethanzonca@ethanzonca.com>
Date: Fri, 13 Jan 2023 14:50:52 -0500
Subject: [PATCH] Disable interrupts during critical period

---
 inc/system.h      |  3 +++
 src/system.c      | 17 +++++++++++++++++
 src/usbd_cdc_if.c |  2 ++
 3 files changed, 22 insertions(+)

diff --git a/inc/system.h b/inc/system.h
index 48d7884..7fb639a 100644
--- a/inc/system.h
+++ b/inc/system.h
@@ -4,5 +4,8 @@
 
 void system_init(void);
 void system_hex32(char *out, uint32_t val);
+void system_irq_enable(void);
+void system_irq_disable(void);
+
 
 #endif
diff --git a/src/system.c b/src/system.c
index b9a14ab..59712de 100644
--- a/src/system.c
+++ b/src/system.c
@@ -86,3 +86,20 @@ void system_hex32(char *out, uint32_t val)
 		p--;
 	}
 } 
+
+
+// Disable all interrupts
+void system_irq_disable(void)
+{
+        __disable_irq();
+        __DSB();
+        __ISB();
+}
+
+
+// Enable all interrupts
+void system_irq_enable(void)
+{
+        __enable_irq();
+}
+
diff --git a/src/usbd_cdc_if.c b/src/usbd_cdc_if.c
index 077003f..78e4b9a 100644
--- a/src/usbd_cdc_if.c
+++ b/src/usbd_cdc_if.c
@@ -167,6 +167,7 @@ static int8_t CDC_Receive_FS (uint8_t* Buf, uint32_t *Len)
 // Process incoming USB-CDC messages from RX FIFO
 void cdc_process(void)
 {
+	system_irq_disable();
 	if(rxbuf.tail != rxbuf.head)
 	{
 		//  Process one whole buffer
@@ -201,6 +202,7 @@ void cdc_process(void)
 		// Move on to next buffer
 		rxbuf.tail = (rxbuf.tail + 1) % NUM_RX_BUFS;
 	}
+	system_irq_enable();
 }