Argh! Point me to the unconfuzificator!

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I've been happily working with AVR's for some time now. Recently, I've decided that I should at least evaluate if the AVR32 UC3B's are a better choice for some of my applications.

So... I've been trying to do my homework -- looking over the literature and spending quality time reading the data sheet. Either I'm blind, ignorant, or both(*), but I find the UC3Bxxxx data sheet sorely lacking.

To be specific: The UC3B0's have three USART's, and the UC3B1's have two, according to the data sheet. OK, I'm cool with that. But I've been on an Easter egg hunt trying to find which one is left out of the B1's. The B0's do USB-OTG, the B1's only do device mode -- but the necessary I/O still seems to be brought to I/O pins. Same for USART's, the I/O seems to be brought through the mux... and that's just the stuff I *know* I don't understand.

Anyway, I am missing some big piece of this puzzle, or am overlooking something, or haven't found the right document yet.... or.... it's a secret only divulged over lunch with an FAE.

Anyway... please, somebody, whack me with a clue-stick. Where should I be looking?

-dave

(*) Don't ask my wife -- I have her opinion already.

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UC3B1 series comes in 48 pin packages only, while UC3B0 comes in 64 pin only.

Then look at section 11.8 in the datasheet (page 38).

Here you'll see package type, PIN number, GPIO number and then three peripheral functionalities per pin.

On UC3B1 you have RX and TX of USART0, USART1 and USART2 available on the pins. If you however need more than RX and TX, you might have less USARTs available on the UC3B1.

To select the peripheral on a GPIO line, take a look at section 20.5.3 and 20.5.4, here you see the register you need to write to for selecting which peripheral mux should be active on each I/O line. You also need to disable the GPIO feature on the I/O line, see section 20.5.2.

That should at least point you to where to seek information :)

Hans-Christian

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B0x and B1x have 3 usarts.

-sma

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Can either of you guys explain the table on page 3 then, that says there are only two USARTs? I *have* been studying the pin-out table. I can't reconcile that with the configuration summary on page 3.

Are you saying that the configuration summary on page 3 is under counting USART's because you can't have RTS/CTS on all three?

Also, what about the USB then? If I believe the pin mapping, then everything necessary for OTG should be available. But the configuration summary says device mode only USB.

The data sheet appears to be self-contradictory.

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Quote:
Can either of you guys explain the table on page 3 then, that says there are only two USARTs?

Simple: that's a datasheet typo :-)
Looking at the pinout you can see 3 usart are available in the 2 packages.

UC3B1x are USB device only, this is how the part is, and not related to the pinout.

-sma

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1K post! youhou :D

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sma wrote:
1K post! youhou :D

Cool. :wink:

-Deven

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Data sheet typo, marketing literature typo, device selection guide typo, web site typo... pretty darn consistent typo.

Are you saying they propagated the same mistake to a dozen places and the one place Atmel got it right is in a complex table that tries to describe two parts on a single page? I've been reading Atmel datasheets too long to believe that. (*)

I remain unconvinced. Every other place they tell me there are two USARTs on a UC3B1xxx. The data sheet has me confused enough that I'm not going to risk making a stack of green coasters.

-dave

(*) Just so nobody takes me wrong -- I'm not taking pot shots at the tech writers -- I've been on the other side of the data sheet, too -- errata happens.

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Contact avr32 at atmel dot com, they will give you the correct info.
-sma

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Well, I put in a support ticket at the Atmel web site with four questions about the AVR32UC3 data sheet -- they answered: one. Um, yeah.

Anyway:

Quote:
The available USARTs in UC3B1xx are USART1 and USART2.

Maybe if I ask them really simple questions, one question per e-mail, I can get this sorted out.

It seems that table 11-10 is really about UC3B0's, and we are left to guess which cells should be blanked out for UC3B1's. I will make an attempt to put together a readable, and with any luck, accurate table for UC3B1's and post it here. If anyone else can provide input, that would be most welcome.

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Thanks for the link. My forum searches hadn't turned up anything.

The linked thread makes sense as to why only 2 USARTs are practically usable. But, of course, Atmel just told me something that seems to imply that UART0 doesn't exist -- although it can certainly be read both ways.

The USB-OTG question still has me puzzled. I have another support request into Atmel about that. Also, I need to sit down and go through an I/O allocation and see if I turn up any other interesting conflicts.

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hehe, there is still 3 usart on B0 et B1 (even if one the B1 you will not be able to use the osc and the usart1).
There is no OTG function on the B1, this is function is not present and not usable (i have seen it so i can confirm it).

-sma

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In what way does the OTG function behave as not usable? The I/O pins are present in table 11-10. Does OTG simply not work, or does the USB peripheral present itelf to the software differently in some way?

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Quote:
In what way does the OTG function behave as not usable?

There is simply no OTG "feature" on the B1, so you can't use it. Check with Atmel support to confirm it.

-sma

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You don't understand my question. I'm not doubting that it isn't there. I'm wondering where the document describes exactly what isn't there. The combined document seems to be mainly a B0 document, with a cryptologic guessing game for B1's thrown in as a sick joke.

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Quote:
I'm not doubting that it isn't there

So contact Atmel, they will be able to tell you

-sma

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Just to close out this thread, I did get a more complete response from Atmel FAE's:

Quote:
... let me clarify the USART and OTG features on UC3B1.
USARTs:
You're right when you say the three USARTs are available on the pinout.
USART0-RXD: PA18
USART0-TXD: PA19
USART1-RXD: PA23
USART1-TXD: PA24
USART2-RXD: PA20
USART2-TXD: PA21
Problem with USART0 is that it shares pins with OSC0 and since OSC1 is not available on 48-pin package, USART0 becomes not usable since pins are used by crystal.
However USART0-TXD (PA19) may be usable in the case you use an external clock feeding XIN0 on PA18.

OTG:
The UC3B1 does not support OTG despite all signals are available on the pinout.
This is a hardware configuration and was initially a marketing configuration.

So the serial port mystery seems to be resolved.

It's not clear to me if the OTG is simply not hooked up but with all the host control stuff left in, or if host stuff is taken out, but it doesn't matter much either way.

-dave

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Sounds clear :)

-sma