From bb8d6e0ad2709096d8d56f5a314b0abe0e57fa25 Mon Sep 17 00:00:00 2001
From: Markus Hitter <mah@jump-ing.de>
Date: Mon, 25 Apr 2016 00:28:51 +0200
Subject: [PATCH] Display: create and use display_set_cursor().

Having this in a seperate function will be helpful later.
---
 display.h         |  4 +++-
 display_ssd1306.c | 22 +++++++++++++++++++---
 i2c_test.c        |  3 ++-
 3 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/display.h b/display.h
index 786ea2d..7215c34 100644
--- a/display.h
+++ b/display.h
@@ -34,6 +34,8 @@
 
 void display_init(void);
 void display_clear(void);
-void display_text_P(uint8_t line, uint8_t column, PGM_P message_P);
+
+void display_set_cursor(uint8_t line, uint8_t column);
+void display_text_P(PGM_P message_P);
 
 #endif /* _DISPLAY_H */
diff --git a/display_ssd1306.c b/display_ssd1306.c
index e52e1b0..fd5b029 100644
--- a/display_ssd1306.c
+++ b/display_ssd1306.c
@@ -78,10 +78,16 @@ void display_clear(void) {
 }
 
 /**
-  Prints the text at a given position.
+  Sets the cursor to the given position.
+
+  \param line   The vertical cursor position to set, in lines. First line is
+                zero. Line height is character height, which is currently
+                fixed to 8 pixels.
+
+  \param column The horizontal cursor position to set, in pixels. First
+                column is zero.
 */
-void display_text_P(uint8_t line, uint8_t column, PGM_P message) {
-  uint8_t i, index;
+void display_set_cursor(uint8_t line, uint8_t column) {
 
   // Enter command mode.
   displaybus_write(0x00, 0);
@@ -90,6 +96,16 @@ void display_text_P(uint8_t line, uint8_t column, PGM_P message) {
   // Set column.
   displaybus_write(0x00 | (column & 0x0F), 0);
   displaybus_write(0x10 | ((column >> 4) & 0x0F), 1);
+}
+
+/**
+  Prints the text at the current cursor position.
+
+  \param message Zero terminated string of the text to be displayed, stored
+                 in program memory.
+*/
+void display_text_P(PGM_P message) {
+  uint8_t i, index;
 
   // Render text to bitmap to display.
   displaybus_write(0x40, 0);
diff --git a/i2c_test.c b/i2c_test.c
index 48527e3..7d74f75 100644
--- a/i2c_test.c
+++ b/i2c_test.c
@@ -24,7 +24,8 @@ static void i2c_test(void) {
     "Welcome to Teacup" is 64 pixel columns wide, entire display is
     128 columns, so we offset by 32 columns to get it to the center.
   */
-  display_text_P(1, 32, PSTR("Welcome to Teacup"));
+  display_set_cursor(1, 32);
+  display_text_P(PSTR("Welcome to Teacup"));
 }
 
 #endif /* I2C_TEST */