BeagleBoardPWM - Revision history

Yoder: Moved to ECE597

2013-05-18T15:42:44Z

Moved to ECE597

Yoder: /* OMAP3530 PWM library */ Links to code are broken, so I added to pointer to my git repository.

2012-04-12T12:42:56Z

‎OMAP3530 PWM library: Links to code are broken, so I added to pointer to my git repository.

Yoder: Removed analytics

2011-09-22T15:30:41Z

Removed analytics

Yoder at 15:38, 17 August 2011

2011-08-17T15:38:06Z

Yoder: /* OMAP Mux Configuration */ Added note about using u-boot to set the pin mux

2011-07-25T17:22:35Z

‎OMAP Mux Configuration: Added note about using u-boot to set the pin mux

Yoder: /* OMAP Mux Configuration */ Added note about CONFIG_OMAP_MUX

2011-07-22T15:36:35Z

‎OMAP Mux Configuration: Added note about CONFIG_OMAP_MUX

Yoder: /* OMAP3530 PWM library */ Added dmesg in case you aren't running from the console prompt

2011-07-22T14:11:06Z

‎OMAP3530 PWM library: Added dmesg in case you aren't running from the console prompt

Yoder: /* Activating PWM via Timer Registers */ Added DM3730 page numbers

2011-07-22T13:43:24Z

‎Activating PWM via Timer Registers: Added DM3730 page numbers

Nndhawan: /* OMAP3530 PWM library */

2011-03-16T18:02:27Z

‎OMAP3530 PWM library

Nndhawan: /* OMAP3530 PWM library */

2011-03-16T06:15:06Z

‎OMAP3530 PWM library

@@ Line 1: / Line 1: @@
 [[Category:BeagleBoard]]
-[[Category:ECE497]]
+[[Category:ECE597]]
 [[Category:Robotics]]

@@ Line 85: / Line 85: @@
 * [http://www.rose-hulman.edu/~mosttw/omap3530-pwm-1.1.tar.gz omap3530-pwm-1.1.tar.gz] (LGPL/MIT, md5 b33232531321778eadc022fef9cf7bac)
 * [http://www.rose-hulman.edu/~mosttw/omap3530-pwm-1.0.tar.gz omap3530-pwm-1.0.tar.gz] (LGPL only, md5 ff77617cf07450be1444019809c75a0c)
 Information regarding compilation of this program is not included in any README file so to ease compilation problems use the following.  Keep in mind this has been only tested when compiled on the beagleboard and not cross-compiled though it should still shed light if you have problems.

@@ Line 2: / Line 2: @@
 [[Category:ECE497]]
 [[Category:Robotics]]
 There are three pins capable of [http://en.wikipedia.org/wiki/Pulse-width_modulation PWM (pulse-width modulation)] exposed on the C3/C4 BeagleBoard expansion header.  PWM is useful for control of a number of devices, from LEDs (which can be faded smoothly with PWM) to [[ECE597 Project Sumo Robot | DC motors]].  For robotics, this means that three hobby servos can easily be controlled by the Beagle given nothing more than a simple [[BeagleBoard_Hardware_Interfacing#Level_Shifting | level-shifting]] circuit, with no CPU usage to speak of.

@@ Line 2: / Line 2: @@
 [[Category:ECE497]]
 [[Category:Robotics]]
 There are three pins capable of [http://en.wikipedia.org/wiki/Pulse-width_modulation PWM (pulse-width modulation)] exposed on the C3/C4 BeagleBoard expansion header.  PWM is useful for control of a number of devices, from LEDs (which can be faded smoothly with PWM) to [[ECE597 Project Sumo Robot | DC motors]].  For robotics, this means that three hobby servos can easily be controlled by the Beagle given nothing more than a simple [[BeagleBoard_Hardware_Interfacing#Level_Shifting | level-shifting]] circuit, with no CPU usage to speak of.

← Older revision		Revision as of 17:22, 25 July 2011
Line 18:		Line 18:

	Note: Setting the kernel config option CONFIG_OMAP_RESET_CLOCKS to yes [[http://github.com/scottellis/omap3-pwm/blob/master/README \| may cause problems]].		Note: Setting the kernel config option CONFIG_OMAP_RESET_CLOCKS to yes [[http://github.com/scottellis/omap3-pwm/blob/master/README \| may cause problems]].
		+
		+	=== The 2.6.32 kernel ===
		+
		+	I found the above didn't work with the 2.6.32 kernel, rather the MUXing had to be done in u-boot. [[BeagleBoardPinMux#Setting_Mux_Through_u-boot \| Here]] is a nice description of how it is done.

	== Activating PWM via Timer Registers ==		== Activating PWM via Timer Registers ==

@@ Line 15: / Line 15: @@
   OMAP3_MUX(UART2_RTS, OMAP_MUX_MODE2|OMAP_PIN_OUTPUT), /* GTP10_PWMEVT, ball AB25, ex pin 10 */
-Obviously these lines should precede the line terminating the array.
+Obviously these lines should precede the line terminating the array. This will likely be in a block conditional on CONFIG_OMAP_MUX, so you need to have the CONFIG_OMAP_MUX option set in your kernel config.
 Note: Setting the kernel config option CONFIG_OMAP_RESET_CLOCKS to yes [[http://github.com/scottellis/omap3-pwm/blob/master/README | may cause problems]].

@@ Line 92: / Line 92: @@
 <pre>
-root@beagleboard:~#
+root@beagleboard:~# ./pwm-demo
 ./pwm-demo
+Bus error
-[  174.893035] Unhandled fault: external abort on non-linefetch (0x1818) at
+root@beagleboard:~# dmesg | tail -1
-x4001e024
+[  174.893035] Unhandled fault: external abort on non-linefetch (0x1818) at 0x4001e024
-Bus error
 </pre>

@@ Line 21: / Line 21: @@
 == Activating PWM via Timer Registers ==
-PWM output on the BeagleBoard is done via the OMAP processor's general-purpose timer mechanism, described in the OMAP35x TRM in section 16.2.4 (page 2546).  To briefly summarize this (and simplify significantly), the general-purpose timer is a continuously-incrementing counter that can be configured to toggle the PWM output high when a certain value is reached, and low when it overflows.  By adjusting the first number the duty cycle can be set.  Setting the value the counter starts at can be used to set the frequency of the PWM.
+PWM output on the BeagleBoard is done via the OMAP processor's general-purpose timer mechanism, described in the OMAP35x TRM in section 16.2.4 (page 2546, or page 2698 of the DM3730 TRM).  To briefly summarize this (and simplify significantly), the general-purpose timer is a continuously-incrementing counter that can be configured to toggle the PWM output high when a certain value is reached, and low when it overflows.  By adjusting the first number the duty cycle can be set.  Setting the value the counter starts at can be used to set the frequency of the PWM.
 [[File:OMAP3-GPTimer-PWM.svg|thumb|right|300 px|alt="The registers TCRR, TLDR, and TMAR are illustrated as boxes partially-filled from the right.  Lines at the value of TLDR, the value of TMAR, and the end are labeled 'Start', 'Match', and 'Overflow' respectively."]]
@@ Line 27: / Line 27: @@
 [[File:OMAP3-GPTimer-PWM-Waveform.svg|frameless|500 px|alt="A square waveform starting at 0, with the beginning labeled as 'Start'.  Where the waveform goes to 1 it is labeled 'Match', and when it returns to zero it is labeled 'Overflow, Start'.  It then repeats."]]
-Each GP timer has a 4K block for memory-mapped registers (see TRM Table 16-12).  The start addresses of these blocks for the timers on the BeagleBoard are listed below.
+Each GP timer has a 4K block for memory-mapped registers (see TRM Table 16-12, page 2558 OMAP3530 or page 2710 DM3730).  The start addresses of these blocks for the timers on the BeagleBoard are listed below.
 {|border=1
@@ Line 49: / Line 49: @@
 | '''Description'''
 |-
-| TCLR || 16.3.2.6 (p.&nbsp;2568) || 0x024
+| TCLR || 16.3.2.6 (p.&nbsp;2568/2719) || 0x024
 | Control register<!-- (see below) -->.
 |-
-| TCRR || 16.3.2.7 (p.&nbsp;2570) || 0x028
+| TCRR || 16.3.2.7 (p.&nbsp;2570/2721) || 0x028
 | The counter.  Increments with the clock when the timer is running.
 |-
-| TLDR || 16.3.2.8 (p.&nbsp;2571) || 0x02c
+| TLDR || 16.3.2.8 (p.&nbsp;2571/2722) || 0x02c
 | Timer load register.  Holds the value assumed by TCRR when it overflows.
 |-
-| TMAR || 16.3.2.11 (p.&nbsp;2575) || 0x038
+| TMAR || 16.3.2.11 (p.&nbsp;2575/2725) || 0x038
 | Value to be compared with the counter.
 |}

← Older revision		Revision as of 18:02, 16 March 2011
Line 102:		Line 102:
	This is caused because the library does not enable the PWM clocks and you are not allowed to access them until this is done. In order to fix this you need to recompile your kernel with the option CONFIG_OMAP_RESET_CLOCKS disabled. More information can be found in this thread:		This is caused because the library does not enable the PWM clocks and you are not allowed to access them until this is done. In order to fix this you need to recompile your kernel with the option CONFIG_OMAP_RESET_CLOCKS disabled. More information can be found in this thread:
	http://groups.google.com/group/beagleboard/browse_thread/thread/ee42e5c59edf83cd/67be50968de6a9f2?lnk=gst&q=guint8#67be50968de6a9f2		http://groups.google.com/group/beagleboard/browse_thread/thread/ee42e5c59edf83cd/67be50968de6a9f2?lnk=gst&q=guint8#67be50968de6a9f2
		+
		+	or see the note above at: http://elinux.org/BeagleBoardPWM#OMAP_Mux_Configuration

@@ Line 85: / Line 85: @@
 <pre>
-root@beagleboard:~# gcc *.c -o pwm-demo -lglib-2.0 -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include
+root@beagleboard:~# gcc *.c -o pwm-demo -lglib-2.0 -I/usr/include/glib-2.0
 </pre>