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DrJaymz

Member Since 30 Dec 2011
Offline Last Active Oct 24 2012 09:04 PM
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Topics I've Started

PWM resolution

17 October 2012 - 08:53 PM

Does anyone know what the PWM resolution is when using 4.2? (Latest)? I am using PWM at 10Khz and the minimum duty ratio I can get is 0.01. Which suggests that the PWM resolution is 100. The ARM has a resolution of 16bit which is a good deal higher than the 7 bits I seem to be getting. This means when controlling LED brightness it goes from off to about 20% perceived brightness in one jump which is a bit rubbish really. I'm using Microsoft.Spot.Hardware.PWM, am I doing something stupid? Would I get a better result by setting the period and the duration of the pulse? I would have though this had already been posted but I couldn't find anything.

4.2 Confusion

14 October 2012 - 11:03 AM

Hi all, I have dusted off the netduino VMware system and aquired another netduino plus. I am confused because I cannot find a definitive guide to what I should be using with versions, the front page mentions 4.1 4.2 sdk, 4.2 firmware, 4.1.0 sdk for the plus and I can't figure out what I need. I have 4.2.0.0 RC4 firmware in my netduino and 4.2 SDK and latest netduino DSK but I cannot use the PWM because its all messed up and the checksums don't match and its all confused. So. Lets start over... Uninstall SDK's , Netduino and just have VS2010. Now, what to install and in what order? I'm happy to update the netduino firmware. Presumably even now, the bug where it cannot be reliably deployed is still with us?

How to determine how busy my netduino is?

19 March 2012 - 09:30 PM

Well my master piece is almost finished. Its got pressure transducers, accelerometer, thermopiles and LCD touch screen. Its a piece of avionics. Its awesome. Now, I have accelerometer, thermopile and pressure on a single I2C with some low-pass filtering. This all runs on a thread. My routines for the display use the UART and they also run on their own thread. Then my main execution runs on the main thread. I have logging on yet another thread. And I'm currently using about 38kb of program space. I was wondering if there was any way to determine the CPU load - I mean all those threads have thread.sleep in them at some point and if there is a speed limit my code hasn't reached it limited mainly by the speed of the display and the I2C devices. I was thinking of sticking GPS for ground speed and heading information on the spare com port. This will require constant baby sitting of the NMEA sentences. The question is will the little netduino cope? How to tell?

How much current can you draw from the 5v pin?

12 March 2012 - 10:39 PM

I'm using a serial qVGA graphic display that draws about 200+mA, the Netduino can draw a couple of hundred as well, sooner or later I often wonder if my issues with stuck deployment and general shakeyness could be lack of power. Also my project behaves differently when running from a USB charger as opposed to connected to a PC. The timings appear to change on the UART which should be fixed surely or else it wouldn't work properly.

Wonky Uart

02 March 2012 - 09:07 AM

I am having issues talking to a 4DLabs SGC display using the picaso serial interface. This is the issue. You talk to it at 9600 and then tell it you want 256k baud. It then changes and now you get 256k. The problem is that to change the baudrate on the netduino you need to close the port set the new rate and open it again. This causes a level change and results in the picaso interpreting that as a start bit and completely messing the whole thing up. I can prove that you need to close the port because the driver has a check for m_portopen and throws invalid operation if the port is open. Why is this the case, you can change the baudrate on just about anything else without having to do this? Surely its a case of updating the baudrate generator register and it should work - though I don't think that is possible from managed land. So, when the port is open the idle state is 1, when its closed is it 0 or floating? If it is floating then I can bodge it with a weak pull-up? Or perhaps anyone can tell me if they have closed and opened the port and it does in fact function at all after being closed? Its driving me up the wall because these are my last ideas, after which its probably game over for this project. That and the fact that I am really getting sick and tired of deployment failing after 4 or so deployments and then blue screening windows - make me wish I hadn't started with the netduino. Nobody seems to be able to fix it. If I find a solution to the 4dLabs I will remember to post it here as most people don't bother to update a forum when they fix something!

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