The ammount of current being dumped into the interrupt is not a issue, what you should be worried about is the ammount of current being drawn on the outputport driving the columns. Even in that case, the ammount of current is negligable. Worstcase for any one driver would be 4 keys. If you are seriously worried about it you can mitigate the problem by driving the 4 rows and have the Columns as the interrupts, in that case the worse case would be 3 keys.

Yes, and it's bedtime for sure

Chris

I noticed the spec's http://www.netduino....oplus/specs.htm say the microSD holds up to 2Gb. Is this because the Plus uses SPI to talk to the SD card or is it a software limit?

So we have a good start on solving the problem. We have two of four things verified. 1. The display works, this was demonstrated by the successful use of the display with serial connections. 2. The driver on Fezzer works as it has been successfully used with SPI, I2C and Serial be several people with the Newhaven serial displays. This leaves us with just two things to verify: 1. The shorting block on the Newhaven display is correctly soldered. 2. The connections for I2C between the Netdiuno and the display are correct. Since the thread does not specifically identify the Netduino, I will go with the assumption that we are talking about a Netduion classic. So the connection between the Netduino and the Display would be as follows: Netduino Pin -> Display 5vdc -> 10 Gnd -> 9 A4 -> 8 A5 -> 7 I did not show a picture of the R1 jumper, because it is clearly displayed in the manual. However, I have attached a picture of the display working and its connections.

I have a Newhaven display running in .NETMF, you can look a working code on http://www.fezzer.co...ial-lcd-display . While this was done FEZ Panda, the code should work on Netduino. Give it a look. I will try it with the Netduino tomorrow morning myself so I can post a demon with the Netduino

Ok, I just got up and tried my driver on the Netduino. In fact I used my latest demo program I use for debuging driver improvements and the only thing I had to change was a few "using" statements and references.
If you start from "New project" paste the embedded code to you programs.cs, you would only have to add a reference to the Newhaven Displays class.

using System;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using SecretLabs.NETMF.Hardware;
using SecretLabs.NETMF.Hardware.Netduino;

namespace Netduino_With_Newhaven_Display
{
    public class Program
    {
        private static NewhavenDisplay.SerialLCD display;
        private static I2CDevice bus;

        static void sendFunction(byte[] data)
        {
            I2CDevice.I2CTransaction[] xAct = new I2CDevice.I2CTransaction[] { I2CDevice.CreateWriteTransaction(data) };
            int bytes = bus.Execute(xAct, 1000);
        }
        public static void Main()
        {
            bus = new I2CDevice(new I2CDevice.Configuration(0x50 >> 1, 100));
            display = new NewhavenDisplay.SerialLCD(sendFunction);
            display.Clear();
            display.Write("Well did it work?");
            display.Write("Lets see what happens with this one");
        }
    }
}

The problem is that when a pwm period and duration are the same the output is high. Period is the rising edge to rising edge time of the output wave form. While duration is the length of the high time of the period. So period should be 1/frequency and duration should be (duty_cycle * period) where duty cycle is some value < 1. Also if I remember correctly, period is in microseconds so:

Try

  var period = (uint)(1000000 / frequency); 
  pwm.SetPulse(period, period/2); 
 

I used the same buzzer and I just checked my code and the period is in microseconds like I remembered.

I got your latest code to work by adding a pull-up resister on ~RESET(pin18). Not too obvious in the description in table 1-1 "Hardware reset. Must be externally biased" I sort-of had it working without the pull up but it was not reliable. Once I put the resister in there, it became extreemly reliable. Sorry I didn't notice this before. And by the way, I had it working without any of the code changes I suggested. http://www.vimeo.com/20357391

I have had some success using I2C and I have the data sheet for the MCP23017 here in front of me so I think you are doing things right. I will have to get my hands on one the the chips to be sure.

First, the address should be in the range of 0x20 - 0x27. With the way it is wired, assuming the drawing is correct, the address of the configuration should be 0x20.
It appears that you have this right, but let me explain for those who may not be aware. The I2C address as used by the I2CDevice.Configuration is the 7-bit address. With some other interfaces for I2C, it is common to list two addresses for a device, one write address and one read address. The two addresses differ only in the lsb, where an even number is the write address and an odd number is the read. In the case of those interfaces, the address would be 0x40 for Write and 0x41 for Read.
This gets more confusing since some datasheets list the addresses as the Read/Write address, for instance Newhaven displays and the Sparkfun MPR121 use this method. In those cases to use the device you will often see

new I2CDevice.Configuration(ADDR >> 1, 100);

Second, according to the data sheet, when using the I2C device the speeds are 100kHz, 400kHz and 1.7 MHz so that is correct.

Now for the final point. I will admit that at this time I am just a compitent C# programmer. But I generally avoid using "var" when I know the data type. So, I would avoid using:

var setIOCON = I2CDevice.CreateWriteTransaction(new byte[] { IOCON, 0x24 }); 

instead I would have used:

I2CDevice.I2CTransaction setIOCON = I2CDevice.CreateWriteTransaction(new byte[] { IOCON, 0x24 }); 

Other than that I will see what I can do about duplicating you hardware and see if I can find something else.

After the modification to make the Joystick work with the Netduino the next step was to add some extra circuitry to support my next experiment. I wanted to control a servo or two with the joystick I also wanted some indication that the program was in control . So I added two 3 pin connectors for the servos and a LED. Here is an update to the schematic for the shield just incase someone want to critique it.

The biggest reason why AREF is not connected to 3.3V internally is because the SAM7X512 chip doesn't support that natively. The AVR chip on the Arduino has an "internal AREF" as an optional integrated feature.

The other reasons we didn't just wire 3.3V to AREF and skip the AREF pin: [a] we wanted people to be aware that the Netduino was a 3.3V device and to be careful not to put 5V into the analog pins when used in analog mode; [b] we wanted to maintain the chip's capability of having an AREF which varies from 2.7V to 3.3V...for our customers who are using Netduinos for commercial engineering prototypes.

That said, I've chatted with engineering about potentially adding an "internal AREF" option in hardware on a future Netduino board revision. It would be a cool feature to have, for sure. For now, connect the AREF pin header to the 3.3V pin header with a jumper wire when using analog inputs.

Chris

Personally, I like it the way it is. I was not confused by the AREF at all, my problem was that initially I did not pay attention to the fact that the shield had wired the pots to 5 vdc. Then in my haste to compensate I over drove the A/Ds by attaching AREF to 5V. Through this I learned a lot about the Netduino and its relationship to the Arduino. I won't make the same mistake again and hope that my original post will help others.
I conform strongly to the concept of modularity, therefore I feel that if the shield uses A/Ds then it is responsible for supplying the AREF. It may not matter much in the case of a connected shield, but having the A/D source supply the AREF is one sure way of insuring that the A/D's are reading accurately.
So my vote would be, If you are going to add "internal AREF" it should be done via a jumper on the Netduino and the jumper should be left off by default.
I plan to make all my projects supply the AREF for accuracy, so don't break my projects please.

Just a quick note for anyone who may want to use the SparkFun Electronics Joystick Shield, DEV-09760 http://www.sparkfun....oducts_id=9760. I bought mine to use for experiments with my Netduino. While it worked fine after I built it, I did find the there were problems with the analog reading for the X and Y pot on the joystick. Following the information I saw here I had added a patch wire from the 3.3 Vdc to Vref. But noticed that the center readings were 66% of full scale. which meant that the min to center would have twice the resolution of the center to max. I am a software engineer not a hardware engineer so it took me a full half hour to realize that the problem was that the pots were biased using 5 Vdc. I change the jumper for Vref to the 5 V source. This did a find job of centering the signal, but the max values were very unstable. I guess I was over driving the A/D. So I cut the trace from 5 V to the joystick and added a wire from 3.3 to the joystick and Vref. Now every thing works just fine. See the attachment.

What are the differences between SPI and the other thing that uses TX and RX? I understand that SPI has a clock so the shift register (lets use that as an example) knows when to read the other pin for a HIGH or LOW. but then how does the TX and RX communicate? how does it know when to get the data? Are they both Serial types of communication or not? Any info is appreciated, links are good too. Thanks!

Tx and Rx are used for Asynchronous Serial communication which is sometimes described as "self clocking". This is misleading to most users in that the data rate must generally be agreed upon before hand as Chris has stated, the selfclocking come from the method for detecting the begining of the data octet or byte. Here is the Wikkipedia page that describes this http://en.wikipedia....ver/transmitter as before I can only vouch for the correctness as of Jan 2, 2010 when I read it.

If I had a choice, I would use SPI over TX/RX because it is easier for me to use. If available and if the distance is not too great I would prefer I2C over SPI.

If available and if the distance is not too great I would prefer I2C over SPI.

Could you break this down a bit more? Distance being what? If I have a central Netduino in the house, and several scattered around the property, what's the prefered for 50 -200 ft, CAT5 cable?

I would not use I2C or SPI for those distances. In the first case, one should not think of I2C or SPI as a protocol for anything say outside the box. Both are intended for communication between ICs or small peripherals, like ethernet chips, lCD displays and the like.
If I have to go more than a couple of feet, then I would start to concider one of the interconnect serial protocols like Async (TTL, RS232, or RS485.)
Then if we are in the range of Room to Room or greater I would concider ethernet.
So in answer to you direct question. At 50-200ft, especially if you have already installed CAT5, go ethernet. The shields for 'duinos are cheap and .NETMF makes it easy to program.

What are the differences between SPI and the other thing that uses TX and RX? I understand that SPI has a clock so the shift register (lets use that as an example) knows when to read the other pin for a HIGH or LOW. but then how does the TX and RX communicate? how does it know when to get the data? Are they both Serial types of communication or not? Any info is appreciated, links are good too. Thanks!

I don't know how much time you have to read stuff, and we could spend a lot of time asking and answering questions so I thought that it may be helpful to supply you with a link to the Wikki page that describes SPI. This may be way more than you wanted to know but there are nuances to using SPI that are not immediately apparent and which many of us take for granted. So here is the Wikki link ( and yes I read it and it is a good description on Jan 2, 2010 You know how Wikkipedia can be )
http://en.wikipedia....l_Interface_Bus

Thank you for explaining now i understand. Time to play with my netduino!

The fun is just begining
The next thing you want to do is check out the projects page.

I just got my netduino and I'm starting to try to get analog input and I always get 0 when I read my pin(A0). Do you see anything I did wrong?

My setup looks like this

3.3->AREF

A0->Photo Resistor->GND

public class Program
    {
        public static void Main()
        {
            // write your code here
            InterruptPort tester = new InterruptPort(Pins.GPIO_PIN_A0, false, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeBoth);
            tester.Dispose();

            AnalogInput apin0 = new AnalogInput(Pins.GPIO_PIN_A0);
            apin0.SetRange(0, 100);

            int test = 0;
            while (true)
            {
                Thread.Sleep(250);
                test = apin0.Read();
                Debug.Print("Test: " + test);
            }

        }

    }

You would need another resister to 3.3Vdc to develop a voltage divider. There is no pull-up in the An-in.

My guess: CadSoft Eagle (?)

Yep, I use Cadsoft Eagle. But don't ask me for help with it. I am just returning to doing hardware after 40 years and am trying to catch up.I just kindof hack away with Eagle until something works.

I'm confused would it look like
AREF+3.3v->resistor(what resistance?)->ground?->photo resistor->A0?

First you need to know what the resistance of the photo resister is. Mine was 25k full dark.
Second you need to decide if you want it to pull-up or pull-down. I used mine in a pull-up.
Then choose a resitance to give you some kind of reasonable current limit, I chose 10K since I just wanted to play.
So using the attached schematic, I put the photoresister in a R1, a 10k in R2, you can try it either way and pick the one you like.

I found that when using the tactile miniswitches, http://www.sparkfun.com/products/97 , if I add a 0.1 mF cap from the signal line to gnd and enable the pull-up resistor cleans up the interupts just fine.

You can step the voltage all you want, but it will come as a cost of current. 6V probably would power the Netduino, not 100% on that though, I haven't looked at the schematics yet.

I have run the Netduino, and Parallax boe bot chassis on 4 AA batterys. ( 4 x 1.5 = 6Vdc)
I have been using the same batteries for over a week and had several test runs of the chassis. So I would say, 6VDC will just make it.
Remember you lose about 0.6-1.0 volts to a regulator and the Netduino wants a solid 3.3 Vdc for main power and 5Vdc +- 10% so your can get by.

Use a PWM. You can then control the brightness by changing the duty cycle (duration). I would reference the articles in this forum but you can't search for PWM or LED because of the search rules

As soon as I get the all-clear from our users that the new AnalogInput code in the v4.1.0.2 firmware patch is working well for them... It tested out well here, but I'm being extra cautious before I post a tutorial.

The tutorial should work well with the original firmware as well (since the patch only addresses using multiple AnalogInputs at once).

Chris

The new version is working for me so far. I am using it with the SparkFun Joystick shield. http://www.sparkfun....oducts_id=9760. This is the one I was having problems with on Sat.
Thanks for the update!

I unfortunately plugged my shield in off key without noticing it and when I powered my Netduino it failed to connect. I tried to find the software reason it wouldn't connect rather than what could be wrong with hardware. Once I notice the shield was not plugged in correctly, I disconnected the power removed the shield and allowed the duino to cool. TOO LATED Well live and learn. From now on, I won't power-up without checking the connections. Oh well now I have to order a new one Just had to get that off my chest.

I ALWAYS triple check my connections. So far, I have not fried even a single component.

I have gotten quite close though Just ask my temp sensor that had a backwards pinout to the dumb datasheet....

I guess I shouldn't try to work on my board with distractions. Just did not notice the pins that were not in their sockets.

Hi klotz,

No fun at all. It sounds like it got fried, but you may want to try erasing the Netduino (using the ERASE) pad and seeing if you can reprogram it. It's probably fried--but there's a small possibility of recovery...

Chris

P.S. Reverse power protection and a resettable fuse are built into the Netduino. And the odd pin spacing for shields helps keep pins in the right place. But while Netduino is designed to take a certain amount of abuse, it is possible to fry a pin (or in more extreme cases, to fry a whole Netduino). Most users will be fine--but it makes me sad to see one get electrocuted...

He's dead Chris.
No amount of protection can survive an unattentive user. Just got to excited about testing my two ethernet shields and didn't notice I had plugged it in wrong. The Seeeduino shield is wider than most so it is not as easy to see the pins if you don't pick it up and inspect it.
And of course I was convince I had checked it so I let it cook while I trouble shot the failure to connect. The Atmel was way hot, and I can't get any response from it at all except a very bad smell and lots of heat.
(Kind of reminds me of like Washington D.C. or Springfield, IL)
I'll mount this one on the wall with a note "CHECK THE SHIELD" hanging from it.
That's what overconfindence will get you.