From 825be9d121a9c698bf60bbdc384f2eeaf66f60d0 Mon Sep 17 00:00:00 2001
From: tmk <hasu@tmk-kbd.com>
Date: Tue, 2 Dec 2014 22:47:59 +0900
Subject: [PATCH] Disable input buffer for ADC

---
 keyboard/hhkb_rn42/rn42/battery.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/keyboard/hhkb_rn42/rn42/battery.c b/keyboard/hhkb_rn42/rn42/battery.c
index 0320e1ba..720d63be 100644
--- a/keyboard/hhkb_rn42/rn42/battery.c
+++ b/keyboard/hhkb_rn42/rn42/battery.c
@@ -21,6 +21,10 @@ void battery_init(void)
     ADMUX = (1<<REFS1) | (1<<REFS0);
     ADCSRA = (1<<ADPS2) | (1<<ADPS1) | (1<<ADPS0);
     ADCSRA |= (1<<ADEN);
+    // digital input buffer disable(24.9.5)
+    DIDR0 = (1<<ADC0D) | (1<<ADC4D) | (1<<ADC5D) | (1<<ADC7D);
+    DIDR1 = (1<<AIN0D);
+    DIDR2 = (1<<ADC8D) | (1<<ADC9D) | (1<<ADC11D) | (1<<ADC12D) | (1<<ADC13D);
 
     // ADC disable voltate divider(PF4)
     DDRF  |=  (1<<4);
-- 
2.39.3