Just for fun

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Oh-man :roll:

Some day I get REALLY carried out. This started as a very simple GSM thingy that would have two DAC:s in order to make it speak back to You. SMS messages are so booooring...

What I ended up is something else. IMHO this is walking along the very thin line between sane and insane. Hopefully on the sane side.

How to check this out before starting the PCB design ?

Well - I just thought that maybe You could do it ;)

I have put aside 30 Atmega32L-8AI controllers. You will get one controller for each error You find. as long as there are controllers left from this 30 controller bunch. I will pay the postage. (this is the reason I chose the SMD version of the controller).

I am a sloppy man so there are good chances that all these controllers are already gone.

Edit: I already found one - and it is a show stopper. So at leas one chance to get a free Atmel....

Attachment(s): 

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How about that picture of Britney? Isn't that an error?

Chuck Baird

"I wish I were dumber so I could be more certain about my opinions. It looks fun." -- Scott Adams

http://www.cbaird.org

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What - She's perfect. With beard and all.

However - never asked Britney - she might have an alternative opinion.

Hint: The error is around IC6.....

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Hi Eskoilola,

Nicely drawn schematic.

I like the slow turn on power supply. At least at first glance I think that is what will happen.

I was surprised that the mic and speaker DACs feeding your DC bias offset are Cap-Cap coupled. I expected to see them RC (filter) coupled to the DC bias divider.

I'm still trying to sort out IC6 signals and trying to guarantee no signal contention.

Only your data sheet will reviel whether or not your GSM reset and boot signals need pull ups on the board, (which are not currently present).

I'll have to take another look or two.

It looks like a fun project!

JC

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I don't see a resistor from mega32.RX to '+'.
George.

edit: I notice you want to set the volume to the amplifier with a PWM through a latch. Will not be very comfortable from a software point of view as you have some devices on the data bus.

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eskoilola wrote:
Hint: The error is around IC6.....
Esko,

If you'd stop using these outrageous ISO symbols which only overwhelm you with unnecessary information, (and perhaps split the schematics into groups fitting nicely onto a single screen or an A4), you'd immediately see that you swapped the data and gate inputs on the '125... OK, that was using the hint. I am not going to go any further as it takes me too much time to scroll up and down that huge sheet.

Jan Waclawek

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Sorry, no chance to view this huge sheet.

I would suggest to divide it in readable subsheets.
I prefer A4 size on my projects.

Peter

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angelu wrote:
I notice you want to set the volume to the amplifier with a PWM through a latch. Will not be very comfortable from a software point of view as you have some devices on the data bus.

Actually - it is not volume control - it is mute. It is there to keep the loudspeaker silent when not needed. The volume control is done by scaling the DAC values and by controlling the WMOi3

The resistor from AVR Rx to VCC is not actually needed since IC6-A and IC6-B are not in 3-state mode at the same time.

Nevertheless - there is a short period of time when neither is steering and another when both are steering. Resistor there will be. 1 Atmel for You.

wek wrote:
you'd immediately see that you swapped the data and gate inputs on the '125...

That's another Atmel for You.

Please PM You addresses to me so I put the envelopes on the sway.

wek and danni wrote:
....outrageous ISO symbols.....
....Sorry, no chance to view this huge sheet....

Now, whether the sheet is big or not depends mostly on what sort of display You are using. I agree that it is way too big to be viewed on my laptop. On my hobby computer I have a display that has enough surface to view that schematic and still have room for tools and so on.

Now - if I would compress it down to "normal" 150 dots / inch (it is now 300) some of the symbols would be clobbered. I consider that being the worse sin of these two.

Still point taken - splitting it down is doable - just have to rearrange it in a way that the buses and only the buses cross the page boundaries.

The outrageous ISO symbols are actually not ISO... ;) I have designed them for easy swapping of ports in a logic array. This is because I start designing the PCB already at this stage. Note the address pins on the SRAM ? They are all "f****d up" - but when You place the latches and the SRAM on pcb You notice that there is a certain reason for this.

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Quote:
The resistor from AVR Rx to VCC is not actually needed since IC6-A and IC6-B are not in 3-state mode at the same time.

Yes they are, and this happen when you communicate with the MAX232 and the MAX232 Rx state line is high. It is not a conflict outputs actually, but the AVR Rx line will be not activated HIGH properly.
I think IC6.5 and IC6.6 are reversed.
Anyway, if you intend however to install the resistor, great.

Quote:
Actually - it is not volume control - it is mute. It is there to keep the loudspeaker silent when not needed. The volume control is done by scaling the DAC values and by controlling the WMOi3

Scaling an 8bit signal will reduce the accuracy. But duable however.
George.

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None of the polarized caps show the polarity, and there are a lot of 4-way junctions in the schematic. Otherwise, I don't see any real issues.
/mike

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n1ist wrote:
None of the polarized caps show the polarity, and there are a lot of 4-way junctions in the schematic. Otherwise, I don't see any real issues.
/mike

Actually - polarized caps are really scarce on this schematic. Those are showing polarity. You can find them on the regulator chain and on the audio power amplifier.

Rest of the caps are either ceramic chip or plastic or radial ceramic disc (rectifier spike suppression).

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My mistake - I guessed that caps specified as 1/25 or 10/6 were tants with a voltage rating (and forgot about the different polcap symbol that the rest of the world uses :-) ).