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Old 27th April 2007, 09:58 PM   #1
Amdio is offline Amdio  United States
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Default I2c

Hi all,

I'm a newbie here so "Hi everyone!".

I had no idea there were so many geeks in one place. I count myself as adding to that number BTW.

Anyway, I found a nice little chip amp from National that has volume, bass and treble built in. They use it in monitors etc. with built in speakers.

I fancied making a headphone amp with it just for a giggle - I like traditional bass and treble and it would definitely be better than the iPod output into a pair of HD590s. I'm old, I like to be able to hear the music.

Trouble is that the bass and treble are addressable through I2C, which having dug into, doesn't look like it's easy to make happen. I'd just like simple push button controls (much like those found on monitors in fact) for volume, bass and treble.

Does anyone have any experience doing this kind of thing?

Thanks,

Moj
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Old 28th April 2007, 06:42 AM   #2
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Hi Amdio,

I write software for embedded systems for my sins/living.
Thankfully, early in my career, I had a brief encounter with I2C, that didn't go too well. Because of my misfortune, I have been able to avoid it ever since.

However, on a less defeatist point, I would suspect that some flavour of PIC would have an I2C port, so you could interrogate your push button inputs, use this as a basis to increment/decrement bass and treble settings, and use the I2S port to update this chip with the new values.

It can be done by wiggling IO lines in realtime to mimic I2S in the absence of a dedicated I2C port (this was what scared me away forever, so perhaps things have improved).

You'll need to be sure you know the I2C address of the destination chip, and make sure the I2C traces are fairly short, and not prone to interference.

Good luck. I'd be thinking of a different way to do this if it was me, but I'm a coward.

Cheers,
Phil
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Old 28th April 2007, 01:38 PM   #3
jcx is offline jcx  United States
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I also use MicroChip PIC processors, but starting from zero I would check out TI 430 developement system on a usb key chain frob for $20

http://www.ti.com/corp/docs/landing/...Other+OT+ez430
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Old 28th April 2007, 02:40 PM   #4
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I'd go with the PIC. It is widely available and still comes in the considerably more new user friendly DIL package.

An introduction to I2C. The target in question is a sprom but the general principles are well covered.
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Old 28th April 2007, 03:38 PM   #5
jcx is offline jcx  United States
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did you even look?

Click the image to open in full size.

a complete board with pcb pads is more convenient than a pdip, I'd say
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Old 28th April 2007, 07:34 PM   #6
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Originally posted by jcx
did you even look?

Seeing as I get regular emails from TI informing me of their latest and greatest widget, I was well aware of the promotion but more to the point why the confrontational attitude ? You made a suggestion, I made a suggestion as may others and presumably the OP will choose whatever seems appropriate. Didn't think it was a contest. What do you plan to do if someone has the temerity to disagree with you?
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Old 28th April 2007, 07:56 PM   #7
Amdio is offline Amdio  United States
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Thanks guys, that's some very useful stuff.

I think it' sa bit like trying to crack an egg with a pile driver but hey, that's what's called a challenge isn't it?

As for the did I look comment, um, yeah I looked quite a bit actually, what I didn't do was find. The key seems to be MCU, not I2C.

Thanks again!
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Old 28th April 2007, 08:11 PM   #8
guido is offline guido  Netherlands
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It's not that hard. if you would use a pic then there's enough on the net to get you going. And there's also code on the microchip website. Just remove all the stuff concerning more than one busmaster and that's it. No dedicated i2c port, just two of the i/o ports are enough.

If you never worked with controllers, a simple development board would be good.
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Old 28th April 2007, 11:24 PM   #9
jcx is offline jcx  United States
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the point about the ez430 is the low entry cost - $20 and some downloads and you should be able program it to talk to i2c - a couple of push-buttons and pull-up resistors would be all that you would have to wire

with MicroChip PICs I'm not aware of any similarly cheap dev system, yes you can download plans for building a programmer and proto up something on perf board but I call that a higher threshold

the Atmel AVR Butterfly eval board may also work for a similar price - and has a display

I would use a PIC but I know the chip and ins set and already own the tools, I wouldn't recommend them for a minimum startup time, minimum cost one shot project for someone without that PIC specific experience
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Old 29th April 2007, 12:05 AM   #10
jaycee is offline jaycee  United Kingdom
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Honestly, any microcontroller or microprocessor would do the job. The main trick is writing the software.

A lot of people recommend Microchip PIC's because they are cheap and easy to get programmers etc for. Personally I would recommend the Atmel AVR series because I find them more comfortable to write for. Honestly, you could use anything that's got some IO ports... any 8051, 68HC11, even an eZ80

The barrier to cross here is probably the software engineering required.
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