AVR32 vs STM32: Toe to toe...

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We are looking at a new development using a 32-bitter with a small RTOS (not linux :? :D ) in a terminal-type application. The current favorite part is the new STM32 cortex part from ST. I'm an AVR fan and to me the AVR32 part would be a good candidate - what are the panels arguements for and against :D

-=mike=-

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You say little about what you need of peripheral, but I guess the uC3A and uC3B should suite your application nice.

They can run FreeRTOS or ThreadX, depending if you want to go open source or buy something :)

Hans-Christian

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According to both datasheets:

1/ STM32F103
48MHz - 33mA (running in RAM, even not in flash: add 1waitstate above 24Mhz, and 2 waitstate above 48MHz, this would even lower the DMIPS/MHz ratio).
60 DMIPS@48MHz

2/ UC3B
50Mhz - 19.5mA (running from flash)
65.5 DMIPS@48MHz

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Jokerman wrote:
We are looking at a new development using a 32-bitter with a small RTOS (not linux :? :D ) in a terminal-type application. The current favorite part is the new STM32 cortex part from ST. I'm an AVR fan and to me the AVR32 part would be a good candidate - what are the panels arguements for and against :D

-=mike=-

I would say the STM32 is more of a very low power optimized processor, capable of running at very low speeds at low power, the standby current is a few uamps vs the AVR32 40uamps or so. So if you running at 1Mhz the STM32 is probably a better choice, if on the other hand you running at full speed all the time and don't need any special low power modes, then AVR32 is better. The STM32 is cheaper, but doesn't have the large RAM options the AVR32 has.

The STM32 is a ARM based processor, which is nice.

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joepierson wrote:
I would say the STM32 is more of a very low power optimized processor, capable of running at very low speeds at low power, the standby current is a few uamps vs the AVR32 40uamps or so.
The UC3 is optimized for power too, static sleep modes are down at 4uA (admittedly the STM32 can get down to 2uA but when you're this low you godda ask yourself just how much you care ;) ).
joepierson wrote:
So if you running at 1Mhz the STM32 is probably a better choice, if on the other hand you running at full speed all the time and don't need any special low power modes, then AVR32 is better.
I'd might actually lean the other way, the STM32's full speed is 72MHz whereas the UC3 only gets to 60-66MHz. Given the different architectures though these speeds come out to almost the same MIPS. At maximum speeds though the STM32 is drawing "as low as 27mA" whereas the UC3 with all peripheral clocks running is still at 23.5mA.
joepierson wrote:
The STM32 is cheaper, but doesn't have the large RAM options the AVR32 has.
That is very true.
joepierson wrote:
The STM32 is a ARM based processor, which is nice.
So-so, I reckon if you don't know one arch over the other the avr32 is easier to learn as you only have to go through one (well written!) document from one company to find out all you need to know.

My $0.02 :)

-S.

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squidgit wrote:
The UC3 is optimized for power too, static sleep modes are down at 4uA (admittedly the STM32 can get down to 2uA but when you're this low you godda ask yourself just how much you care ;) )
.

Where are you getting the 4uA number from?

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joepierson wrote:
squidgit wrote:
The UC3 is optimized for power too, static sleep modes are down at 4uA (admittedly the STM32 can get down to 2uA but when you're this low you godda ask yourself just how much you care ;) )
.
Where are you getting the 4uA number from?
'twas from the UC3B datasheet, table 32-2 rev C. but you're right, I did misread the data there, the _total_ sleep current consumption is closer to 20uA. My bad :)

-S.

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Into the Ukraine
the STM32F100C4T6B is cost ~ $1.6,
the AT32UC3A1256 is cost ~ $8.
Powerful argument.

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4RESTER wrote:
Into the Ukraine
the STM32F100C4T6B is cost ~ $1.6,
the AT32UC3A1256 is cost ~ $8.
Powerful argument.

Thats not fare comparing MCU prices:
16KB flash, 4KB SRAM (STM32F100C4T6B) VS
256KB flash, 64KB SRAM (AT32UC3A1256)

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I would worry about the lifetime of the AVR32 architecture. Actually, I'd worry about all 32bit architectures other than ARM and x86. Which is a bit sad, I guess.

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DieCore wrote:
4RESTER wrote:
Into the Ukraine
the STM32F100C4T6B is cost ~ $1.6,
the AT32UC3A1256 is cost ~ $8.
Powerful argument.

Thats not fare comparing MCU prices:
16KB flash, 4KB SRAM (STM32F100C4T6B) VS
256KB flash, 64KB SRAM (AT32UC3A1256)

It is. But when the MCU need for mid-range applications, this (STM32F100C4T6B) will be the best choice.
In this category I would also add LPC2102, a good chip, but the high cost ~ $8