Stefan W.'s Content

#20485 Inconsistent reads on ultrasonic range sensor?

Posted by Stefan W. on 11 November 2011 - 01:58 PM in Netduino 2 (and Netduino 1)

The busy-loop method is not very accurate as a single read can take pretty long - i've used an InterruptPort to detect the edges (you'll need another port or some piece of circuitry with e.g. a 555 to trigger the sensor reading, since there's no tristate for interrupt ports ...). Mario, it's at http://www.seeedstud...surement_module - it's basically the same as the Parallax Ping))) which already has some threads here.

#20443 How to glow 2 or more LED ? on LEdhtmlControl program

Posted by Stefan W. on 10 November 2011 - 08:30 AM in Netduino Plus 2 (and Netduino Plus 1)

How did you try modifying it? Can you post the code you tried, and show how you connected the LEDs to the netduino?

#20395 Deploy over TCP/IP

Posted by Stefan W. on 08 November 2011 - 11:38 PM in Netduino Plus 2 (and Netduino Plus 1)

The TCP/IP-Bootloader is too big, that is why it is not included in the netduino+.

#20334 Wifi Temperature/Humidity Help?

Posted by Stefan W. on 07 November 2011 - 11:38 PM in General Discussion

That particular sensor asks for a 4.5V or up supply though, so you'll have no luck feeding it from a regulator that gets its input from USB ... so either add filtering or use another sensor.

#20333 DS1307 Sparkfun I2C

Posted by Stefan W. on 07 November 2011 - 11:37 PM in Netduino 2 (and Netduino 1)

Arduinos I2C library uses the internal pullups of the microcontroller when it's not driving the line low - those are weak pullups, but since it only uses "slow" I2C, it works most of the time ... that's the reason you didn't need it, it's still better if you do have external pullups there.

#20257 Frequency counting and trying to understand what i'm actually doing

Posted by Stefan W. on 05 November 2011 - 04:47 AM in Netduino Plus 2 (and Netduino Plus 1)

You don't need the port.ClearInterrupt(); for edge triggers. Also, I'd use two numbers, one for storing the last valid result and one for counting, so your result stays valid during counting ... also, your class lacks a method for an outsider to read the counter

I would have thought that increasing humidity would increase the frequency.

Increasing humidity increases the capacity of the sensor, and since the time constant of RC circuits is - well - R times C, the time constant increases when C increases. Longer time -> lower frequency.

Edit: forgot to say - so when you want something that scales with humidity, use 1/count (times some constant that you have to determine through calibration).

#20249 Frequency counting and trying to understand what i'm actually doing

Posted by Stefan W. on 04 November 2011 - 09:41 PM in Netduino Plus 2 (and Netduino Plus 1)

I guess you are referring to the method detailed using the 74hc4060. You can either build a loop that polls the input repeatedly for several seconds and count the number of high-low transitions (or low-high, does not matter), or use an InterruptPort and generate interrupts for each transition, enabling your netduino to do something else while you're counting.

#20246 RS485

Posted by Stefan W. on 04 November 2011 - 09:11 PM in General Discussion

Regarding "native to the netduino" - you'll need a level shifter like the max232 (cheap IC) to convert the signal levels from standard RS232 levels to 3.3V levels. That document does tell you how to send the data, and the timing seems to be forgiving, so that should work out.

#20245 Arm DSO Nano and family

Posted by Stefan W. on 04 November 2011 - 09:11 PM in General Discussion

PWM generated by netduino (max freq 500 khz), yes. Ethernet communication will be too high frequeny, i fear.

#20237 RS485

Posted by Stefan W. on 04 November 2011 - 06:07 PM in General Discussion

You will need some intermediary hardware, because of the symmetric data transmission (the signal is the voltage difference of the both signal cables) and - as far as i can see - +- 12V data transmission (netduino uses +3.3V/Ground). I haven't seen any protocol description at a quick glance, so i don't know if there's further barriers there ...

#20189 Why does the SPI library only have WriteRead()?

Posted by Stefan W. on 03 November 2011 - 11:14 PM in Netduino 2 (and Netduino 1)

Well, if you don't connect MOSI (the line where you send the data), then it literally does not matter what you send

Also, be sure to get the headers for the arduino if you want to use it as a shield, it seems the "shield" does not come with them (so you'd have to solder wires or connectors to them).

#20175 High Speed Flash Photography

Posted by Stefan W. on 03 November 2011 - 06:36 PM in General Discussion

Oh ok, thanks for the quick reply. I would probably like to focus more on water droplets photography for this project. Timing perfectly two drop of water so that they collide in an interesting way and then trigger a flash to free the moment in a picture.

I did some research and this arduino shield already exist with a bunch of accessories available that we can buy like water valves, camera trigger cables various triggers like laser sensors, sound sensor etc. Do you think this shield would be compatible with netduino?

Thanks,

If you show it here, we could probably tell you - there's nothing in principle saying it can't, it's always in the details (about power supply, voltage levels, communication ...).

#20148 Arm DSO Nano and family

Posted by Stefan W. on 03 November 2011 - 09:39 AM in General Discussion

I measured the actual bandwidth, and it's 2-3MHz: it means a typical SPI signal is yet distorted;

I'm not an expert on scopes (just a user ...), but doesn't that mean that the infos on http://iteadstudio.c...products_id=355 are very off? (It claims to have an analog bandwidth of 72Mhz and up to 72MS/s (well, it is odd that those numbers are the same) - that is an order of magnitude off ...)

#20125 TLC5940 PWM Driver

Posted by Stefan W. on 03 November 2011 - 01:42 AM in Project Showcase

Hey Mark,

Got all the bits now I think... for the less able of us in regards wiring things up is there any chance you could perhaps fritz the tlc with the oscillator so it is possible to easily reproduce this?

PS hows the daisy chaining going on? And is it possible to reduce the number of netduino pins used (I refer to pins 8,9,10 in your code) for example can you provide high and low logic from a shift register such as stefans bit shift example?

Thanks

Andy

If you feel it's above you to easily reproduce the circuit, you could use another clock source. I think you should be able to use http://www.sparkfun.com/products/9116 for this, the two clock outputs should suffice to create the clock and the blanking signal.

#20095 encode.utf8 problem

Posted by Stefan W. on 02 November 2011 - 09:36 AM in Netduino Plus 2 (and Netduino Plus 1)

To elaborate further on that: There is no way to read a fixed number of bytes and then decode this as UTF-8, you might always end up in the middle of a codepoint. If the file is too big to fit in memory whole, you could, if the lines have a maximum size that fits in memory, do as CW2 says and read until end-of-line (assuming they use \n for end-of-line and not the more elaborate unicode line/page breaks

) and decode the line, which will work since the "usual" end-of-line character is a single byte, or you really have to buffer and specifically look for codepoint boundaries.

#19998 Nokia 5110 LCD & 74hc595 on SPI?

Posted by Stefan W. on 30 October 2011 - 12:10 PM in Netduino Plus 2 (and Netduino Plus 1)

Just to add: the bug occurs when you try to use pin 4 as a chip select pin, not when you try to use it as a GPIO, so as a GPIO you're fine with pin 4.

#19965 Nokia 5110 LCD & 74hc595 on SPI?

Posted by Stefan W. on 29 October 2011 - 03:44 PM in Netduino Plus 2 (and Netduino Plus 1)

technically, the "latch pin" is something different than a "chip select" pin, and the usage as chip select is not quite correct - you'll notice that when you don't make full writes to the shift register (the shift registers still use the clock and data inputs even when you don't write to it, so if you don't use full writes on the shift registers you'll see garbage - if you always write all bits in the shift registers you won't notice).

#19940 Code fails when battery powered.

Posted by Stefan W. on 28 October 2011 - 09:24 PM in General Discussion

7.2V is below the specs - the netduino asks for at least 7.5V as unregulated input (which means in case of battery you should aim for more since the voltage drops as the battery discharges). This might be the cause for your stability issues ...

#19917 Netduino + LinkSprite JPEG Camera

Posted by Stefan W. on 28 October 2011 - 11:59 AM in Netduino 2 (and Netduino 1)

Don't know if it's the same, but http://code.tinyclr....camera-library/ looks similar.

#19889 Best way to do this?

Posted by Stefan W. on 27 October 2011 - 09:39 PM in Netduino Mini

By not using a resistor you might let your mini become hot, and it doesn't like that

(as RichardE said) - You might want to have a look at http://www.kpsec.fre...trancirc.htm#ic which tells you about how to choose the transistor/resistor values. There's also other interesting things on that page

#19867 I become crazy because wiring?

Posted by Stefan W. on 27 October 2011 - 04:11 PM in Netduino 2 (and Netduino 1)

You still have the wiring wrong. You have Netduino Pin 13 = MOSI connected to 595 Pin 11 = Shift register clock with the blue cable, and Netduino Pin 11 = SPCK goes to 595 Pin 14 = Data serial (pink cable). Switch the blue and the pink cable at the netduino.

#19863 Best way to do this?

Posted by Stefan W. on 27 October 2011 - 12:30 PM in Netduino Mini

The IC probably does not fulfill the "I should be able to get the missing parts before friday", that's why I just put it in as a joke

There are also other chips that talk over I2C and save one more pin, if that's really an issue.

#19831 Nokia LCD + Arduino Ethernet Shield not working (together)

Posted by Stefan W. on 27 October 2011 - 12:52 AM in Netduino 2 (and Netduino 1)

I used neither - but just as an outside guess, if both use SPI, what you're passing there is probably the chip select pin, and that should be different for those - so wire it to another pin for one of those, and adjust the source (use any pin but not pin 4). Both using the same SPI module is not a problem ...

#19825 Using the switch

Posted by Stefan W. on 26 October 2011 - 08:30 PM in Netduino Plus 2 (and Netduino Plus 1)

The reset is automatically disabled when you use Pins.ONBOARD_SW1 as an InputPort or InterruptPort, nothing you have to do in addition to that - the netduino is nice like that

#19821 Best way to do this?

Posted by Stefan W. on 26 October 2011 - 03:56 PM in Netduino Mini

With the antiparallel LEDs, you need 2 pins per pair -> one pin per LED -> 5 total, your fritzing board uses 6 pins for 4 leds

- if you use a shift register + transistor, that'll be 4 pins (clock, latch, data + transistor), where you can't individually control the brightness ... if that's ok for you, you could do that - or just use an LED PWM driver IC

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