bill.french's Content

#5931 Netduino + SQL client (maybe System.Data.SqlClient)??

Posted by bill.french on 09 December 2010 - 02:34 AM in Netduino Plus 2 (and Netduino Plus 1)

$query="insert into tablename values('.$url1', '".$url2"', '".$url3"');";

I can't help but mention the risk of sql injection attacks -- unless i'm misunderstanding how php works, this appears ripe for that sort of exploit. Not that there's much risk when messing around with a netduino, i think establishing good habits regarding injection attacks early on before bad habits take hold are really important.

Here's some info in regards to php:
http://stackoverflow...njection-in-php

... and my favorite sql injection attack:
Posted Image

#5883 A First Project

Posted by bill.french on 07 December 2010 - 09:34 PM in Netduino Plus 2 (and Netduino Plus 1)

For temperature for a beginner, I imagine you'll start with a thermistor, check out this post: http://forums.netdui...ch__1#entry4703 -- You can replace the potentiometer with a thermistor; all of this stuff should be available at radio shack; what country are you in?

#5877 Netduino + SQL client (maybe System.Data.SqlClient)??

Posted by bill.french on 07 December 2010 - 08:23 PM in Netduino Plus 2 (and Netduino Plus 1)

I can't imagine sqlclient making it into the firmware... You could easily log to sql using an asp.net app or a forms app, you could look here for maybe a starting point: http://forums.netdui...ch__1#entry4637

#5875 Stepper Motor Control?

Posted by bill.french on 07 December 2010 - 07:57 PM in Netduino 2 (and Netduino 1)

The demo board is for a parallel port, I would go with the step genie and four of the mosfet things they recommend, assuming you have that type of stepper motor.. I've never driven a stepper so this is all guessing on my part.

#5874 Part Suggestions?

Posted by bill.french on 07 December 2010 - 07:55 PM in General Discussion

actually a netduino driven pinball machine would be a pretty cool project!! TO THE LAB!!

#5873 Part Suggestions?

Posted by bill.french on 07 December 2010 - 07:55 PM in General Discussion

my first instinct is to google pinball machine replacement parts, they tend to have lots of inexpensive solenoids...

#5867 Stepper Motor Control?

Posted by bill.french on 07 December 2010 - 06:04 PM in Netduino 2 (and Netduino 1)

I've added a step genie to my Christmas list: http://www.stepgenie.com/

#5796 Anyone have a clever hex->byte conversion routine?

Posted by bill.french on 06 December 2010 - 02:58 AM in Netduino 2 (and Netduino 1)

it doesn't appear that netmf supports int.Parse(hexValue, System.Globalization.NumberStyles.HexNumber); .. so does anyone have a clever hex to byte (or int or whatever) conversion routine handy, so that if I feed it the string "ff" it returns the number 255 in some form? Thanks!!

#5794 Serial Communication via D0 and D1

Posted by bill.french on 06 December 2010 - 02:50 AM in Netduino 2 (and Netduino 1)

OK I figured it out... I was receiving 4x more bytes than expected because the onewire->rs232 works in a completely unexpected way. Even once I disconnected the device, the uart still had data in it. So, when I ask it to read a byte, it returns the byte represented in hex using ascii characters... So, if I was expecting just this byte: 11111111 (in binary) (255 in decimal) (FF in hex) it actually sends the ascii character F twice followed by linefeed and carriage return, for a total of four bytes.

#5786 Serial Communication via D0 and D1

Posted by bill.french on 05 December 2010 - 10:58 PM in Netduino 2 (and Netduino 1)

I'm trying to get this onewire to rs232 device working, and of course it's not...

For serial, using D0 for RX (hooked to TX on my device) and D1 as TX (hooked to RX on my device), do I need anything other than:

var s1 = new SerialPort(SerialPorts.COM1, 9600);
s1.Open()

... and then I can read and write using s1.Read and s1.Write?

What does .Read do if there's no data there? Does it just wait? Return garbage?

I'm getting data via s1.Read with nothing even hooked up to the netduino.

#5664 What's the status of Onewire?

Posted by bill.french on 02 December 2010 - 08:18 PM in Netduino 2 (and Netduino 1)

My chips should come today, my sensor is due tomorrow, so i should have some news soon. I bet if you email him directly and ask him to just mail them, it should be much cheaper... otherwise, I can mail you one of mine once I get it going.

#5659 Pre-Assembled Kits

Posted by bill.french on 02 December 2010 - 07:26 PM in General Discussion

What, as an example, do you want pre-assembled?

#5615 What's the status of Onewire?

Posted by bill.french on 02 December 2010 - 01:48 AM in Netduino 2 (and Netduino 1)

Thank you, that is very good information, and I understand you perfectly. I ordered one of these: http://www.phanderso...mp/onewire.html It seems similar to your suggestions. I will let you know how it goes!

#5603 Proper LED Circuit

Posted by bill.french on 01 December 2010 - 07:30 PM in Netduino 2 (and Netduino 1)

Well, PNP is a totally different animal. My circuit assumed the more common NPN style transistor.

From: http://www.kpsec.fre...om/trancirc.htm

Posted Image

#5595 Proper LED Circuit

Posted by bill.french on 01 December 2010 - 05:21 PM in Netduino 2 (and Netduino 1)

You got it working with a motor as I remember -- have you substituted the motor with an LED, now? It should work, assuming you have the LED oriented properly? I would start using any output port, such as D0, which is the most upper-right pin on the netduino. Once you get it working, then move on to PWM. I see you are in NYC, do you have a car? I'm joining a hackerspace in Highland Park, NJ, which is about 1/2 way from NYC, id be happy to get together and work on some stuff. Your previous thread: http://forums.netdui...ch__1#entry4823

#5590 Proper LED Circuit

Posted by bill.french on 01 December 2010 - 03:52 PM in Netduino 2 (and Netduino 1)

I just attach LEDs to a digital i/o and then a ground pin, but I still need to get a breadboard. Maybe that's not the way with a 10mm one.

You're probably "ok" doing this, but not too many LEDs draw less than 8ma, so you are theoretically risking running outside of the specs and burning out your netduino, if you are using one of the 8ma or 16ma pins. You should probably use some kind of resistor, regardless.

#5584 Proper LED Circuit

Posted by bill.french on 01 December 2010 - 02:44 PM in Netduino 2 (and Netduino 1)

also, i just realized, the OP was using a 10mm 3.5-4v LED, which is higher than the 3.3v of the outputs, so my circuit should probably have the collector side hooked to 5v instead of 3.3v.

#5583 Proper LED Circuit

Posted by bill.french on 01 December 2010 - 02:41 PM in Netduino 2 (and Netduino 1)

The specs of the netduino: max current: 8 mA per pin digital pins 2, 3, 7: 16 mA per pin analog pins 0-3: 2 mA per pin microcontroller max current: 200 mA total 8ma and 16ma are a little "low" for driving many LEDs.. the "standard" i remember from way back for LEDs is 21ma, but there are many different leds out there, and some are much brighter and draw much more current. So, to avoid burning out your netduino's pins, you should probably use a transistor. (certainly I and others have been driving leds directly, but...) Also, this kind of circuit is an easy way to learn about transistors, and with an added diode for safety you can drive motors, relays, etc.

#5581 Proper LED Circuit

Posted by bill.french on 01 December 2010 - 02:32 PM in Netduino 2 (and Netduino 1)

Also, in addition to what Fred said, I generally like to have the "load" on the collector side of the transistor, otherwise the load gets involved in the base-emitter current, which can complicate things. So, now with an extra resistor, and the load on the collector side, a diagram:

Posted Image

I would use a 1k transistor to the base, which (using V=IR) works out to a safe 3.3ma (I=V/R, or I_B = 3.3v/1000, which is .0033 amps, which is 3.3ma) current from the netduino pin, and a 220k resistor for the LED load, limiting the current to 15ma (I_C = 3.3v/220) which should be safe for most leds, but possibly a little dim. (Check your LED specs)

#5508 What's the status of Onewire?

Posted by bill.french on 30 November 2010 - 01:20 AM in Netduino 2 (and Netduino 1)

Any suggestions on a chip? I'm having trouble finding anything. Closest I could find was this: DS2480B but DIP would be much easier for me. Thanks!

#5504 What's the status of Onewire?

Posted by bill.french on 29 November 2010 - 11:23 PM in Netduino 2 (and Netduino 1)

Hello! I ordered some DS18B20 temperature sensors, before I realized I had no idea how to interface them with the netduino -- what's the status of onewire? What do i need to do to support onewire and interface with the DS18B20? Thanks!

#5460 12-Bit ADC Measurement using MCP320X chips and SPI

Posted by bill.french on 28 November 2010 - 02:33 PM in Project Showcase

If you don't mind me asking, what kind of project are you working on?

#5453 Reading a photoresistor

Posted by bill.french on 28 November 2010 - 01:02 PM in Netduino 2 (and Netduino 1)

Any way you can post a photo? Seems like it should work, although the analog inputs only support 3.3v, so maybe you're outside of that with the 5v connection. My other guess is that you're not feeding 3.3v to the aref pin. This link might be helpful: http://forums.netdui...ch__1#entry4703

#5405 12-Bit ADC Measurement using MCP320X chips and SPI

Posted by bill.french on 27 November 2010 - 02:19 PM in Project Showcase

Thanks for this, I have been playing with an MCP3204 -- i was wondering the "proper" way to combine the two bytes into the reading.. bitwise operators have always been mysterious to me. I got it working but my solution does not look nearly as smart as yours...

I have been having a ton of problems getting decent, stable readings, though. Do you have any sample circuits and pictures you could post?

Here are some premade boards i've been thinking about:
http://www.mikroe.co.../easyadc-board/
http://www.mikroe.co...dc-proto-board/

Posted Image

#5403 Anyone have a Windows Phone already?

Posted by bill.french on 27 November 2010 - 02:09 PM in General Discussion

Well, I think it's a great idea. I probably won't get a windows phone any time soon, simply because i'm still mad at how terrible pocket IE was all the way up through window mobile 6.5 ... I mean, it's like they were intentionally being cruel to the users -- but if I saw something cool going on with visual studio, c#, and a netduino plus, i could be swayed. I mean, my droid is nearly a year old now, if you can imagine someone keeping a phone for so long!

By content type

See this member's