Curious if anyone has looked at the Raspberry Pi™ SBC? I've seen some talk about running NETMF on it, but don't know if anyone has taken the Linux compiled version of NETMF and tried it?

Sorry, I know this is not a NETDUINO related post, but I think there are some really smart and creative people on these forums... so what better place to ask.

I'm working on an audio project idea that I'm not sure could be accomplished with ND which is why I am looking at it.

I have been following the Raspberry PI with great interest. As you probably know, they are in extremely short supply and it will be a while (months) before most people can get their hands on one. Also the Raspberry PI has several features like USB host and HDMI video that would require drivers to work with NETMF. Since parts of the Raspberry By are not open source (particularly the Broadcomm chip used as the processor), I would expect the effort to develop drivers for all the hardware will be non-trivial.

In any case I am anxious to get mine, but to run Unix.

Anyone planning on attending the session Having fun with Netduino by Carl Bergenhem and Chris Gilmore this Saturday (29-OCT-2011) at the New England Code Camp in Waltham, Mass (USA)?

More info at: http://codecampboston.eventbrite.com/

You are quite correct that the hardware is quite capable of handling this frequency measurement task with ease.

The issue is the .Net Micro Framework. If you are willing to forgo .Net and program directly to the chip in C, you can get the job done.

What s not as simple or easy is to combine the use of .Net with native code and direct control of hardware interrupts etc. It may very well be possible, and I hope you succeed as we would all like this capability. You should be prepared for some setbacks along the way.

Can an Atmel AT91SAM7X512 microcontroller support the functions of the Taos TSL235R?

I am still not convinced that I need to throw more components at this problem. Netduino has an ARM7 48MHz processor- why should we deny that there is plenty of speed right on this development board? If I were to remove the processor from the Netduino and program it directly, or remove the .Net firmware and run C/C++ on it, I am sure that this sensor would run fine. I've read in these forums that version 4.1.2 of the Netduino firmware is supposed to offer run-time native code interop. I've also read about someone's project called "Fluent", which runs code something like 20 to 30 times faster than the managed code. I've also read that you can run FreeRTOS on the Netduino platform. Can't you run a quadrocopter with FreeRTOS? Isn't that real-time?

Does version Netduino 4.1.2 have runtime native code interop? If not, when will it have this functionality? Where can I get this "Fluent" project? Where can I find resources on how to run my own C/C++ on this board?

I understand the opinion that more tools will help me solve this problem, but I would rather use what I have instead of having to then deal with connecting, learning, and powering these other pieces.

Thanks,

Nick

As others have pointed out, a Netduino is not the right tool when you require precise real-time programming. There are however lots of cheap micro-controllers that can measure frequency and report the results to the Netduino via I2C or many other ways.

One cheap way to do this is with a TI MSP430 board which only costs $4.30 delivered (https://estore.ti.co...-kit-P2031.aspx ) This is probably the cheapest way to do a one-off project and the TI chip has reasonably good support.

The best way to look at this is that there is no one perfect single board computer. The key is to use one appropriate to the task and remember that they are cheap enough that you can break the task down and use more than one board.

IBM has contributed an open source implementation of the Paho, a simple protocol for sensor and machine to machine communication via the internet.

See:
http://www.adafruit....hings-protocol/

&

http://www.pcworld.c...ed_devices.html

This looks like a good way to get Netduinos communicating, has anyone used this Paho protocol?

Could you get a 1/4 inch audio jack and just stick it into the soil?

last night I was trying to work out a probe that reads the water level in my hydroponic window box. because the feed water is slightly saline, it conducts, so this approach will work great for it.

In my case, I want to read 'full' or 'empty', so I will just have two wires that are stripped at the ends, just above the low level.

I had thought about using resistance wire, with the water level forming a potentiomiter. that would allow a measure of depth.

thanks for the info!

One thing that is not clear from your question is if you are just trying to experiment or learn or if you are looking for a robust solution.

The reason I bring this up is because measuring full and empty with two wires that are stripped is cheap and easy but does not have good long term reliability. The first issue is that when a DC current passes through the probes electrolysis occurs and the wires degrade over time. One can use better probes such as platnum electrodes and use an AC rather than DC current etc.

On the other hand one can purchase for about $5 a MEMS sensor such as is used in washing machines to detect water level which outputs an analog voltage proportional to the water level. They are extremely reliable and will last practically for ever. I have used the ones from Freescale (http://www.freescale...et/MPXV4006.pdf ) for just this purpose. Take a look at the MPxx4006 family.

Currently I'm experimenting on a small scale using a window-box sized system. I'm in the process of building a greenhouse, and hope to automate it as much as possible, which is why I'm experimenting on the cheep now
For the full thing, I'll be building/buying sensors design for the long-term.

Thanks for the links! I actually have a pair or scrapped washing machines and a dishwasher, that I've been getting parts from as I need them. I'll see if I can find the sensor.

You might enjoy the video in this blog post: Plantduino Greenhouse Cares Of Your Plats While You’re Away In particular note how they use two ordinary nails to sense moisture in the ground.

All the details, parts list, schematic etc can be found at http://revoltlab.com/.

Here is a post you may find helpful: http://www.faludi.co...sensor-circuit/

Basically the way it works is that the resistance of wet soil is lower than that of dry soil. You could either make your own probe or hack one of the cheap probes from a garden supply shop.

JonnyBoats,
Thanks for the insight. So I guess reading the moisture content of something physical is slightly more of a challenge than originally thought. And that's because i can't find a sensor that will do that for me... But really isn't it the same idea as a pentiometer? One prong receiving electricity, another for it to exit, and one in the middle to read what's moving across the other two?

Very similar. It you would like to try a simple experiment you could stick two pieces of metal with wires attached into a pot of dirt. Connect one to the ground on the Netwuino and the second to one of the analog input pins. This second wire should also be connected to a resistor (try 1 MegOhm, value not critical) and the other end of the resistor to +3.3v on the Netduino. This is what is known as a pull-up resistor.

If the soil is bone dry then you should read a voltage of 3.3v (give or take) on the input pin, this is because the input pin is connected to v+ via the resistors and the resistance between the two pieces of metal is essentially infinite.

Now pour some tap water into the pot. The resistance between the two pieces of metal will now become some finite value and the voltage on the input pin will decrease.

If you were to immerse the two pieces of metal into a glass of salt water the resistance should become very low and the voltage on the input pin become close to zero.

The only real problem at this point is that the resistance also depends on the distance between the two pieces of metal in the dirt. If you wiggle the wires anc change the distance the reading will change as well. A "real" probe will be made so that the two pieces are held at a small fixed distance and usually combined into what looks like a single probe. In fact one connection is simply above the other, just like on a headphone plug that you would plug into the audio jack on your PC.

You can now buy a commercial probe if you like, and as with everything else the price will vary depending on who makes it and the required degree of accuracy.

There is one general trend that needs to be remembered, Moore's law. With virtually any computer, the one being announced and shipping next year will be faster and a better value than the one you bought last year. Comparing the Rasberry Pi to the Netduino is like comparing a PC to a Mac, the latest Mac is better than the original PC and the latest PC is better than the original Mac. If we think of a Netduino in general terms, that is a single board computer that runs the .Net MF, then surely there will be a newer version of the Netduino in the future with more memory, speed, I/O etc. Just think how great a Netduino with a couple of Gig of memory would be. You could fit the full .Net runtime in that! For me there are two key takeaways from all these single board computers: 1) They are advancing at a rapid rate with lots of newer, cheaper, more powerful ones coming out all the time. 2) These things are so cheap that it is easy to buy several to experiment and learn, there is no one perfect solution for everything. What a great time to be alive!

I was able to order five modules and a cable set from Amazon today, and am looking forward to getting this new stuff to play with. After all, one can never have too many Netduinos ;-) I see Chris posted a link to the documentation for the Netduino Go board here on the site. Could you also post the linked to the documentation for the various other components? Thanks.

A power sub-station with voltages measured in kilovolts and 1000s of Amps is really a special case where safety is paramount. As suggested in another response only properly designed industrial equipment tested and certified for such an environment should be used.

For others who might be considering measuring voltages in a residential location such as 120V or 240V (still lethal) there is a good "general" model to follow.

A Netduino (or any other micro-controller) is generally designed to operate on 5V or less (3.3V in the case of a Netduino). It is not designed to survive the application of high voltages (think of it this way, if it would kill you, it will kill a Netduino).

The best approach is to keep the high voltage (or current) on a separate board from the Netduino,

There are many Digital Multi-Meters (DMMs) out there which will output their readings on a serial port. The DMMs are designed and tested to be safe and reliable for measuring voltages and currents within their design specification. You can connect such a DMM to a Netduino via the serial interface (you may or may not need a level shifter such as a MAX232 but that is another issue).

Here is a post where someone used a DMM from Radio Shack in conjunction with a computer: http://www.linuxtoys.org/dvm/dvm.html The price they paid for the DMM seems high (old post perhaps?), I know I bought one on sale (different model) for about $30.

Have you considered measuring magnetic field?

Need a project (c#), in breadboard form to include the following:
2 Temperature/Humidity sensors.
1 RFID reader
1 Wifi
1 GPS
1-2 button(s)
1 display 16 x 2

We would all be glad to help you if you re-phrase your question, For example if you stated "I want to use a Netduino and would like to know what GPS, WiFi and Display shields work well with it?" I am sure you would get several well informed answers. As you probably know, shields simply plug into the Netduino (or Arduino for that matter) and generally are able to be stacked on upon another - no breadboard required.

Perhaps you are looking for a solution without any circuit boards? Did you mean you want to use a Netduino mini plugged directly into a breadboard along with other components? Your request is not clear.

Finally you do not state if this is intended as a "one off" project or a pre-production prototype. The reason I ask this is you should consider that there is already a readily available device that has:

RFID reader
Wifi
GPS
button
display

it is called a smartphone. All you would need to add is the two Temperature/Humidity sensors. Are you familiar with the Android Open Accessory Development Kit?

If you would like to discuss this further please send me a private message here on the forum and we can arrange to speak on the phone if you like.

The issue only has 2 votes on Codeplex! Go and Vote! (you might have to create an account)

http://netmf.codeplex.com/workitem/754

-Valkyrie-MT

I just made it 3.

With a new release of Fritzing (0.6.2) just released, I thought it would be a good time to bump this thread. I just downloaded the new release, and (like before) it is great to have all three variants of the Netduino in there "out of the box". A big thank you to those who made it possible.

I too find this sort of project fascinating. Thanks in advance for whatever details you choose to share with us.

You mean this one?

http://forums.netdui...4-game-console/

Yes, sorry. (It's still a great project though).

Fabien Royer did a nice blog post on his Netduino-powered Game Console at http://fabienroyer.w...d-game-console/

I too have the HelloPachube example running on a Netendo Plus powered by a wall-wart. It has been running continuously for a couple of weeks now. It runs fine and I can see the data on Pachube. I have definately had a few network hickups as well as outages lasting several minutes. The Netduino has not locked up once. As they say, your mileage may vary ..... Also a big thank you for your great book, I highly recommend it!

I see Arduino has announced several new products ( http://arduino.cc/bl...ast-at-arduino/ ) including a new Wi-Fi shield.

I wonder if it will be Netduino compatible??

Anyway they will have them at Makerfare in NYC this weekend, so perhaps someone can check them out.

I just ran across this excellent, simple guide to connecting external parts to a microcontroller: http://cq.cx/interface.pl#10

It is not Netduino specific, but would work with any microcontroller.

One caution, in his examples he often shows the voltage level as 5 volts, which would be fine for an Arduino or many other microtrollers. The Netduino is a Netduino is a 3.3 volt device so just replace 5 V with 3.3V in his drawings.

He describe how to:

Light an LED from a Digital Output
Read Switch Contacts with a Digital Input
Read a Digital Signal that Goes from 0 V (LOW) to 10 V (HIGH)
Read (with Opto-Isolation) A Digital Signal
Measure a DC Voltage Between 0 V and 15 V
Measure a DC Voltage Between -15 V and 15 V
Measure a DC Voltage Between 0 V and 1.7 V
Measure the Position of a Potentiometer
Measure an Unknown Resistance
Measure a Temperature
Output Characters on an LCD
Switch a 100 mA, 10 V Load
Switch a 1 A, 10 V Load That Always Stays Connected to Ground
Switch a 10 A, 40 V Load
Switch a 120 VAC Load

Tech Junkies just posted Open Source Robot Controls which uses a Netduino Plus. It is totally open source (hardware and software). The video is excellent and includes a walk-through of the Netduino code.

The code is far from 'perfect' but seems to work OK. There is one known issue. On rare occasions, the message string sent to the Netduino for setting the PWM has missing data. The Netduino will return a message informing you of the problem. To be blunt, I have no idea why, but at least it does not happen very often. I live near the BIG Chicago airport and I have issues with electronic items in the home at times. I 'think' it is from aircraft transmissions of some sort. Anyway, a plane is usually flying over and then have strange thing happen around here. Like hear voices on the TV and FM radio.

The usual way to handle situations like this, (namely sending data over noisy communications channels where the message can be garbled) is to include a checksum ( http://en.wikipedia.org/wiki/Checksum) with the message.

Basicly the sender computes the checksum and includes it with the message. The receiver then gets the message and re-computes the checksum to confirm that the computed value matches the checkum received. If they do not then the receiver knows the message has been corrupted and treats it accordingly. (One standard practice is to simply ask the sender to re-send the message).

This may or may not be overkill for your purposes.

This may be a wild and crazy idea, but why can't the waste heat from the LEDs be used in some way to heat the water in the aquarium? It just seems really wasteful to be cooling the LEDs at the same time as one is running a heater in the water. Some PCs are water cooled, is there any way to have a water cooled LED mount?