1602A lcd display in i2c displays nothing

[DRoss4]

Hi all, I soldered a PCF8574AT serial converter on a 1602A lcd display and connected it to my Edison module with Arduino Breakout board.

The backlight turns on as expected. Using i2cdetect I can find the chip address at 0x3f:

Now I try to run this simple code in Eclipse:

# include "lcm1602.h"

# include

# include "mraa.hpp"

int main() {

upm::Lcm1602* lcd = new upm::Lcm1602(6, 0x3f);

lcd->setCursor(1,1);

lcd->write("Hello World");

sleep(5);

delete lcd;

return 0;

}

But nothing is displayed. Both methods setCursor and write get mraa::SUCCESS ar result.

Using bus 0,1, and 6 or a random address in the Lcm1602 constructor changes nothing.

Same result if I connect the module to A4 and A5 pins or to SCL and SDA pins on the breakout board.

Setting the cursor in (0,0), (2,2), etc. doesn't help.

Any thoughts?

[DRoss4 · Accepted solution]

Today I gave it another try, but the device seemed to be disappeared from the i2c bus:

At that moment I was enabling the i2c bus using these commands:

echo 27 > /sys/class/gpio/export

echo 28 > /sys/class/gpio/export

echo mode1 > /sys/kernel/debug/gpio_debug/gpio27/current_pinmux

echo mode1 > /sys/kernel/debug/gpio_debug/gpio28/current_pinmux

But while googling for a fix, I found here http://www.emutexlabs.com/project/215-intel-edison-gpio-pin-multiplexing-guide http://www.emutexlabs.com/project/215-intel-edison-gpio-pin-multiplexing-guide that these commands should be used:

echo 28 > /sys/class/gpio/export

echo 27 > /sys/class/gpio/export

echo 204 > /sys/class/gpio/export

echo 205 > /sys/class/gpio/export

echo 236 > /sys/class/gpio/export

echo 237 > /sys/class/gpio/export

echo 14 > /sys/class/gpio/export

echo 165 > /sys/class/gpio/export

echo 212 > /sys/class/gpio/export

echo 213 > /sys/class/gpio/export

echo 214 > /sys/class/gpio/export

echo low > /sys/class/gpio/gpio214/direction

echo low > /sys/class/gpio/gpio204/direction

echo low > /sys/class/gpio/gpio205/direction

echo in > /sys/class/gpio/gpio14/direction

echo in > /sys/class/gpio/gpio165/direction

echo low > /sys/class/gpio/gpio236/direction

echo low > /sys/class/gpio/gpio237/direction

echo in > /sys/class/gpio/gpio212/direction

echo in > /sys/class/gpio/gpio213/direction

echo mode1 > /sys/kernel/debug/gpio_debug/gpio28/current_pinmux

echo mode1 > /sys/kernel/debug/gpio_debug/gpio27/current_pinmux

echo high > /sys/class/gpio/gpio214/direction

...And voilà the device came back on the i2c bus 6.

Then I rewrote my project in Java:

public class JavaTest {

static {

try {

System.loadLibrary("javaupm_i2clcd");

} catch (UnsatisfiedLinkError e) {

System.err.println("error in loading native library");

System.exit(-1);

}

}

public static void main(String[] args) throws InterruptedException {

upm_i2clcd.Lcm1602 lcd = new upm_i2clcd.Lcm1602(0, 0x3f);

lcd.setCursor(0, 0);

lcd.write("Hello World!");

}

}

And... magically it worked!

Still have to realize what I did to have it working, but I'm leaving it here for someone else like me to find it.