LeafLabs Garden » Topic: How come similar sentence take different time to execute?

LeafLabs Garden » Topic: How come similar sentence take different time to execute? http://forums.leaflabs.com/topic.php?id=1060 A place to share, learn, and grow... en-US Fri, 22 Jan 2016 00:24:14 +0000 http://bbpress.org/?v=1.0.2 <![CDATA[Search]]> q http://forums.leaflabs.com/search.php mbolivar on "How come similar sentence take different time to execute?" http://forums.leaflabs.com/topic.php?id=1060#post-6521 Thu, 22 Sep 2011 10:20:21 +0000 mbolivar 6521@http://forums.leaflabs.com/ Ah, good point. gbulmer on "How come similar sentence take different time to execute?" http://forums.leaflabs.com/topic.php?id=1060#post-6520 Thu, 22 Sep 2011 10:11:27 +0000 gbulmer 6520@http://forums.leaflabs.com/ mbolivar - AFAIK, the program needs to generate a 1.6MHz clock signal, and read data coming in from a pin at that rate. I think this may be exactly an SPI-style problem, but I also think an STM32F has just about enough raw horse-power to do it in software. It might migrate to SPI, or even SPI+DMA. (full disclosure: I am not a member of LeafLabs staff) mbolivar on "How come similar sentence take different time to execute?" http://forums.leaflabs.com/topic.php?id=1060#post-6514 Thu, 22 Sep 2011 09:35:02 +0000 mbolivar 6514@http://forums.leaflabs.com/ <blockquote> - a table with the values for the port pin values: </blockquote> I have used this approach on Maple. With systick and USB disabled, it results in extremely regular timing. However, if all you're doing is toggling a pin at a predefined rate, then PWM is fastest. See the forum posts referenced in the FAQ: <a href="http://leaflabs.com/docs/faq.html#how-do-i-write-to-a-pin-at-high-speed" rel="nofollow">http://leaflabs.com/docs/faq.html#how-do-i-write-to-a-pin-at-high-speed</a> gbulmer on "How come similar sentence take different time to execute?" http://forums.leaflabs.com/topic.php?id=1060#post-6506 Wed, 21 Sep 2011 16:45:57 +0000 gbulmer 6506@http://forums.leaflabs.com/ gulu2065 <blockquote>Did you want me to compare the two signal (bit(5)and bit (6))? </blockquote> Yes, on a dual trace oscilloscope. <blockquote>Their produce are the same. </blockquote> That sequence should toggle bit 6 of port B 5 times, and bit 5 once each time around the while loop. If it doesn't, there is something going wrong. To avoid confusion: <pre><code>while (1) { GPIOB_BASE->BSRR = BIT(6) | BIT(5); GPIOB_BASE->BSRR = BIT(6+16); GPIOB_BASE->BSRR = BIT(6); GPIOB_BASE->BSRR = BIT(6+16); GPIOB_BASE->BSRR = BIT(6); GPIOB_BASE->BSRR = BIT(6+16); GPIOB_BASE->BSRR = BIT(6); GPIOB_BASE->BSRR = BIT(6+16); GPIOB_BASE->BSRR = BIT(6); GPIOB_BASE->BSRR = BIT(6+16) | BIT(5+16); }</code></pre> <blockquote>Do you have any other ideas to generate a 1.6 Mhz clock and at the same time generate several bits (less than 20) which is synchronously with the 1.6Mhz? </blockquote> You could use: - a similar code sequence, but with all the signal encoded so there is no loop, or - SPI (running as a slave, with a timer to generate the correct baud rate), or - a timer and DMA to write bit patterns to the port pins, or - a table with the values for the port pin values: <pre><code>uint32 pinValues[] = { BIT(6) | BIT(5); BIT(6+16); BIT(6) | BIT(5); BIT(6+16); BIT(6) | BIT(5); BIT(6+16); BIT(6) | BIT(5); BIT(6+16); BIT(6) | BIT(5); BIT(6+16) | BIT(5+16); ... }; ... for (int i=0; i<sizeof(pinValues[])/sizeof(uint32); ++i) { GPIOB_BASE->BSRR = pinValues[i]; }</code></pre> Edit: I made a mistake, the types should be uint32, and not uint16. I have corrected that in the code above. (full disclosure: I am not a member of LeafLabs staff) gulu2065 on "How come similar sentence take different time to execute?" http://forums.leaflabs.com/topic.php?id=1060#post-6505 Wed, 21 Sep 2011 16:06:08 +0000 gulu2065 6505@http://forums.leaflabs.com/ gbulmer, I am a little confused by this Then you might see the delay due to the loop on the display on bit 5 trace. Did you want me to compare the two signal (bit(5)and bit (6))? Their produce are the same. Do you have any other ideas to generate a 1.6 Mhz clock and at the same time generate several bits (less than 20) which is synchronously with the 1.6Mhz? Thanks gbulmer on "How come similar sentence take different time to execute?" http://forums.leaflabs.com/topic.php?id=1060#post-6503 Wed, 21 Sep 2011 15:31:58 +0000 gbulmer 6503@http://forums.leaflabs.com/ gulu2065 - I have done similar code. There are only two explanations I can think of: 1. other interrupts are casing the signal to jitter. If you are observing this on a normal oscilloscope, the interrupts will be quite rare (about 1 ms) compared to the signal, so that might not be the cause. 2. The actual instruction sequence might not have enough registers to hold all of the constant values, so the sequence has an extra load register or two between them. Test that hypothesis with the simpler sequence: <pre><code>while (1) { GPIOB_BASE->BSRR = BIT(6) | BIT(5); GPIOB_BASE->BSRR = BIT(6+16); GPIOB_BASE->BSRR = BIT(6) | BIT(5); GPIOB_BASE->BSRR = BIT(6+16); GPIOB_BASE->BSRR = BIT(6) | BIT(5); GPIOB_BASE->BSRR = BIT(6+16); GPIOB_BASE->BSRR = BIT(6) | BIT(5); GPIOB_BASE->BSRR = BIT(6+16); GPIOB_BASE->BSRR = BIT(6) | BIT(5); GPIOB_BASE->BSRR = BIT(6+16) | BIT(5+16); }</code></pre> Are you checking on a dual trace oscilloscope? If you are, you might be able to get the 5 cycles (bit 6) of that sequence on one trace, and the other signal (bit 5) on the other. Then you might see the delay due to the loop on the display on bit 5 trace. gulu2065 on "How come similar sentence take different time to execute?" http://forums.leaflabs.com/topic.php?id=1060#post-6501 Wed, 21 Sep 2011 15:22:59 +0000 gulu2065 6501@http://forums.leaflabs.com/ gbulmer, what I mean is the difference between each GPIOB_BASE->BSRR = ... Not related to loop or while(). I mean, GPIOB_BASE->BSRR = BIT(6) | BIT(5); set both high and GPIOB_BASE->BSRR = BIT(6+16) | BIT(5+16); set both low ... ... when repeat this, I hope I can see a regular signal with the same delay between the several bits. While the delay seems irregular and do not make sense. Thanks gbulmer on "How come similar sentence take different time to execute?" http://forums.leaflabs.com/topic.php?id=1060#post-6500 Wed, 21 Sep 2011 14:55:05 +0000 gbulmer 6500@http://forums.leaflabs.com/ The overhead for calling loop() is quite significant compared to the time between two <code>GPIOB_BASE->BSRR = ...</code> There is really a function called main() which is roughly: <pre><code>int main(...) { ... setup(); while (1) loop(); }</code></pre> That <code>while</code> and call of loop() will be much slower than the goto, or: <pre><code>while (1) { GPIOB_BASE->BSRR = BIT(6) | BIT(5); GPIOB_BASE->BSRR = BIT(6+16) | BIT(5+16); GPIOB_BASE->BSRR = BIT(6) | BIT(5); GPIOB_BASE->BSRR = BIT(6+16) | BIT(5+16); GPIOB_BASE->BSRR = BIT(6) | BIT(5); GPIOB_BASE->BSRR = BIT(6+16) | BIT(5+16); GPIOB_BASE->BSRR = BIT(6) | BIT(5); GPIOB_BASE->BSRR = BIT(6+16) | BIT(5+16); GPIOB_BASE->BSRR = BIT(6) | BIT(5); GPIOB_BASE->BSRR = BIT(6+16) | BIT(5+16); }</code></pre> You might adjust the timing between each <code>GPIOB_BASE->BSRR = ...</code> with <code>__asm__("nop\n\t");</code> as mentioned in one of the other threads. That would allow you to get close to having the jump instructions for the goto or while match the gaps between the <code>GPIOB_BASE->BSRR = ...</code> SPI is worth looking at. Look at disabling the interrupts too: See <a href="http://leaflabs.com/docs/lang/api/serialusb.html#lang-serialusb" rel="nofollow">http://leaflabs.com/docs/lang/api/serialusb.html#lang-serialusb</a> I think it is USBSerial::end() <a href="http://leaflabs.com/docs/libmaple/api/systick.html?highlight=systick" rel="nofollow">http://leaflabs.com/docs/libmaple/api/systick.html?highlight=systick</a> void systick_disable() gulu2065 on "How come similar sentence take different time to execute?" http://forums.leaflabs.com/topic.php?id=1060#post-6499 Wed, 21 Sep 2011 14:49:18 +0000 gulu2065 6499@http://forums.leaflabs.com/ I find even this basic repeat do not produce a regular signal!(The same time delay between each bits) Why is that?? void setup () { pinMode(D4, OUTPUT); pinMode(D5, OUTPUT); } void loop(){ GPIOB_BASE->BSRR = BIT(6) | BIT(5); GPIOB_BASE->BSRR = BIT(6+16) | BIT(5+16); GPIOB_BASE->BSRR = BIT(6) | BIT(5); GPIOB_BASE->BSRR = BIT(6+16) | BIT(5+16); GPIOB_BASE->BSRR = BIT(6) | BIT(5); GPIOB_BASE->BSRR = BIT(6+16) | BIT(5+16); GPIOB_BASE->BSRR = BIT(6) | BIT(5); GPIOB_BASE->BSRR = BIT(6+16) | BIT(5+16); GPIOB_BASE->BSRR = BIT(6) | BIT(5); GPIOB_BASE->BSRR = BIT(6+16) | BIT(5+16); } gbulmer on "How come similar sentence take different time to execute?" http://forums.leaflabs.com/topic.php?id=1060#post-6497 Wed, 21 Sep 2011 14:36:40 +0000 gbulmer 6497@http://forums.leaflabs.com/ There are two interrupts, systick and USB running which may make the value jitter. You can disable them. The delay between <pre><code>GPIOB_BASE->BSRR = BIT(6+16) | BIT(5); GPIOB_BASE->BSRR = BIT(6) | BIT(5);</code></pre> will be different to <pre><code>GPIOB_BASE->BSRR = BIT(6+16) | BIT(5); goto myloop; ... myloop: GPIOB_BASE->BSRR = BIT(6) | BIT(5);</code></pre> I can't think of much you can do about that. SPI would be more accurate if you can get the clock speed correct. (full disclosure: I am not a member of LeafLabs staff) gulu2065 on "How come similar sentence take different time to execute?" http://forums.leaflabs.com/topic.php?id=1060#post-6493 Wed, 21 Sep 2011 13:35:47 +0000 gulu2065 6493@http://forums.leaflabs.com/ I want to use the following sentence to generate several bits to configure my chip. As planned, Pin 4 should output a 11001 bits synchronously with Pin 5, which is a CLK. However, when I measure it on the scope, I find it take different time for each command and I get the five bits with different intervals. Any suggestions? void setup () { pinMode(D4, OUTPUT); pinMode(D5, OUTPUT); } void loop(){ myloop: GPIOB_BASE->BSRR = BIT(6) | BIT(5); GPIOB_BASE->BSRR = BIT(6+16) | BIT(5); GPIOB_BASE->BSRR = BIT(6) | BIT(5); GPIOB_BASE->BSRR = BIT(6+16) | BIT(5); GPIOB_BASE->BSRR = BIT(6) | BIT(5+16); GPIOB_BASE->BSRR = BIT(6+16) | BIT(5+16); GPIOB_BASE->BSRR = BIT(6) | BIT(5+16); GPIOB_BASE->BSRR = BIT(6+16) | BIT(5+16); GPIOB_BASE->BSRR = BIT(6) | BIT(5); GPIOB_BASE->BSRR = BIT(6+16) | BIT(5); goto myloop; } Thanks a lot!