One way to generate high speed signal

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One way to generate high speed signal

(8 posts) (3 voices)

Started 4 years ago by gulu2065
Latest reply from gbulmer

gulu2065
Member

Yesterday I found one interesting (For a green hand, I think so,) way to generate high frequency signal.
I post here, hope it will help anyone needed

#define PIN_B6_HIGH (GPIOB_BASE)->BSRR = BIT(6)
#define PIN_B6_LOW (GPIOB_BASE)->BRR = BIT(6)

void setup() {
pinMode(5, OUTPUT); // B6 is pin 5
}

void loop() {
myloop:
PIN_B6_HIGH;
PIN_B6_LOW;
goto myloop;
}

If you want to moderate frequency or duty,
you could use this delay
__asm__("nop\n\t");
it could offer a 30ns? I forget exact number but much shorter than the delayMicrosenonds();

Posted 4 years ago #
mbolivar
LeafLabs

gulu2065,

you may find this FAQ interesting:

http://leaflabs.com/docs/faq.html#how-do-i-write-to-a-pin-at-high-speed

Posted 4 years ago #
gulu2065
Member

mbolivar,
this is great, In fact I just reading something like this.
Now I am interesting in how to write several port at the same time, i.e. let them work at the same speed and thus generate abitrary bits I want.
Do you have any idea about it?

Posted 4 years ago #
mbolivar
LeafLabs

Do you really want to say several ports? You can't write to pins on different ports (like GPIOA and GPIOB) with the same instruction.

If what you mean is several bits, then you can just pick two pins on the same port using your board's pin map, and use the bit set/reset register, BSRR, to set or clear both bits at the same time. See ST RM0008 (linked to here) for more information.

Edit: for example, you could say

GPIOB_BASE->BSRR = BIT(6) | BIT(5);

to set both bit 6 and 5 (on GPIOB) at the same time. To clear them at the same time, you could use

GPIOB_BASE->BSRR = BIT(6 + 16) | BIT(5 + 16);

Posted 4 years ago #
gbulmer
Moderator

You might find these threads useful too:
http://forums.leaflabs.com/topic.php?id=774
http://forums.leaflabs.com/topic.php?id=895 (and the threads it references)

Posted 4 years ago #
mbolivar
LeafLabs

gbulmer,

Thanks for the links. I've added a link to thread with id=895 to the FAQ entry:

https://github.com/leaflabs/leaflabs-docs/commit/dc70ddaad588c23525c3e8ff4ba080e0ac313719

(A link to the thread with id=774 is already present).

Posted 4 years ago #
gulu2065
Member

mbolivar,
are you sure this will work?
I tried but it do not set them both. Only set one.
Could you explain it in more detail?
Thanks,

Posted 4 years ago #
gbulmer
Moderator
gulu2065 - that should work.

Did you check the correct pins?
http://leaflabs.com/docs/hardware/maple.html#master-pin-map
PB5 is pin D4 and
PB6 is pin D5

Did you set the pinMode for those pins?
```
pinMode(D4, OUTPUT);
pinMode(D5, OUTPUT);
```
It might be easier to work backwards, and use the pin map to figure out which pins you want to check.

(full disclosure: I am not a member of LeafLabs staff)
Posted 4 years ago #

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