Jack Gassett

Analog Write

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2010-12-05 11:38:30 [Arduino] analogWrite

Posted By: Jose M. Alcérreca

Join Date: 2010-12-04

Location: SPAIN

Message ID: 86

Hi,

This is my first post here. I've just received my Papilio Platform and it is a great piece of hw.

Arduino will be the starting point of most of the people to this platform so that's why I want to help improving the compatibility between the two.

First of all, analogWrite is not yet implemented. I guess this is due to the fact that timers are always a big pain :)

Before I start, is anybody working on it?

Thanks.

Jose.

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2010-12-06 10:23:19 Re: [Arduino] analogWrite

Posted By: Jack Gassett

Join Date: 2009-02-18

Location: UNITED STATES

Message ID: 87

Hello Jose,

The FPGA pins do not directly support Analog but there are two approches we can take to get analog working. One method is to use the SPI Wing for a SPI ADC solution:

The other method is to use a Delta-Sigma DAC and a minimal hardware for Analog functionality as outlined in these two Xilinx Apps:

http://www.xilinx.com/support/documentation/application_notes/xapp154.pdf

http://www.xilinx.com/support/documentation/application_notes/xapp155.pdf

On another note, I setup a nicer SMF based forum system. People were complaining about this GFORGE Forum system being to difficult to find things in. Each project has its own forum and it makes it hard for someone to easily identify the best place to put their post. In order to keep this thread from getting lost I'm going to move it over to the SMF forum. In a couple days I'm going to shut this GFORGE forum page down.

Jack.

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Ok, I'm with you then. Implementing a PWM module that is controlled in with the same registers and behaves in the same way as the Analog output functionality of the Arduino/AVR sounds like a good idea. I don't think it would require any external components either...

I think the advantage of the Delta-sigma and the external resistor for the Analog output functionality is that you can change the voltage at much higher speeds than you can with PWM. But there are many, many applications that do not need the output voltage to change at a high rate of speed. So a PWM output is probably the best solution.

Jack.

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Guest pepevi

Also, in order to achieve total compatibility with Arduino, I think it should be PWM.

A/D conversion with Arduino should also be discussed in the future in order to make analogRead work seamlessly with the ADC Wing.

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