From d9b831fcc29585eab34c58c5a67c060d886bc8a6 Mon Sep 17 00:00:00 2001
From: Erich Eckner <git@eckner.net>
Date: Thu, 1 Nov 2018 11:20:07 +0100
Subject: multiplexer: set up pull-up resistor on SENSE_PIN

---
 multiplexer.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

(limited to 'multiplexer.c')

diff --git a/multiplexer.c b/multiplexer.c
index b260891..9bfdf1b 100644
--- a/multiplexer.c
+++ b/multiplexer.c
@@ -198,6 +198,17 @@ void multiplexer_setup_non_root(t_display_data *display_data)
   INP_GPIO(PAR_CLK_PIN);
   OUT_GPIO(PAR_CLK_PIN);
   INP_GPIO(SENSE_PIN);
+  // enable pull-up on SENSE_PIN
+  /** adopted from wiringPi's wiringPi/wiringPi.c lines 1507-1511 **/
+  *(gpio + GPPUD) = 2; // bit 0: pull down; bit 1: pull up
+  usleep(5);
+  *(gpio + gpioToPUDCLK[SENSE_PIN]) = 1 << (SENSE_PIN & 31);
+  usleep(5);
+  *(gpio + GPPUD) = 0;
+  usleep(5);
+  *(gpio + gpioToPUDCLK[SENSE_PIN]) = 0;
+  usleep(5);
+  /** end of adoption **/
 #endif
 
   for (int i=0; i<3; i++)
-- 
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