Date: Fri, 22 Oct 2021 08:38:54 -0300 From: "Dr. Rolf Jansen" <freebsd-rj@obsigna.com> To: freebsd-arm@freebsd.org Subject: Re: Using 20x4 LCD display Message-ID: <031FB1DF-6B2A-4122-AC5B-34E921995284@obsigna.com> In-Reply-To: <wu7o87h1rhk.fsf@banyan.cs.ait.ac.th> References: <wu7o87h1rhk.fsf@banyan.cs.ait.ac.th>
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--Apple-Mail=_E0FE9533-D6FE-4CCA-A1C8-D86EA3735A40 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=utf-8 > Am 22.10.2021 um 03:52 schrieb Olivier <Olivier.Nicole@cs.ait.ac.th>: >=20 > I would like to use a 20x4 LCD display attached to a Raspberry Pi > running FreeBSd 12.2. >=20 > I can talk to the display through the I2C interface, when I send > something the back light will turn off and on, so the link is > established. I use a 20x4 LCD (HD44780 type) over I2C (via PCF8574T) on a BeagleBone = Black. For this, I manually transcribed one of the many Python libraries = into plain C, and I wrote a minimalistic I2C glue interface in C, so it = can be easily addressed. I just put a .zip file for downloading it on my web site: https://obsigna.com/Downloads/LCD_20x4_over_I2C.zip I added a Hello World test program (s. below). Perhaps you need to = change the I2C device number and the I2C address in lcd.c. Here I have: uint8_t lcd_iicid =3D 1; uint8_t lcd_addr =3D 0x27; The Python code contained a lot of delays between various calls. This = was not necessary for the BeagleBone Black, I removed this and it let me = optimize the subroutines for transferring data to the display. I don=E2=80= =99t know whether this would work on a Raspberry Pi, though. Compile it with: cc i2c.c lcd.c hello.c -o hello Run it with: ./hello #include <stdio.h> #include <stdlib.h> #include <stdint.h> #include <unistd.h> #include "i2c.h" #include "lcd.h" int main(int argc, const char *argv[]) { lcd_begin(); lcd_print("Hello, World!", 13); lcd_setCursor(0, 1); lcd_print("HD44780 over PCF8574", 20); lcd_setCursor(0, 2); lcd_print("If it does not work,", 20); lcd_setCursor(0, 3); lcd_print("do not ask me why.", 18); return 0; } Best regards Rolf Dr. Rolf Jansen - - Rua Reginaldo de Lima, 98 Parque S=C3=A3o Diogo 09732-550, S=C3=A3o Bernardo do Campo S=C3=A3o Paulo - Brazil Phone: 0055-11/4317-0974 Mobile: 0055-11/9 8141-1465 E-Mail: rj@obsigna.com <mailto:rj@obsigna.com> BLog: obsigna.com <https://obsigna.com/>; --Apple-Mail=_E0FE9533-D6FE-4CCA-A1C8-D86EA3735A40--
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