2 replies to this topic

[garethconner]

Hi folks,

 

I'm spending my first "real" day with the Netduino 2 Plus.  I've got a 4x20 OLED character display from New Haven (NHD-0420DZW-AY5).  This is a similar display to ones we use in some of our products with Rabbit micros.  In other products we use these displays in 8-bit parallel mode and hang them on the Rabbit data bus, but I'm trying to conserve pins on my Netduino so I thought I could re-configure the display for SPI as per the data sheet.

 

My difficulty is that the the command words for the display are 10-bits wide (RS, RW, D7..D0).  I'm a little foggy about how to send a 10-bit word via the SPI class.  It looks like there is an overload for SPI#WriteRead that accepts a writeOffset & writeCount, so I thought perhaps I could hand it a 16-bit value with an writeOffset=0 and a writeCount=10.  This is a code snippet:

        public static void InitOLED()        {            UInt16[] readBuffer = new UInt16[1];            var config = new SPI.Configuration(Pins.GPIO_PIN_A4,                 false,                150,                150,                true,                true,                ((1/3) * 10000),                SPI_Devices.SPI1                );            _oled = new SPI(config);            Thread.Sleep(100);            //Display OFF            _oled.WriteRead(new UInt16[] { 0x08 }, 0, 10, readBuffer, 0, 8, 0);

When run, the last line that contains the WriteRead call generates the following exception:

An unhandled exception of type 'System.ArgumentException' occurred in Microsoft.SPOT.Hardware.dll

I'm clearly doing something silly, but can't see what I've done wrong.  Any help would be greatly appreciated.  Thanks!

[Mario Vernari]

The Netduino (Plus) 2 cannot manage SPI-data sized other than 8 or 16 bits.

I suggest to follow (or take inspiration) from the article I have written a while ago. I used a trick to achieve a non-standard data size, yet yielding pretty decent performance.

http://tinyclr.it/su...r-netduino.aspx

Have a nice Christmas!

[garethconner]

Hi Mario,

 

Thanks very much for you answer.  That is a very clever solution.  I may steal back some the io pins with an io expander and revert to a 4-bit parallel interface for the display.  However, it's good to see that the 10-bit SPI protocol is possible with some hacking.

 

Merry Christmas (belated) and happy New Year!