How to make work this LCD Screen with my FEZ Mini?

Archive
1

I am trying to use this device :
http://www.aliexpress.com/item/Free-shipping-2pcs-IIC-I2C-TWI-Serial-LCD-1602-Module-Shield-Display-with-Test-code-Yellow/580397625.html
I had no luck yet, I have been trying with the code from Pavel :
http://bansky.net/blog/2008/10/interfacing-lcd-using-i2c-port-extender/

any idea ? suggestions ?
thanks in advance :slight_smile:
Steve

2

Show us how do you connect it to mini.

3

Hello

Mini => Screen
SCA => SCA + 1k8 Pull up res to 5V
SCL => SCL + 1k8 Pull up res to 5V

Seem’s the screen receives something but i can just get strange chars or the backlight turn’s on/off…
I tried to reverse bit order but it doesn’t help.

Steve

4

SDA not SCA :slight_smile:

5

SCA and SCL pins on mini have required pull-ups already. Try connecting the screen directly.

Here is Mini schematics for your convenience.

http://www.ghielectronics.com/downloads/FEZ/Mini/FEZMini_sch.pdf

6

How, that’s a good thing.

but i have been trying during 2 days without the pull-ups.

i don’t know where to search…

7

Like this, right?

Mini => Screen
SDA => SDA
SCL => SCL

Can you snap a picture of your wiring?

8

OK, when I’ll be home, i’ll make a picture.

thanks, already for your precious support :slight_smile:

9

You are welcome :slight_smile:

10

Photo of my wiring…

http://www.flickr.com/photos/stevemettraux/7950549672/sizes/l/in/photostream/

i know i m not that good at soldering :slight_smile:

11

Looks about right.

Connections all good, no cold joints?

If you have an Arduino, I would try the example arduino code as well to make sure the display is good.

12

hello,
i checked and redone some joints. no luck.

i took another mini and another screen, made this :
http://www.flickr.com/photos/stevemettraux/7954049582/sizes/l/in/photostream/
still no luck… :frowning:

13

i am starting to guess why it’s not working the wiring on my hardware (screen) doesn’t correspond to the “bansky” wiring…

my chip PCF8574T is connected like this :

PCF8574T => LCD
7 => D7
6 => D6
5 => D5
4 => D4

But “bansky” connected it to :
7 => D3
6 => D2
5 => D1
4 => D0

but knowing that the bytes must be cut in 4 by 4, and maybe the order should be reversed (no idea) and that they have to be mixed with commands and orders,
i am puzzled. it would be easier to find the code in .NET.

14

I made it work :slight_smile:

it was in fact the wiring. instead to put the command on the first 4 bits ( on the left). I had to put them on the right and shift the data to the left…

thanks architect for your support, you helped me to keep courage on this one :slight_smile:

15

Sorry, don’t understand what difference you’re talking about - the D numbers are the same??!!

The PCF8574 is just an I2C IO module. Simplistically, you clock in 8 bits of data, then it presents those 8 bits as a single byte (across the 8 output wires). So what we need to do is make sure you present the right sequence of bits to the IO expander, so it presents the right sequence of bytes to the device. If you don’t have the same “bit-wire” connected to the LCD controller as the Bansky code sends, then you need to rearrange that appropriately.

Of course, the I2C adapter is just that, an adapter. You could hijack the raw HD44780 pins on the LCD and prove that works if you wanted to (but it’ll use a few more pins :slight_smile: )

16

Ah cool, glad to hear you sorted it out - while I was typing ! :slight_smile:

17

thanks, Brett. I’ve corrected the post about the numbering :slight_smile: