7029 A place to share, learn, and grow... en-US Fri, 22 Jan 2016 00:22:46 +0000 http://bbpress.org/?v=1.0.2 q http://forums.leaflabs.com/search.php http://forums.leaflabs.com/topic.php?id=15451&page=2#post-30976 Fri, 20 Sep 2013 17:49:02 +0000 mlundinse 30976@http://forums.leaflabs.com/ <p>timer.setPrescaleFactor(1);</p> <p>This should do it if timer is the hardware timer connected to the specific pin.</p> <p>The RM does not say PWM must be 550. I have tested it at 1.1 kHz with 16 bit resolution. </p> http://forums.leaflabs.com/topic.php?id=15451#post-30975 Fri, 20 Sep 2013 17:46:18 +0000 mlundinse 30975@http://forums.leaflabs.com/ <p>just set the division factor to one (0 in the PSC registers) and its 1.1 kHz </p> http://forums.leaflabs.com/topic.php?id=15451#post-30974 Fri, 20 Sep 2013 17:28:19 +0000 crk 30974@http://forums.leaflabs.com/ <p>Hi, thank you everyone for the explanations.<br /> So in conclusion the reference page is plenty wrong about the frequency,<br /> all the outputs coming from all timers (TIM1 included) has not the 1.1kHz frequency.<br /> Not only my oscilloscope, but also the RM0008 manual interpretation says the frequency has to be 550Hz! ;)<br /> I'll contact the Leaflabs team for one their opinion. </p> http://forums.leaflabs.com/topic.php?id=15451#post-30954 Thu, 19 Sep 2013 15:17:59 +0000 mlundinse 30954@http://forums.leaflabs.com/ <p>The base timer clocks are running at 72Mhz. For a 36 MHz bus, bus clock divisor 2, the timer clock is 2x the bus clock as seen in the timer tree for the RCC.</p> <p>The setup value of the prescale registers is set 1, giving a prescale division factor of 2, making the timers run at 36 MHz.<br /> With an auto reload of 65536 ( 0xFFFF ) this will give about 550Hz.</p> <p>The setting of PSC = 1 is done in wirish/boards.cpp : timer_default_config() </p> http://forums.leaflabs.com/topic.php?id=15451#post-30888 Thu, 19 Sep 2013 12:25:35 +0000 gbulmer 30888@http://forums.leaflabs.com/ <p>crk - AFAICT you are correct, the code only sets upcounting. IMHO, you are also correct that the reference page is (partly) wrong.</p> <p>The Maple start-up code sets all timers pre-scaler is 0xFFFF, so if the source clock were 72MHz, then 72MHz / 0xFFFF = 1,099Hz</p> <p>However, Timer 1, is AFAICT on a different clock 'domain' (or bus), APB2, to the other timers which are on APB1 ('domain' or bus).</p> <p>APB2 can run at 72MHz but APB1 runs at a maximum of 36MHz ("Figure 11. Clock tree", page 123/1096, RM0008, Doc ID 13902 Rev 14)</p> <p>The RM0008 manual says: "The maximum frequency of the AHB and the APB2 domains is 72 MHz. The maximum allowed frequency of the APB1 domain is 36 MHz." (page 124/1096)</p> <p>So, assuming I've read the manual correctly, the input clock to Timer 1 should be 72MHz, and the input clock to the other Timers should be 36MHz. Timers running at 36MHz should have a period of 36MHz/0xFFFF = 549Hz.<br /> So that, combined with upcounting only, would explain that part of your measurement.</p> <p>IMHO you are correct, the page you linked is incorrect for the 'General Purpose' timers (TIM2 to TIM5).<br /> However AFAICT Timer 1 (TIM1) should be running at 72MHz.</p> <p>So I don't understand why outputs from Timer 1 are running at the same frequency, and not twice that frequency.</p> <p>IIRC I've only measured the frequency of timer pulses when I am trying to get the timer to run at a specific frequency, usually by fiddling with the prescale value. </p> http://forums.leaflabs.com/topic.php?id=15451#post-30825 Thu, 19 Sep 2013 04:07:28 +0000 crk 30825@http://forums.leaflabs.com/ <p>Hi gbulmer, and thank you for your interest!<br /> I have measured this frequency with my oscilloscope in each pwm pin,<br /> and comparing each pin with each other i noticed they are all rising edge alligned.<br /> So i think all counters are up counters and all setted identically.<br /> I'm talking about a Maple running at its bootloader defaults without modifying any timers registers.<br /> Infact i don't have nothing particular to do, but i only wants to know if it is an issue or if the reference page linked before has been written wrong.<br /> Have yuo ever measured the pwm frequency of your maple?<br /> Thank you! </p> http://forums.leaflabs.com/topic.php?id=15451#post-30747 Wed, 18 Sep 2013 21:12:41 +0000 gbulmer 30747@http://forums.leaflabs.com/ <p>crk - Welcome to the forum. I hope we can help.</p> <p>How are you measuring the frequency?</p> <p>It's almost 3am here, so I'm not going to check, on a Maple I'm off to bed.<br /> However, I think it might be slightly misleading documentation.</p> <p>There are a bunch of modes that Maple's STM32F103 (and Arduino ATmega) timers can operate in.</p> <p>One mode counts from 0 to 'max' in one cycle, then counts down from 'max' to 0 in one cycle, then it repeats counting up, then down. So each PWM pulse takes two cycles of the timer.</p> <p>IIRC, this is the mode which two of the Arduino's three timers use (the other is the clock for millis, and operates as a single cycle 0 to 255, 0 to 255 ... counter).</p> <p>I also think it is the mode that the Maple's STM32F103's timers are running in. This is called "Center-aligned mode (up/down counting)" in the RM0008 manual. It says "Center-aligned mode is active when the CMS bits in TIMx_CR1 register are not equal to '00'." (page 359/1096)</p> <p>The register is TIMx_CR1, and the CMS bits are bits are bits 5 &amp; 6 (page 388/1096)</p> <p>If you need it to run at 1.1KHz, you could do several things, using the timer API <a href="http://leaflabs.com/docs/lang/api/hardwaretimer.html#lang-hardwaretimer" rel="nofollow">http://leaflabs.com/docs/lang/api/hardwaretimer.html#lang-hardwaretimer</a></p> <p>If you explain what you need to do, we may be able to help.</p> <p>(Full disclosure: I am not a member of LeafLabs staff.) </p> http://forums.leaflabs.com/topic.php?id=15451#post-30743 Wed, 18 Sep 2013 17:16:50 +0000 crk 30743@http://forums.leaflabs.com/ <p>Hi everyone!<br /> I have a trouble in using PWM in Maple (r5 with ide 0.0.12)<br /> The frequency should be 1.1kHz,<br /> as written here under "Difference 4: PWM frequency":<br /> <a href="http://leaflabs.com/docs/lang/api/analogwrite.html#lang-analogwrite" rel="nofollow">http://leaflabs.com/docs/lang/api/analogwrite.html#lang-analogwrite</a><br /> But in each of pwm pin (i tried pin 0 1 2 3 5 6 7 8 9 11 12 14 24 27 28) i have a frequency of 550Hz!<br /> The delay(), micros() and millis() functions are properly working.<br /> I have a "faulty" Maple or is there a mistake in the reference page?<br /> Is it a known issue?<br /> Anyone had this problem before?<br /> Thank you </p>