Posted by Mike P on 20 October 2011 - 10:45 AM in General Discussion

I wish I had a solution to your problem but Mario has already suggested everything I can think of.

The bug Mario refers to would only affect you if you used clock_idle=true. This is because the SPI firmware always sets clock to false after the transaction.
The bug has no effect if using clock_idle=false.
The WS2801 spec says it's good for up to 25MHz clock speed. Don't try to set 25MHz though because you will end up with 48MHz. You should be able to use 24MHz though if you keep lead length short. But there's no reason that 2MHz shouldn't work.

You could try running the strip at Vcc=4V or less. Add a couple of 1N4007 diodes in series to drop the voltage. The chip is spec'd for 3.3-5V VCC but obviously the LED intensity would be lower. This would only be to prove that the logic hi level is not the issue.
For those reading this thread who haven't looked at the data sheet the specification for a logical high input level is 0.8* Vcc. With Vcc at 5v this means a minimum voltage of 4v is required to be certain it is registered as logic hi. Netduino can only put out 3.3v on the outputs.

Since your chip does not use the CS, you should use CS = GPIO_None. Pin 13 on the mini is the only pin that you can't use for CS (with the currently released firmware) the same is true for Pin 4 on the netduino(&plus)
This is due to some functionality in the .NETMF porting kit that was abandoned but not completely removed.
I can't see how this could stop your code from working though.
Are you using the latest firmware? 4.1.0.6 or 4.2?

If I were you, I would buy myself an Open bench logic sniffer from Seeed studios. It'll be the best $50 you've ever spent.
A logic shrimp or a bus pirate might even be sufficient. Or borrow an oscilloscope from someone.

I duplicated Stefan W's sample on my Netduino plus (FW4.1.0.6) and got a different result.
Here is my sample taken using the Logic Sniffer

        public static void Main()
        {
            byte[] buffer = new byte[] { 0x55, 0xFF, 0X00, 0X55, 0XAA };
            SPI.Configuration xSPIConfig;
            SPI xspi;
            xSPIConfig = new SPI.Configuration(Pins.GPIO_NONE, false, 0, 0, false, true, 100, SPI.SPI_module.SPI1);
            xspi = new SPI(xSPIConfig);
            while (true)
            {
                xspi.Write(buffer);
                Thread.Sleep(100);
            }
        }

Even at 100kHz there is nothing like a 500us break in the transmission. The GC (garbage collector) may run between bytes during an SPI write comman making a slightly longer delay between bytes but it would never get to anything like 500us.

Posted by Mike P on 21 October 2011 - 09:08 PM in General Discussion

Posted by Mike P on 21 October 2011 - 09:38 AM in General Discussion

Posted by Mike P on 20 October 2011 - 06:07 PM in General Discussion

Posted by Mike P on 20 October 2011 - 06:17 PM in General Discussion

        public static void Main() 
        { 
            byte[] buffer = new byte[] { 0xFF,0x00, 0x00,  0x00,0xFF,0x00, 0x00,0x00,0xFF }; 
            SPI.Configuration xSPIConfig; 
            SPI xspi; 
            xSPIConfig = new SPI.Configuration(Pins.GPIO_NONE, false, 0, 0, false, true, 100, SPI.SPI_module.SPI1); 
            xspi = new SPI(xSPIConfig); 
            while (true) 
            { 
                xspi.Write(buffer); 
                Thread.Sleep(100); 
            } 
        }

Posted by Mike P on 21 October 2011 - 07:28 AM in General Discussion

Posted by Mike P on 21 October 2011 - 10:02 PM in General Discussion

Posted by Mike P on 21 October 2011 - 12:56 AM in General Discussion

Posted by Mike P on 26 July 2011 - 10:00 AM in Netduino Plus 2 (and Netduino Plus 1)

Posted by Mike P on 30 August 2011 - 09:47 PM in Netduino Plus 2 (and Netduino Plus 1)

Posted by Mike P on 13 October 2011 - 03:49 AM in Netduino Plus 2 (and Netduino Plus 1)

Posted by Mike P on 13 October 2011 - 03:41 AM in Netduino Plus 2 (and Netduino Plus 1)

3000 * adcValue / System.math.pow(2, 24)
3000.0 * adcValue / System.math.pow(2, 24)

Posted by Mike P on 15 September 2011 - 09:48 AM in Netduino 2 (and Netduino 1)

Posted by Mike P on 26 October 2011 - 03:31 AM in General Discussion

Posted by Mike P on 07 October 2011 - 07:57 AM in General Discussion

Hi Dan,
I think I can help you with a few things here.
The Spec sheet for MCP2515 gives the max SPI bus speed as 10MHz. Your configuration has a value of 16000 which is 16MHz. Try using 1000 10000 or less.
From the figure below the clock idle state is false and the clock edge is true.

However this chip supports both SPI Mode 0,0 and mode 1,1. So clock idle=true will also work. There is a bug with the current firmware that only affects clockidle=false so I would recommend you use clock idle=true
There is a bug with the current firmware that only affects clockidle=TRUE so I would recommend you use clock idle=FALSE (Sorry for the confusion)

Lastly the timing diagram(FIGURE 12-10) and the table that accompanies it (TABLE 13-6) show the maximum clock rate is 10MHz and the CS Setup Time and the CS Hold Time must be a minimum of 50ns.
Using a value of 0 for both these settings in your configuration will result in delays far exceding 50ns
So your config line should be:
config = new SPI.Configuration(Pins.GPIO_PIN_D10 , FALSE, 0, 0, TRUE, TRUE, 10000, SPI.SPI_module.SPI1);
config = new SPI.Configuration(Pins.GPIO_PIN_D10 , FALSE, 0, 0, FALSE, TRUE, 10000, SPI.SPI_module.SPI1);

Now for the read command.
Section 12.3 of the datasheet explains the read register process. It says that "The read operation is terminated by raising the CS pin"
It also says "The MCP2515 expects the first byte after lowering CS to be the instruction/command byte. This implies that CS must be raised and then lowered again to invoke another command."
By writing using 3 operations as you are doing the chip select will be raised between each operation.
So you need to combine the read instruction, address data and reading the result into one writeread operation.
The following code should do this:

        SPI.Configuration xSPIConfig;
        SPI xspi;
        xSPIConfig = new SPI.Configuration(Pins.GPIO_PIN_D10, false, 0, 0, false, true, 10000, SPI.SPI_module.SPI1);
        xspi = new SPI(xSPIConfig);
        private byte readReg(byte regno)
        {
            byte[] writeBuffer = new byte[] {0x03, regno};
            byte[] readBuffer = new byte[1];
            xspi.WriteRead(writeBuffer,readBuffer,2);
            return readBuffer[0];
        }

You can find some more info in the Wiki
Using-SPI-Write-and-WriteRead

Posted by Mike P on 29 August 2011 - 01:37 PM in General Discussion

Posted by Mike P on 30 August 2011 - 04:12 PM in General Discussion

Now I've got to put my money where my mouth is! This should work but untested I tried to put a table in below but the TABs get stripped out so it's in CSV form instead. The table below gives the resistor values, The total resistance when the button is pressed, The voltage on the analog input, The ADC reading, The difference between the ADC value for this button and the next one up, and the suggested cut-off value to use when deciding which button has been pressed I even managed to keep to common value resistors and get very even separation between the voltages. Vcc=3300mV Button,Resistor,Total R,mV,ADC,delta,cutoff Cancel,1500,1500,3300,1024,,986 Right,120,1620,3056,948,76,908 Left,150,1770,2797,867,81,827 Down,180,1950,2538,787,80,747 Up,220,2170,2281,707,80,668 Select,270,2440,2029,629,78,315 None,,,0,0,629, In the schematic the second analog input pin would actually be used as a digital interrupt pin and could be on any of the GPIO pins. Its not necessary if you don't mind polling the analog input continuously.

Posted by Mike P on 08 September 2011 - 04:29 AM in General Discussion

Posted by Mike P on 26 August 2011 - 09:09 AM in General Discussion

Posted by Mike P on 14 September 2011 - 12:08 AM in General Discussion

Posted by Mike P on 17 July 2011 - 11:41 AM in Project Showcase

            /// <summary>
            /// Gets an enumeration of the key press at the current time.
            /// Can only be used if the LCD has been initialised with the true parameter.
            /// </summary>
            /// <returns></returns>
            public static Keys GetKey()
            {
                if (!analogInitialised) throw new Exception("Analog input is not Initialised");

                int i = AnKey.Read();

                if (i > 910)//expected value = 1024
                    return Keys.None;

                if (i < 90)//expected value = 0
                    return Keys.Right;

                if (i < 290)//expected value = 184
                    return Keys.Up;

                if (i < 490)//expected value = 397
                    return Keys.Down;

                if (i < 690)//expected value = 578
                    return Keys.Left;
                //expected value = 796
                return Keys.Select;

            }

Posted by Mike P on 11 October 2011 - 06:20 AM in General Discussion

Posted by Mike P on 28 July 2011 - 11:35 AM in Netduino 2 (and Netduino 1)

Posted by Mike P on 28 July 2011 - 12:26 PM in Netduino 2 (and Netduino 1)

Posted by Mike P on 13 October 2011 - 08:33 PM in General Discussion