Arduino for STM32

Seems to be an interesting chip, and I can see there is some arduino ide support.

Gullik

Well, I was just testing to see how it works.

One idea was to make a simple logic analyzer, aka Salae, but with twice the bits, and 60 Mhz sample rate. If one locks out interrupts, or never enable
them while collecting samples it *could* be done with programmed I/O.

However, doing it with DMA ...

And, END of investigation:

A straight sequence of assmbly iread/write statements produces a jitterfree square wave on the io pins.

asm volatile (
"gpiobport = 0x40010c0c \n\t"
"ldr r1, =datarray \n\t"
"ldr r2, =gpiobport \n\t"
"ldrh r0, [r2],#0 \n\t"
"str.w r0, [r1],#2 \n\t"
"ldrh r0, [r2 ...

"I don't see why you need "& 0xffff" on those statements, but fortunately the compiler seems to be smart enough to achieve that just by the choice of instructions to use."

Well, i got a problem trying to write a 16-bit (uint16_t) into a 32 bit register (uint32_t). The & 0xffff is interpreted as ...

Now with redeclared GPIOB definition

volatile unsigned int *GPIOBPORT = (volatile unsigned int *)0x40010C0C;

I have the unrolled loop:

datptr = &datarray[0];
snapshot = *DWT_CYCCNT;
*GPIOBPORT = *datptr++ & 0xffff;
*GPIOBPORT = *datptr++ & 0xffff;
*GPIOBPORT = *datptr++ & 0xffff;

total of ...

Tnx ozcar,

Yes, I have thougt about optimizations, unfortunately this is not a choice with the AT32F403A, at least not from the menu.

Also, the attribute volatile will / might change the compiler code generator. I will check this out.

Right now I am getting confusing results.
The loop
for(k=0;k ...

Granted::

it doesn't seem to be what your code is doing.

Correct: No the printing of a fixed string screws that up of course, this would have been better.

scratch = *DWT_CYCCNT - snapshot;
Serial.print("Whatever");
Serial.println(scratch);

would be better. However, I am alternating with ...

"did a quick scan and not sure if i got what you were trying to do. but to get accurate timing, don't blend your serial output in there."

I figured the Serial.printf is executed AFTER the calculation of (*DWT_CYCCNT - snapshot) which means it does not matter,

To explain what I am trying to do, is ...

Hello dannyf (and others)

I have actually done what you suggested, but am now stuck with something different......

Now I have struck another problem, which I guess is either the c compiler or objdump

It seems to me that the compiler will not generate code for all these output statements
OR that ...

My foggy understanding is clearing up......

"The result is a square wave on the pins, 30nS high and 30nS low, which equates to 16.67 Mhz, i.e. each sample 33 Mhz. It seems the cpu takes
5 instructions to write a word to GPIO. CPU clock is 240 Mhz as I have configured it. I would have hoped for a ...