I am Having an issue with SPI on Netduino Plus 2, I wrote a small class that manages the 12-bit input for MCP4921 chipset. and for the most part it functions like a charm. I do however get weird flickers when I test the setup on a pair of LEDs (attached Breadboard Diagram.)
here is my code.
Main Program
using System;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using SecretLabs.NETMF.Hardware;
using SecretLabs.NETMF.Hardware.Netduino;
namespace SLAMainboard
{
class program
{
static SPI.Configuration SPI0 = new SPI.Configuration(Pins.GPIO_PIN_D10, false, 0, 0, true, false, 10000, SPI_Devices.SPI1);
static SPI.Configuration SPI1 = new SPI.Configuration(Pins.GPIO_PIN_D9, false, 0, 0, true, false, 10000, SPI_Devices.SPI1);
public static void Main()
{
OutputPort led = new OutputPort(Pins.ONBOARD_LED, false);
SPIFormater SPIform = new SPIFormater();
SPI SPIbus0 = new SPI(SPI0);
while (true)
{
led.Write(true);
for (int i = 4095; i > 0; i--)
{
SPIbus0.Config = SPI0;
byte[] tmp = new byte[2];
tmp = SPIform.SPIformater(i,false,true,false,false);
//Debug.Print(i + " - " + SPIform.toString() + " - [" + tmp.GetValue(1) + "][" + tmp.GetValue(0) + "]");
SPIbus0.Write(tmp);
//Thread.Sleep(10);
SPIbus0.Config = SPI1;
tmp = SPIform.SPIformater(Abs(4095 - i), false, true, false, false);
//Debug.Print(i + " - " + SPIform.toString() + " - [" + tmp.GetValue(1) + "][" + tmp.GetValue(0) + "]");
SPIbus0.Write(tmp);
//Thread.Sleep(10);
}
led.Write(false);
Thread.Sleep(200);
}
}
public static int Abs(int i)
{
if (i < 0)
{
return i * -1;
}
else
{
return i;
}
}
}
}
SPIFormater Class
using System;
using Microsoft.SPOT;
/*****************************************
* SPI 12-bit value Formatter
*
* Version: 1.0.0.0
* Created: 11/23/2012
* Updated: 11/24/2012
*
* Description: This Class was created to deal with MicroCHIP MCP492X Chip-Sets
* I have not found a library to help with the input, so I decided to
* write my own.
*
* The Code take the an input of integers from 1 - 4095 (12-bits unsigned) and
* returns a byte array of two, you do have the option of assigning your own
* control bits, or just using the default I use.
*
* 15th bit | AB -> 1- DACb, 0 DACa
* 14th bit | BUF -> 1 - Buffered, 0 - Unbuffered
* 13th bit | GA -> 1 - 1x ref Voltage, 0 - 2x Ref Voltage
* 12th bit | SHDN -> 1 - Output Power Down Control Bit, 0 - Output Buffer Disabled, Out High Impedance
*
* ***************************************/
namespace SLAMainboard
{
class SPIFormater
{
Boolean[] bitArray;
public byte[] SPIformater(int valueInt, Boolean SHDN, Boolean GA,Boolean BUF,Boolean AB) // Formatter for MicroCHIP MCP492X chip set
{
int cntVal = 0; //counter value
bitArray = new Boolean[] { false, false, false, false, false, false, false, false, false, false, false, false, SHDN, GA, BUF, AB}; //0,0,0,0,0,0,0,0,0,0,0,0,|SHDN,GA,BUF,AB| <-- control bits
Boolean[] tmpArray = new Boolean[16];
if (valueInt > 4095 || valueInt < 0) // value has to in the range of 0 - 4095
{
return null; // Fail case
}
while (valueInt > 0)
{
if (valueInt % 2 != 0)
{
bitArray[cntVal] = true; // If remainder of division by 2 is not zero that bit is 1
}
else
{
bitArray[cntVal] = false; // If remainder of division by 2 is zero that bit is 0
}
valueInt /= 2; // divide by two, a binary left shift.
cntVal++; // next array value.
}
cntVal = 15;
for (int i = 0; i < 16; i++) // inverse the array so it would match the MicoCHIP Docs.
{
tmpArray[i] = bitArray[cntVal];
cntVal--;
}
bitArray = tmpArray;
return new byte[] { boolToByte(bitArray, 0), boolToByte(bitArray, 8) }; // return an array of two bytes from array of 16 bits.
}
public byte[] SPIformater(int valueInt) //defaults that I used for my project
{
return SPIformater(valueInt, true, true, true, false);
}
private byte boolToByte(Boolean[] inBool, int index) // takes array Boolean, and generates a byte from its subset.
{
if (inBool.Length - index - 8 < 0)
{
return 0;
}
byte b = 0;
for (int i = index; i < index + 8; i++)
{
b = (byte)(b << 1);
if (inBool[i])
{
b |= 1;
}
}
return b;
}
public string toString()
{
string s = "";
for (int i = 0; i < bitArray.Length; i++)
{
if (bitArray[i] == true)
{
s += 1;
}
else
{
s += 0;
}
}
return s;
}
}
}
Attached Files
-
NETduinoPLUS2SPI.png 114.85KB
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