ST7565 LCD notes - Revision history

Morris at 08:48, 17 January 2012

2012-01-17T08:48:02Z

Morris at 08:46, 17 January 2012

2012-01-17T08:46:01Z

Morris at 08:45, 17 January 2012

2012-01-17T08:45:43Z

Morris: Created page with "this is pretty good, if you can spare the memory. the display runs on 3.3vdc and draws very little power. This display plus a 328p in powerdown draw 177 uA. Unfortunately unl…"

2012-01-17T08:45:06Z

Created page with "this is pretty good, if you can spare the memory. the display runs on 3.3vdc and draws very little power. This display plus a 328p in powerdown draw 177 uA. Unfortunately unl…"

New page

this is pretty good, if you can spare the memory.
the display runs on 3.3vdc and draws very little power.
This display plus a 328p in powerdown draw 177 uA.
Unfortunately unless you want to get very clever you
need a large (1k) buffer to hold the display bitmap.
it's organized as 8 rows, each of which is 128 columns,
like this:

<pre>
||||||||||||||||||||||||||| ...
||||||||||||||||||||||||||| ...
...
</pre>

so for instance a 0xFF in location 0 shows a vertical
bar in the top left corner of the screen.

This works out ok for a 5x7 text font but i'll still need
to implement scrolling, etc. The display seems to have
some builtin assistance for this but i need to figure
it out.

Backlight is white LED @25mA. Display contrast is decent
but not spectacular.

** It should be possible to do plain 21x8 text without using
a bitmap buffer. This would only be 168 bytes to hold the
whole screen of text.

you can write a line of text without any buffer at all,
because you send data to the display as 128 vertical 1 pixel
wide columns all the way across the screen, so you just send
the character bitmaps as you go.
you'd only need to buffer data to scroll the screen upward
to make room for a new line at the bottom. To do that you
don't need to remember the top line, since it's getting
thrown out anyway, so that's only 147 chars to buffer.

maybe write a function for writing a line of text to a line of
display bitmap, define an array to hold the text, and some
functions like stlcd_putchar(c) for updating the array.

it would be nice to be able to write one character at a time
to the display since you don't want to have to write full
lines (or the whole screen) at a time, though the update
time may be fast enough that it doesn't matter.
maybe write chars to the display immediately when putchar
is called, and simultaneously update the backing array so
we can update if we have to scroll.

also make sure everything that touches the display asserts and
deasserts CS so other things can live on the SPI bus.
a magnetometer or DS3234 might be good for playing with.

** should try driving the backlight directly off a GPIO. they
can source 20mA which is about what it draws, so it might work.
Also, if you put it on one of the OCR outputs you can PWM it
at high freq to make it as dim or bright as you want.

** an additional bigger font would be really nice.

@@ Line 2: / Line 2: @@
 the display runs on 3.3vdc and draws very little power.
 This display plus a 328p in powerdown draw 177 uA.
-Unfortunately unless you want to get very clever you
+Unfortunately unless you want to get clever you
 need a large (1k) buffer to hold the display bitmap.
 it's organized as 8 rows, each of which is 128 columns,
@@ Line 21: / Line 21: @@
 it out.
-Backlight is white LED @25mA.  Display contrast is decent
+Backlight is white LED @25mA.  Display contrast is decent but not spectacular.
 * It should be possible to do plain 21x8 text without using
@@ Line 49: / Line 48: @@
 also make sure everything that touches the display asserts and
-deasserts CS so other things can live on the SPI bus.
+deasserts CS so other things can live on the SPI bus. .
 * should try driving the backlight directly off a GPIO. they can source 20mA which is about what it draws, so it might work. Also, if you put it on one of the OCR outputs you can PWM it at high freq to make it as dim or bright as you want.
 * an additional bigger font would be really nice.

@@ Line 24: / Line 24: @@
 but not spectacular.
-** It should be possible to do plain 21x8 text without using
+* It should be possible to do plain 21x8 text without using
 a bitmap buffer. This would only be 168 bytes to hold the
 whole screen of text.
@@ Line 31: / Line 31: @@
 because you send data to the display as 128 vertical 1 pixel
 wide columns all the way across the screen, so you just send
-the character bitmaps as you go.
+the character bitmaps as you go. you'd only need to buffer data to scroll the screen upward
 to make room for a new line at the bottom. To do that you
 don't need to remember the top line, since it's getting

@@ Line 53: / Line 53: @@
 a magnetometer or DS3234 might be good for playing with.
-** should try driving the backlight directly off a GPIO. they
+* should try driving the backlight directly off a GPIO. they can source 20mA which is about what it draws, so it might work. Also, if you put it on one of the OCR outputs you can PWM it at high freq to make it as dim or bright as you want.
-** an additional bigger font would be really nice.
+* an additional bigger font would be really nice.