Paul Newton's Content

#58397 Watchdog Reset Problem

Posted by Paul Newton on 26 May 2014 - 07:09 AM in Netduino Plus 2 (and Netduino Plus 1)

Hi Guido,

I have just looked at the Netduino plus V2 schematics.

The external reset appears to be an input only, I can see this because the /EXTERNAL_RESET signal is connected to the base of an NPN transistor. It can't act as an output, so it should not be affecting the reset chip.

Have you tried powering the reset chip from an external supply, whilst connected to the Netduino?

I am wondering whether the Netduino is affecting the 3.3V supply as it re-boots, causing the reset chip to give up.

On the schematic, the 3.3V on the header "+3V3_HEADER" appears to be connected to the 3.3V regulator via a transistor - it is controlled by a signal called "CTRL_OF_PWR_HEADERS" which is an output of the ARM chip.

The more I look, the more I think the power is being cut off when the ARM reboots. Also it looks quite hard to locate a place where you can access the unswitched 3.3V.

One place that looks like it might work, is the mini-jtag connector. This has +3.3V, Gnd, and /RESET pins. I guess that's perfect for a reset generator. If you were to modify the firmware, you might even be able to use one of the JTAG GPIO pins to send a don't reset signal to the reset chip using one of the other pads on the mini-jtag connector.

Hope this helps solve the problem - Paul

#58441 Watchdog Reset Problem

Posted by Paul Newton on 27 May 2014 - 08:17 PM in Netduino Plus 2 (and Netduino Plus 1)

Happy to help.

Would be great to see a picture.

Even better if you add a wiki page!

#60563 Silly problem with power over USB

Posted by Paul Newton on 28 October 2014 - 12:32 PM in Netduino Plus 2 (and Netduino Plus 1)

Hi Wernfried,

I think your USB port will not be able to supply enough current to drive the Netduino Plus 2 when active. The difference between the Netduino and a phone is that the phone has a battery that will smooth out the demand on the supply - e.g when the phone needs a higher current, the battery will supply it - the rest of the time the battery charges.

I was going to refer you to the Wiki page that has a comparison of Netduino boards, but the power supply figures for the Plus 2 are not in the table. However, looking at the Plus v1 in the table, it is listed as taking 80mA when active. The Plus 2 will be similar, so it is a safe bet that when your program turns on an LED, it could easily be taking the current consumption too high for the supply you have.

It might be better to take the power from the same supply that the router uses. Assuming the power goes into the router through a barrel connector, you could make a simple splitter using a plug and a pair of sockets, and pass the power to the barrel connector on the Netduino.

Hope this helps - Paul

#61554 set brightness for Room light

Posted by Paul Newton on 07 February 2015 - 02:08 PM in Netduino Plus 2 (and Netduino Plus 1)

Hi Seandy,

Welcome to the Forums.

The relay you gave a link to is not able to control current; it can only turn ON or OFF (100% or 0%).

You will need to find another type of module to control current.

Please be careful - mains voltages can and do kill people!

Try and choose a module that includes all of the high voltage components so that you only have to connect to a low voltage isolated input.

Have a search on the forums, I am sure others have posted with details of modules they have used.

Have (safe) fun - Paul

#60489 Servo position control

Posted by Paul Newton on 21 October 2014 - 06:20 AM in General Discussion

Hi Giuliano,

The simple way to do this would be to use a reed switch.

You wire it up just like a push button switch.

There are lots to chose from - different sizes, some with change over contacts.

In the UK Maplin have several around �2 to �4, this one being �1.99.

The only drawback will be accuracy.

The magnet will activate the reed from a distance, so it may be hard to resolve the position accurately.

If you need a really accurate position, then an Infra-red LED and transistor pair would be best, with the servo disc passing between the pair to block the light until a small drilled hole allows it through. The input to the Netduino would still be an on/off signal and the software should be the same.

I would start with the reed switch and get the system working first, then consider improving it.

Hope this helps - Paul

#61712 Pull Up, Pull Down, Pulling my hair out!

Posted by Paul Newton on 24 February 2015 - 09:02 PM in Netduino 2 (and Netduino 1)

Well done.

My first experience of I²C (not on a Netduino) was a very bad one. We spent around a week trying to debug our comms issue before we finally read the data sheet's errata list and found out the I²C would never work properly on the processor we were using. Then we had to work out how to make the product work without working I²C hardware - not fun!

Paul

#61672 Pull Up, Pull Down, Pulling my hair out!

Posted by Paul Newton on 20 February 2015 - 08:16 AM in Netduino 2 (and Netduino 1)

Just to confirm - return value of "0" means success?

What happens if you just add the resistors? (Pull-up to 3.3.V)

I would expect the return value to change to fail.

I'll have to get a hard hat.

#61677 Pull Up, Pull Down, Pulling my hair out!

Posted by Paul Newton on 20 February 2015 - 05:01 PM in Netduino 2 (and Netduino 1)

My knowledge has run out now.

There have been lots of threads about I2C on the forums, but I found that searching for them does not seem to work for me.

Perhaps someone else knows if the ACK is actually checked by the Netduino?

Maybe when writing, the ACK is not checked and the Netduino just counts the number of bytes sent out.

Anyone?

#61662 Pull Up, Pull Down, Pulling my hair out!

Posted by Paul Newton on 19 February 2015 - 07:28 PM in Netduino 2 (and Netduino 1)

I think there are a few of us from the Shire on the forums.

#61692 Pull Up, Pull Down, Pulling my hair out!

Posted by Paul Newton on 22 February 2015 - 07:39 PM in Netduino 2 (and Netduino 1)

Good to hear.

When you're done, the wiki is a good place to share.

#61655 Pull Up, Pull Down, Pulling my hair out!

Posted by Paul Newton on 19 February 2015 - 08:41 AM in Netduino 2 (and Netduino 1)

Hi IceMan,

I²C uses transistors to pull the signals to ground and pull up resistors to pull the signals up to the positive rail.

This allows the same two wires to send data in either direction, and you can have many nodes on the wires - e.g its a multi-drop system.

After each 8 bits, the sender listens for an ACK. An ACK is a low bit. If the pull-ups are not connected correctly, then it would be possible for the Netduino (the master) to hear a low bit for the ACK and assume it was the slave pulling the data line down. So your sends might be reported as successful.

This external page shows the waveform and talks about the signals in a down to earth way.

There is a Forum page about choosing the right voltage to pull-up to. I would pull-up to 3.3V unless your I2C device needs a 5V pull-up.

I think it would be worth initially adding the resistors with nothing else connected. Try sending something and verify the send now fails.

Then connect the two data lines and a ground to the slave device.

The slave will also need power, this may either come from the Netduino or a separate supply - as long as the grounds are joined.

Now try again and see if the send is reported as successful.

Take small steps and you should get there.

Have Fun - Paul

#60725 Problem with Pete Brown's post

Posted by Paul Newton on 16 November 2014 - 08:52 AM in General Discussion

I had the same issue, but was able to read the word of Pete by using the preview button.

If you hover your mouse between the title and the number of replies, a small button appears with a down arrow on it, click on it to reveal the post.

#58637 Problem driving DC Motor with HBridge

Posted by Paul Newton on 08 June 2014 - 01:40 PM in Netduino Plus 2 (and Netduino Plus 1)

We have all been there Ken!

Welcome to the Forums.

Paul

#59926 Powering EasyDriver and Netduino

Posted by Paul Newton on 28 August 2014 - 06:16 PM in Netduino Plus 2 (and Netduino Plus 1)

Hi Andre,

If the EasyDriver you are referring to is the SparkFun EasyDriver, then the A3967 IC on the board has built in protection diodes so that its internal transistors are not damaged by back emf.

You are right to worry about the motors affecting the Netduino. I was using a similar circuit with a 9V battery supply (6 x AA 1.5V) for my buggy and had to give up powering both from the same supply because the Netduino kept re-booting when the motors turned.

I was never aware of any damage to the Netduino - I think it was just brown outs, or maybe noise that was enough to trigger a reset..

If you are worried that the driver board will feed current back to the 12V supply, then add a rectifier diode in the positive line between the battery and the driver so it can only take current - that should protect the Netduino from high voltages.

(Note that the EasyDriver circuit does not have any protection for its own logic supply, so I don't think they are expecting any problems like this. However they do have a 30V tolerant input.)

You might also add a similar diode to the Netduino supply input and add a big capacitor after the diode so that short brown outs are less likely to reset the Netduino.

Let us know how you get on.

Have Fun - Paul

#60897 Obstacle Avoidance Robot with SeeedStudio Motor Shield V2

Posted by Paul Newton on 07 December 2014 - 09:14 AM in Project Showcase

Great project so far!

Mike is on the right track - we will need a wiring diagram to help understand what is wrong with the power.

The photos don't quite allow us to see the wiring well enough to understand what is connected where.

I use a mixture of fritzing and paint - both are free. Which one I select for a particular job depends on whether I think I will change the diagram a lot (in which case fritzing is better).

Have Fun - Paul

#58481 Netduino Plus Ethernet - Interrupt-driven libraries?

Posted by Paul Newton on 30 May 2014 - 06:17 AM in Netduino Plus 2 (and Netduino Plus 1)

I've almost completed the motor mount for the stepper motor for the turntable (needed two unusual-sized drill bits which I picked up this morning). After it's mounted, I can get serious about the programming portion.

I have been playing with some tiny RC servos to motorise my points (turn outs).

The board I have fits into the skirt under our living room table. The board has to be flush underneath - e.g. no solenoids or wires can stick out because people sitting at the table will hurt their legs!

I have located some very thin servos and found that I can use a router / multitool to cut a blind hole in the board under the points that the servo sits in. I added some folded aluminium to allow me to adjust the position of the servo and nail it in place when the point works well.

I found that using servos was actually cheaper than any thing else I could buy to achieve the same job. Now I need to actully fit to the board and work out how to route all the wires!

Paul

#61673 Netduino MiniSumo robot

Posted by Paul Newton on 20 February 2015 - 08:18 AM in Project Showcase

Great project!

#61541 LM35 & a PhotoCell

Posted by Paul Newton on 06 February 2015 - 08:13 PM in Netduino Plus 2 (and Netduino Plus 1)

Sounds a bit spooky.

I don't remember having issues with my analogue sensors.

(I am using three Sharp Infra-Red range sensors.)

Anyway, glad to hear you have a working solution.

Remember to have fun - Paul

#61527 LM35 & a PhotoCell

Posted by Paul Newton on 05 February 2015 - 05:02 PM in Netduino Plus 2 (and Netduino Plus 1)

Hi Cyn,

This is just a guess, but A5 and A4 are dual purpose (they are also I²C on the Plus v1).

Try using A0,A1,A2 & A3 (e.g LM35 on A3 and LDR on A0).

See if the problem has gone away.

I am not saying that you are using A4 & A5 as I²C - I am just wondering if they are behaving differently to the other analogue pins.

Paul

#61492 LM35 & a PhotoCell

Posted by Paul Newton on 03 February 2015 - 08:34 PM in Netduino Plus 2 (and Netduino Plus 1)

Hi CT1,

Tell us more about the "PhotoCell".

Is this a Light Dependant Resistor LDR or a solar cell that generates a voltage?

Either way, a link to a datasheet would be good.

If it is a solar cell, do you know the output voltage?

Is it possible you are driving too high a voltage into the analogue pin 0 ? (this could affect the ADC circuit in the Netduino)

Is the temp sensor affected if the cell is kept in the dark?

If it is a resistive sensor, how are you connecting it to the Netduino?

Have you used another resistor to form a voltage divider? Is the divider connected to 3.3V or 5V? (5V may be too high).

It might help to tie the other unused analogue inputs to ground each via a separate resistor - say something in the range 1K to 5K.

Lots of questions - hopefully one of them will provoke a eureka moment.

Paul

#62826 How to reduce pin usage

Posted by Paul Newton on 24 May 2015 - 07:13 AM in General Discussion

A nice thing about these serial to parallel chips is that all the outputs change at the same time. Individual GPIOs have to be changed one at a time.
Not always a problem, but sometimes important.
Paul

#61598 How do the input pins work ?

Posted by Paul Newton on 12 February 2015 - 01:49 PM in Netduino Plus 2 (and Netduino Plus 1)

Hi,

I am using a Netduino plus v1 with v4.2 firmware.

In C# I use:

using System;
using Microsoft.SPOT.Hardware;

InterruptPort port = new InterruptPort(pin, true, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeLow);

The mode at the end can be set to:

Port.InterruptMode.InterruptEdgeHigh, 
Port.InterruptMode.InterruptEdgeLow, 
Port.InterruptMode.InterruptEdgeBoth, 
Port.InterruptMode.InterruptEdgeLevelHigh, 
Port.InterruptMode.InterruptEdgeLevelLow

I think you are describing "Both"

Be aware that after the v4.1 to v4.2 firmware update, there are now two ways to configure inputs - Secret labs and Microsoft. So you may have issues using other people's code snippets unless you get the correct using statements and references. It had me confused for a while.

Hope this helps - Paul

#59707 GPIO Start Low

Posted by Paul Newton on 14 August 2014 - 05:45 AM in Netduino Plus 2 (and Netduino Plus 1)

Hi,

I solved this problem for my robot buggy by using opto-isolators.

I was using the Netduino Plus v1 whose pins are pulled high with weak pullups at reset.

These pullups were enough to activate the H-bridge circuit for my motors, but not enough to activate an opto-isolator's LED.

A single isolator was a small package so not a problem to fit into a small space, and they also make multiple devices.

The one I used was and still is �1.39 GBP in the UK from Maplin.

Its all written up on this WIki page: Driving high current / voltage loads.

Have fun - Paul

#60455 Continuous Rotation Servo

Posted by Paul Newton on 18 October 2014 - 08:00 PM in Netduino Plus 2 (and Netduino Plus 1)

Its always nice to here someone has followed my advice, but not as nice when it did not help. Just like being at work ;-)

Don't give up!

I think all the RC servos I have come across are designed for 5V, so a 9V battery is probably not a good idea as the extra volts could damage the electronics..

Also if you were thinking of a using a "PP3" 9V battery, be aware that these are intended for circuits that draw small amounts of current - like small radios, smoke alarms, etc. They are not really very good for supplying higher currents to motors.

I followed your link to the servo, you said it was a continuous rotation servo, I assumed you meant something that could drive a buggy wheel, but the link you gave is to a normal micro servo. I don't think it matters, but is it a continuous rotation one, or normal one?

Following the link, I am using some very similar servos to control some N-gauge model railway points (aka "turnouts" in American). They were small enough for me to fit into the base board of my layout without having to fit any hardware or wires under the board. The layout fits under a table - so nothing can stick out underneath as it will catch on peoples' legs when they are sitting at the table!

I found they worked OK for me as normal left - right servos.

We need to work out where the problem is - the Netduino/software or the servo.

Have you got any other servos you can use to verify the Netduino and software?

Or, have you got anything else that can drive the micro servo (maybe a radio control receiver, perhaps a friend has something)?

See if you can work out where the problem is.

It also might help to post your whole program or at least the bit that drives the servo.

Perhaps you could cut it right down to a tiny 10 to 15 line program or "test harness" that just drives the servo and demonstrates the problem.

You may have done something someone else will spot as being a problem. Maybe the servo class is being deleted by mistake after you use it.... There are lots of people on this forum, and when shown the right thing, they will solve the problem.

Hope this helps - Paul

#60399 Continuous Rotation Servo

Posted by Paul Newton on 12 October 2014 - 05:28 PM in Netduino Plus 2 (and Netduino Plus 1)

Hi Ludio,

How are you powering the servo?

When you say that it buzzed but did not move, it makes me think that there is not enough power for the servo to turn the motor, or there is not enough voltage for the analogue feedback circuit (in the servo) to work properly.

The ground and the PWM pins of the servo should connected to the Netduino, but the power should not be drawn from the Netduino.

Ideally, power the servo by taking a ground and +V to a separate battery pack.

Let us know how you get on.

Paul