lkml.org 
[lkml]   [2018]   [Feb]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 2/2] auxdisplay: charlcd: make home command unshift display
Date
A user has no way of unshifting the display programmatically once shifted.
Users cannot rely on ^[[H (home) to result in their message being seen either.
Use the actual HOME command 0x02 instead of only returning to x0/y0.
Users can still do ^[[Lx0y0; (go to x/y) if they wish to use the 'old' home
function.
Implement fast clearing of LCD by going to x0/y0 first, clearing display and
then calling home to possibly unshift display possibly avoiding artifacts by
not unshifting before clearing display.

Signed-off-by: Robert Abel <rabel@robertabel.eu>
---
drivers/auxdisplay/charlcd.c | 28 ++++++++++++++++++++++++++--
1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c
index ae078f414539..fdb3aa6423bf 100644
--- a/drivers/auxdisplay/charlcd.c
+++ b/drivers/auxdisplay/charlcd.c
@@ -43,6 +43,8 @@
/* LCD commands */
#define LCD_CMD_DISPLAY_CLEAR 0x01 /* Clear entire display */

+#define LCD_CMD_HOME 0x02 /* Set DDRAM address to 0 and unshift display */
+
#define LCD_CMD_ENTRY_MODE 0x04 /* Set entry mode */
#define LCD_CMD_CURSOR_INC 0x02 /* Increment cursor */

@@ -174,13 +176,24 @@ static void charlcd_gotoxy(struct charlcd *lcd)
lcd->ops->write_cmd(lcd, LCD_CMD_SET_DDRAM_ADDR | addr);
}

+/**
+ * charlcd_home() - Return to DDRAM address 0 and unshift the display.
+ * @lcd: LCD descriptor structure.
+ *
+ * Return to coordinates x0/y0 and unshift the display.
+ *
+ * Note: Use the movement command ^[[Lx0y0; instead of home
+ * in case the display should not be unshifted.
+ */
static void charlcd_home(struct charlcd *lcd)
{
struct charlcd_priv *priv = to_priv(lcd);

+ /* return to x0/y0 and unshift the display */
priv->addr.x = 0;
priv->addr.y = 0;
- charlcd_gotoxy(lcd);
+ lcd->ops->write_cmd(lcd, LCD_CMD_HOME);
+ long_sleep(2);
}

static void charlcd_print(struct charlcd *lcd, char c)
@@ -198,11 +211,21 @@ static void charlcd_print(struct charlcd *lcd, char c)
charlcd_gotoxy(lcd);
}

+/**
+ * charlcd_clear_fast() - Perform a fast clear of the display and return home.
+ * @lcd: LCD descriptor structure.
+ *
+ * The display will be unshifted and at coordinates x0/y0 after fast clear.
+ */
static void charlcd_clear_fast(struct charlcd *lcd)
{
+ struct charlcd_priv *priv = to_priv(lcd);
int pos;

- charlcd_home(lcd);
+ /* avoid artifacts by going to x0/y0 without unshifting the display */
+ priv->addr.x = 0;
+ priv->addr.y = 0;
+ charlcd_gotoxy(lcd);

if (lcd->ops->clear_fast)
lcd->ops->clear_fast(lcd);
@@ -210,6 +233,7 @@ static void charlcd_clear_fast(struct charlcd *lcd)
for (pos = 0; pos < min(2, lcd->height) * lcd->hwidth; pos++)
lcd->ops->write_data(lcd, ' ');

+ /* return to x0/y0 and unshift the display */
charlcd_home(lcd);
}

--
2.11.0
\
 
 \ /
  Last update: 2018-02-28 01:07    [W:0.119 / U:0.144 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site