New driver

[HondaRulez]

Hi,
any docs about how to add a new driver ?

I have a 170x40 VFD graphic display, the display have parellel interface similar to a SRAM or so.. address, data also have some other i/o.
currently due the limited I/O pins on the host side I made a I2C interface.
the display works perfectly.
My goal is using U8g2 to draw items and use different sizes of the fonts on this display.
so I would add this one to the drivers and use the lib as usual on other devices.

Thanks.

[olikraus]

What is your exact type of VFD?
U8g2 beta release contains support for a GU800 128x64 VFD, see also here: #1604

U8G2_GU800_128X64_1_4W_SW_SPI u8g2(U8G2_R0, /* clock=*/ 13, /* data=*/ 11, /* cs=*/ 10, /* dc=*/ 9, /* reset=*/ 8);
U8G2_GU800_128X64_1_4W_HW_SPI u8g2(U8G2_R0, /* cs=*/ 10, /* dc=*/ 9, /* reset=*/ 8);

You can download the latest U8g2 beta release from here: https://github.com/olikraus/U8g2_Arduino/archive/master.zip
Arduino IDE:

1. Remove the existing U8g2_Arduino library (https://stackoverflow.com/questions/16752806/how-do-i-remove-a-library-from-the-arduino-environment)
2. Install the U8g2_Arduino Zip file via Arduino IDE, add zip library menu (https://www.arduino.cc/en/Guide/Libraries).

PlatformIO:
platformio.ini (https://docs.platformio.org/en/latest/projectconf/section_env_library.html#lib-deps) should include

lib_deps =
  u8g2=https://github.com/olikraus/U8g2_Arduino/archive/master.zip

[olikraus]

U8g2 provides a communication interface for you, however your case I assume it is better to hardcode everything: This means you can ignore all kind of GPIO assignments.
For example in the A2 driver you can see this command to transfer the bitmap data to the display:

u8g2/csrc/u8x8_d_a2printer.c

Line 109 in ef9fa9f

u8x8_cad_SendData(u8x8, c, ptr); /* c, note: SendData can not handle more than 255 bytes, send one line of data */

In your case you need to write a replacement for u8x8_cad_SendData which transfers data via your i2c interface ot the VFD.
As decribed above the x y position is stored in ((u8x8_tile_t *)arg_ptr) if you receive the DRAW_TILE message. From the x y pos you need to calculate the address of the data byte location in the VFD.

[HondaRulez]

ok, some files are "generated" like u8g2_d_memory.c and u8g2_d_setup.c, so I need to edit a template somwhere or I can edit directly these files ? or how the file generation works ?

[olikraus]

ok, some files are "generated" like u8g2_d_memory.c and u8g2_d_setup.c, so I need to edit a template somwhere or I can edit directly these files ? or how the file generation works ?

Code Generation is not required if you follow my suggestions from above.
My suggested procedure u8g2_m_22_9_f already exists but is bigger than required. The code generatore would probably generate a new procedure u8g2_m_22_5_f which would fit better, but you could also write this u8g2_m_22_5_f by your own.

Also the setup procedure can be written by yourself. So, no need to generate anything.

[HondaRulez]

sorry for the dumb questions :) I just like to knows the backgrounds what I doing :)
naming scheme...

uint8_t *u8g2_m_22_9_1(uint8_t *page_cnt)
{
#ifdef U8G2_USE_DYNAMIC_ALLOC
*page_cnt = 1;
return 0;
#else
static uint8_t buf[176];
*page_cnt = 1;
return buf;
#endif
}
this functions allocate only 176 bytes (I expected 198)

also what means the 22 the 9 and the 'f'

checking some other drivers I would declare 170_5_4

because the LCD have 4 individual display pages and 1 data byte covers 1 column and 8 lines.

[olikraus]

The code generate creates those functions, based on the size of the displays, so each display will have its own memory allocation function. Of course those functions are reused as much as possible (so two displays with the same dimension will share the same memory function).

The memory function look like this: u8g2_m_22_9_f

22: The width of the display in tiles ( (width_in_pixel + 7) / 8) (176 pixel in your case)
9: Tile height ( (height_in_pixel + 7) / 8 )

The f at the end tells u8g2 the type of data upload to the display:
1: only one page can be rendered and uploaded to the display (picture loop, slower but lesser RAM required)
f: the full display memory is mirrored in u8g2. User can use the send command to upload the complete data to the display (faster, but more RAM required)

A page is defined as one tile row, which is 8 pixel height and 170 pixel width in your case
The number of pages has to be returned in *page_cnt
So in your case, if you want all your graphics beeing rendered in the uC you need to set page_cnt = 5;
(58=40 pixel)

Lets make more practical examples:
*page_cnt = 1 (one page of display memory in uC) --> 176 bytes required
*page_cnt = 5 (full display memory in uC) --> 880 bytes requred

There are some programming differences if your use this full memory approach vs. one page approach (see U8g2 Manual).