$1 MCU review — looking for AVR part suggestions

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Paulvdh wrote:

Some time ago I dipped a part of my littlest pinky toe in the ARM world. (STM32F103C8T6)

It's a 32 bit processor but the I/O structure (timers, etc) is apparently mostly 16 bit.

That's one of my pet peeves with some ARMs. I cannot see the sense in a 32b MCU, with 16b Timers ?

Some 8b MCUs even allow Timer cascade to 32b, such is the demand for the better dynamic range/precision.

 

NXP 'gets this' & have (IIRC) 32b timers and 32b prescalers, and Nuvoton are close, with 24b timers.

 

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Paulvdh wrote:

Ah, so that is the "steering" part.

Triggers a memory about a story floating on (or sunk deep into) the 'net.

It was about a uC occasionallly losing bits in it's I/O configuration registers. The whole uC (or FPGA?) kept running happily, just some outputs stopped outputting the right signals untill the uC got a hardware reset. Then it worked all perfectly for a while, so no hardware pins blown, but the problem kept recurring.

The likely culprit was probably marginal decoupling / emc design, whatever but investigating and PCB revisions take time.

 

So as a (temporary) solution they put the whole I/O configuration in flash and used a periodic interrupt to rewrite it to the I/O ports.

That's more common than you realize, and is somewhat standard ESD hardening. Always a good idea to 'refresh the config', where practical.

 

Worse was the part where we found Reset was more of a 'Reset Request', and it could disable under ESD stress tests - outcome was a Power Removal watchdog design, that I'm surprised is not seen much.

 

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