How to use Digole SPI Text-LCD Display Adapter

[Niro]

Hi guys,

I'm working on a new project over the holidays and hoping someone could give me some help to start it...

I bought a Digole SPI Text-LCD Display Adapter (V2), as it seems to be very versatile and quite cheap.
http://www.digole.com/index.php?productID=551
It should be used for a 4x20 LCD Display to save some wires and pins of my controller (ATmega328).

As I'm not really familiar to SPI, maybe someone could give me some help to get it work.

Many thanks!!
Niro

[Benj]

Hi Niro,

SPI is quite nice to use once you get used to it. There is a blog here which should help to familiarise yourself with how SPI works and how to implement your own protocol to communicate with any SPI device.

http://www.matrixtsl.com/blog/simplifie ... c-and-spi/

Let us know how your getting on.

[Niro]

Hi Benj,

many thanks, very interesting.
I'll keep you updated...

Niro

[Niro]

Hi Benj,

it is working quite well now, but I really had problems in the beginning with SS_ pin (Slave select, low active).
As you can see in the picture, SS_ is connected to pin B2 (port B, bit 2) of the ATmega328. This is the only way it is working.
For my complete circuit some more SPI-components are needed, like an external EE, so I would need some different SS_ pins.
Trying to get the display work with SS_ on pin B1 (I replaced B2 with B1 in Flowcode), it does not work at all!

Would you please give me some advice how go on?

Many Thnaks,
Niro

[Benj]

Hi Niro,

SPI Master on an AVR device can lock up if the hardware SPI SS pin is left as an input and allowed to read as a logic 0. This puts the SPI into Slave mode which locks any subsequent SPI communications.

AVR_SS.jpg (55.23 KiB) Viewed 5179 times

To get around this you can.

1) Use the hardware SS pin as your SPI Master Chip Select pin

2) Output a 0 or a 1 to the hardware SS pin before starting any SPI communications.

3) Use a pull up resistor or internal pull up to ensure the pin is always read as a logic 1.

4) Use software SPI channel, not ideal.

Note this problem is only present on Atmel AVR hardware. PICs for example have a Master/Slave control bit in the SPI control registers.