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O-Family
Joined: 23 May 2010
Posts: 320
Location: Japan
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 Posted: Sat Mar 20, 2021 1:19 am Post subject: Question of 'AN #118 - I2C LCD and Keboard library' |
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Don't you think the initialization signal is strange for the I2C LCD library using PCF8574?
Is this a phenomenon only for my hardware?
The output result is different from the parameter of "Lcd_i2c.lib".
There is also a difference in the initialization of the LCD controller HD44780 data sheet.
(BASCOM-AVR version : 2.0.8.3 ) |
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O-Family
Joined: 23 May 2010
Posts: 320
Location: Japan
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| Posted: Tue Mar 23, 2021 4:07 am Post subject: |
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In 'lcd_i2c.LIB'.
The '* BASIC: waitms 4' line seems to corrupt the contents of the variable '_temp1'.
I think that some LCDs may fail to initialize.
Also, is register R24 and variable '_temp1' overlaid in the '_write_lcd_byte:' routine?
I don't understand that '_temp1' is restored when pop R24. |
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laborratte
Joined: 27 Jul 2005
Posts: 299
Location: Berlin
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| Posted: Tue Mar 23, 2021 11:53 am Post subject: |
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comparing your measurements and the code _temp1 is clearly an alias for R24 or R25. As R24 and R25 are used and changed in *BASIC: waitms 4, _temp1 has the value of &h00 after waitms, that is corresponding to you measurement.
I would suggest a bugfix by adding a additional Ldi _temp1, &h03 like:
| Code: |
(...)
[_Init_LCD]
_Init_LCD:
*BASIC: waitms 50
ldi r16,&hc0 ; this is to make the initialization on both halfs of a 4-line LCD
Ldi _temp1, &h03 ; at init-time I call all routines before _lcd_e is loaded into r16
Rcall _Send_to_LCD
*BASIC: waitms 4
Ldi _temp1, &h03 ; reset _temp1 with the value as it is deleted in waitms
Rcall _Send_to_LCD
Rcall _Send_to_LCD
(...)
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O-Family
Joined: 23 May 2010
Posts: 320
Location: Japan
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| Posted: Wed Mar 24, 2021 2:49 am Post subject: |
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Thank you for checking.
I think the fix will improve it too.
Also,'bl_lcd_i2c.LIB' with backlight control has the same bug.
We are currently editing a new library to include additional features. |
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Paulvk
Joined: 28 Jul 2006
Posts: 1257
Location: SYDNEY
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| Posted: Wed Mar 24, 2021 9:50 am Post subject: |
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It would have been nice to have an I2C library using two PCF8574s for the basic graphic displays these use a lot of pins.
The bugs may explain some of the intermittent odd things I have experienced.
Regards Paul |
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O-Family
Joined: 23 May 2010
Posts: 320
Location: Japan
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| Posted: Wed Mar 24, 2021 2:29 pm Post subject: |
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| I think the graphic LCD is possible with this MCP23017 board. |
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SZTRAD
Joined: 30 Dec 2019
Posts: 165
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| Posted: Wed Mar 24, 2021 4:20 pm Post subject: |
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Yes, it is.
The standard alphanumeric LCD is usable in this configurationwithout any problem.
Refresh for graphic is at the level of standard I2C graphic display.
RS |
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albertsm
Joined: 09 Apr 2004
Posts: 5921
Location: Holland
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| Posted: Wed Mar 24, 2021 8:53 pm Post subject: |
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instead of using waitms you can use waitUS , of course adjusting the value a factor 1000.
waitus does not trash regs.
_________________
Mark |
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