A few days before being done with this display hardware decided
say good bye. Accordingly I can't continue with writing related
code. Writing down what already works and what's still missing is
probably a good idea, to make sure the next fellow doesn't have
to investigate from scratch.
Currently not implemented because this costs additional binary
size and, well, with I2C being reliable now, it's difficult to
test it. And also because I'm lazy :-)
Now we shouldn't experience wait cycles in i2c_write() during
typical display writes any longer. It should also distribute CPU
load of display writes a lot better.
Previously writing a line of text to the display would take
almost as long as it took to actually send it to the display,
because the I2C queue could hold only one transmission, which
effectively meant only one character. This could hold the main
loop for several milliseconds.
Now we queue characters, send them one by one, and return to the
main loop in between.
This costs 160 bytes program memory. Only 18 bytes RAM, because
the I2C queue was reduced accordingly. Now:
Program: 24456 bytes
Data: 1543 bytes
EEPROM: 32 bytes
This isn't pretty at all, but it shows the principle.
Unfortunately it also exploits a bug in the I2C sending mechanism,
I2C sending hangs a few seconds after reset.
You see where the journey is going? This is the equivalent to the
function to write a character to the serial line, so we can
basically swap these two in other functions.
Monospaced fonts require a bit less space, right now it saves a
nice 110 bytes binary size.
Actually, the distinction between monospaced and proportional
fonts was in font.h already, so not supporting them was a bug.
But so far we have no monospaced font, so nobody noticed.
Note by Traumflug: this code was written by Ruslan Popov a lot
earlier already. I picked it to i2c_test.c to get "something"
visible running. This is the commit finally adjusted to the new
display infrastructure.
Markus Hitter
Ruslan Popov