From 6680caddf2a16ef662a158defbb2320d57a5e5ba Mon Sep 17 00:00:00 2001
From: Daniel Friesel <daniel.friesel@uos.de>
Date: Thu, 30 Apr 2020 12:30:53 +0200
Subject: MSP430 gpio.setup: Avoid unintentional short circuits

---
 include/arch/msp430fr5994lp/driver/gpio.h | 33 ++++++++++++++++++++++---------
 1 file changed, 24 insertions(+), 9 deletions(-)

(limited to 'include/arch/msp430fr5994lp/driver')

diff --git a/include/arch/msp430fr5994lp/driver/gpio.h b/include/arch/msp430fr5994lp/driver/gpio.h
index aa32e7e..d42dace 100644
--- a/include/arch/msp430fr5994lp/driver/gpio.h
+++ b/include/arch/msp430fr5994lp/driver/gpio.h
@@ -23,7 +23,22 @@ class GPIO {
 			PIN_INVALID
 		};
 
+		/*
+		 * Set all non-standard GPIOs to input with pull-down.
+		 * This avoids excessive current draw due to floating inputs.
+		 * Note that we do not set GPIOs to output low, as that might
+		 * short-circuit other peripherals.
+		 */
 		inline void setup() {
+			P1DIR = BIT0 | BIT1; // red LED, green LED
+			P2DIR = 0;
+			P3DIR = 0;
+			P4DIR = 0;
+			P5DIR = 0;
+			P6DIR = 0;
+			P7DIR = 0;
+			P8DIR = 0;
+			PJDIR = 0;
 			P1OUT = 0;
 			P2OUT = 0;
 			P3OUT = 0;
@@ -33,15 +48,15 @@ class GPIO {
 			P7OUT = 0;
 			P8OUT = 0;
 			PJOUT = 0;
-			P1DIR = BIT0 | BIT1 | 0xff; // red LED, green LED
-			P2DIR = 0xff ^ (BIT0 | BIT1); // UART
-			P3DIR = 0xff;
-			P4DIR = 0xff;
-			P5DIR = 0xff;
-			P6DIR = 0xff;
-			P7DIR = 0xff;
-			P8DIR = 0x0f;
-			PJDIR = BIT6 | BIT7; // HFXT (not populated)
+			P1REN = 0xff & ~(BIT0 | BIT1); // red LED, green LED
+			P2REN = 0xff & ~(BIT0 | BIT1); // UART
+			P3REN = 0xff;
+			P4REN = 0xff;
+			P5REN = 0xff;
+			P6REN = 0xff;
+			P7REN = 0xff;
+			P8REN = 0xff;
+			PJREN = BIT6 | BIT7; // HFXT (not populated)
 		}
 		inline void led_on(unsigned char id) {
 			if (id == 0) {
-- 
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