Problem with hd44780 controlled via I2C PCF8574 [Solved] - Raspberry Pi Forums

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hey there,
have little problem i2c converter , lcd. i'm using wiringpi library , works except of backlight. figured out gpio -x pcf8574:100:0x20 write 103 1 command turns light on. tried use function digitalwrite (103,1) , after cout<<digitalread(103) , shows 0. suggestions i'm doing wrong? it's code:

image

karl9955 wrote:hey there,
have little problem i2c converter , lcd. i'm using wiringpi library , works except of backlight. figured out gpio -x pcf8574:100:0x20 write 103 1 command turns light on. tried use function digitalwrite (103,1) , after cout<<digitalread(103) , shows 0. suggestions i'm doing wrong? it's code:
image
how backlight connected pcf8574?
(most pcf8574-based interfaces** use {pnp} buffer transistor, partially because device "open drain" , can sink significant current - implies "common anode" backlight, active low when used unbuffered connection)
trev.
** example these backpacks:
http://www.cpmspectrepi.webspace.virgin ... d_backpack
http://www.cpmspectrepi.webspace.virgin ... d_backpack
http://www.cpmspectrepi.webspace.virgin ... d_backpack


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