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Access to the RS485



Dear All,
 
I tried to open ("/dev/ttyS3", O_RDWR | NOCTTY), but the return is -1. I checked in previous messages and found that I should enable the RS485 first in the kernelconfig.
 
My questions are
 
1:) Shall I edit the kernelconfig file or kernelconfig.latest?
 
2:) Shall I enable RS485 or SER3 or both in the config file?
 
3:) Regarding the LCD driver sample provided in the the axis developer website, shall I also add "CONFIG_ETRAX_LCD_HD44780 = y" in the kernelconfig file?
 
4:) Whether should I use lcd_open ( ) or just open("/dev/lcd", ...) to open the LCD device? And also lcd_write( ) or just write ( ) to write to the block device.
 
Sorry for so many questions, but I am quite new with driver programming.
 
Great thanks for your help.
 
Regards,
 
Wang Kangning