[beagleboard] Using DMtimer pins to measure pulse width
I'm trying to use the timer pins (gpio2[2...5]) to measure pulse with on a BBB with the 25 MHz clock. The pin mud mode is correctly set to 2 and pull up/down are disabled and capture mode is set on the timers. When I connect a push button attached to 3.3v to one of the four timer pins I correctly get capture interreupts on low to high and high to low transitions and I can measure the timer difference between them without issue. However, if I set up a signal generator for 50 Hz 3.3v square wave and attach it to a timer pin, I get no interrupts at all. Looking on a 'scope at the timer pin, the pulse train amplitude has drop from 3.3 volts to about 1.3v. Does anyone have any ideas on what would cause such a drop in amplitude? Thanks for any suggestions. Bob Stewart -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups BeagleBoard group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[beagleboard] Using DMTimer pins to measure pulse width.
I'm trying to use the DMTimer pins (gpio2[2...5]) to measure pulse width using the 25MHz clock. I've successfully tested the software using a button connected to the 3.3v rail. The pinmux is set to mode 2 forcthose pins and pull up/down are disabled. The timers are set up in capture mode with interrupts enabled on the edge transitions. Using the button the interrupts occur and the time between the edges is derived from the captured timer values. However, when I connect a signal generator outputting a 3.3v amplitude square wave at 50Hz to a timer pin, no interrupts occur. Looking on a 'scope at the input to the timer pin the pulse train amplitude has dropped to about 1 volt. Can anyone suggest possible cause for this drop in amplitude? Thanks for any suggestions. Bob Stewart -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups BeagleBoard group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [beagleboard] PWM Subsystem Time Base input clock frequency?
On Friday, January 31, 2014 5:57:32 PM UTC-5, Charles Steinkuehler wrote: On 1/31/2014 12:38 PM, robjsstew...@gmail.com wrote: According to the TRM, the Time Base module on each of the PWM subsystems is clocked directly from the cpu clock. That is, its being clocked at a period of 1 nsec. Where exactly are you seeing this? Virtually nothing on the chip but the ARM cores and directly connected caches will be running at 1 GHz. I show the PWMSS to be clocked by the L4 interconnect clock (see section 15.1.2.2) with a maximum functional clock frequency of 100 MHz (15.1.2.3). The L4_PER domain the PWM units are all connected to is for slow peripherals. The L4_Fast domain used for the PRU is only 200 MHz, and I'd be surprised if you could configure the L4_PER clock to be over 100 MHz (but I haven't crawled through all the clock routing and power management logic to prove this). It can be prescaled down to 1/128,for a period of 128 nsecs. The period and the counter compare registers are only 16 bits wide so the minimum PWM frequency is about 120 MHz. Is that correct? Take all your GHz numbers and divide by 10 for the actual 100 Mhz clock frequency. -- Charles Steinkuehler char...@steinkuehler.net Thanks for the reply, Charles. That makes sense. Table 15-12 on page 2006 of the TRM refers to TBCLK being a prescaled version of SYSCLKOUT which is, later in that section, mentioned to be the cpu clock, or so I remembered. Thanks very much. Bob Stewart -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups BeagleBoard group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
[beagleboard] PWM Subsystem Time Base input clock frequency?
According to the TRM, the Time Base module on each of the PWM subsystems is clocked directly from the cpu clock. That is, its being clocked at a period of 1 nsec. It can be prescaled down to 1/128,for a period of 128 nsecs. The period and the counter compare registers are only 16 bits wide so the minimum PWM frequency is about 120 MHz. Is that correct? Bob Stewart -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups BeagleBoard group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
[beagleboard] Re: PWM Subsystem Time Base input clock frequency?
On Friday, January 31, 2014 1:38:32 PM UTC-5, robjss...@gmail.com wrote: According to the TRM, the Time Base module on each of the PWM subsystems is clocked directly from the cpu clock. That is, its being clocked at a period of 1 nsec. It can be prescaled down to 1/128,for a period of 128 nsecs. The period and the counter compare registers are only 16 bits wide so the minimum PWM frequency is about 120 MHz. Is that correct? Bob Stewart sigh...thanks, you are correct. But, it is fast than I would have expected. -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups BeagleBoard group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
[beagleboard] Re: PWM Subsystem Time Base input clock frequency?
On Friday, January 31, 2014 1:48:09 PM UTC-5, Peter Baltus wrote: I guess I would argue that with 16 bits the counter can count up to 65535 and wrap around after 65536 counts of 128ns max. That gives a max period of the PWM of 8.39ms and a min frequency of 119Hz - I think. But it has been a long day, so I might very well be very wrong ;-) Peter Sigh...you are correct! But it's still a higher frequency than I expected for the slowest PWM signal. I thought that the input clock might not be at the cpu frequency. Thanks. -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups BeagleBoard group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
Re: [beagleboard] Cortex-A8 version supported on the AM3358?
Thanks. Bob -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups BeagleBoard group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
[beagleboard] Cortex-A8 version supported on the AM3358?
I'm running the Genode OS on a BBB and am having issues with the MMU. What version of the Cortex-A8 processor is the BBB based on? The current version is r3p2. Thanks, Bob Stewart -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups BeagleBoard group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
