WARNING: If your input frequency isn't 24MHz, then default SYSBIOS clock is probably wrong.

Hi Dean,

In the Timer64 module, the default frequency for C6748 Timers is 24MHz. You can change this to 19.2MHz by setting the External Input Clock Frequency in XGCONF as shown below:

Alternatively, if you are creating the timer instance dynamically, you can set the "extFreq.lo" and "extFreq.hi" field in the Timer params to the desired frequency.

Best,

Ashish

I was told in this post, http://e2e.ti.com/support/embedded/bios/f/355/t/238055.aspx that if I'm using the "Internally configured hal Timer to periodically call Clock_tick()" that I should not include the TIMER module.  All the TIMER configuration for the automatically generated hal TIMER is done via SYSBIOS, XGCONF, XDCTOOL, whatever you want to call it (basically the GUI way to config SYSBIOS, not dynamic).

Your suggestion seem wrong, as you leave the TIMER ISR function as null, the period to 0, etc.  Would someone else care to weigh in on this issue?

- Dean

Hi Dean,

My bad, I misread your post. You are right, the Clock() module uses an internally configured timer by default. This internally configured timer runs at the default timer frequency of 24 MHz like I mentioned before. In order to change this frequency you would need to create your own timer that runs at the right frequency and then call Clock_tick() from your timer handler.

The first step is to configure the clock module to stop creating an internally configured timer. Here's how it can be done:

Next, you would create your own Timer with 19.2 MHz External Frequency, set the period (1000 if you want a period of 1ms), and provide your own Timer Handler function. Within the Timer Handler function you need to add a call to Clock_tick(). Make sure to create a periodic and continuous timer.

With he above changes, you would now be providing the tick source for the Clock module and since you create the Timer, you can control its external input frequency.

You can find this info in the Clock module's cdoc too:

http://software-dl.ti.com/dsps/dsps_public_sw/sdo_sb/targetcontent/bios/sysbios/6_35_00_20/exports/bios_6_35_00_20/docs/cdoc/index.html#ti/sysbios/knl/Clock.html

Best,

Ashish

We are shocked.  I don't even want to know how many embedded systems are running SYSBIOS that have the wrong clock rate.  No where in the CLOCK cdoc page does it mention 24MHz is the assumed input clock frequency, and that it can't be changed.  No where in the SYSBIOS users guide is this mentioned.  No where in the SYSBIOS online videos is this mentioned.  No where is this mentioned!!!!!

In DSPBIOS you could setup a TIMER to drive the CLOCK module.  You could define, which timer was used, which HWI vectors was used, load the TIMER values up yourself or have DSPBIOS do it for you based on the information provided in the .cfg file.  In SYSBIOS, you can choose which TIMER to use, but you can't choose which HWI vector gets plugged.  That is some random thing SYSBIOS chooses based on what TIMER was selected.  You can't change the HWI bitmask like you could in DSPBIOS, and now we find out if your board isn't running at 24MHz, you can't use "Use Timer to automatically call Clock_tick()".  Don't you think that would have been helpful information to provide.  I don't know, maybe in the users guide, or how about a warning next to the selection?

For anyone reading this thread, WARNING WARNING WARNING.  If you use CLOCK functions, and you have SYSBIOS automatically configure the timer for you (which is the default), and you aren't running at 24MHz, all of your timer based things will be wrong.  Clock_getTicks(), wrong.  Semaphore_pend with a timeout, wrong.  Basically anything time based that SYSBIOS needs will be wrong.

The frustrating thing is SYSBIOS could figure out the input clock frequency given the CPU frequency.  Using the registers in PLL0 you can work backwards to figure out the input clock.  Since we no longer saw the input clock setting when moving from DSPBIOS to SYSBIOS, I assumed that is what you were doing.

- Dean

Hi Dean,

I found another simpler way to change the Clock frequency without having to change the Clock tick source.You can use the intFreqs global configuration parameter to do so. Here's some example code that you would need to add to your *.cfg file:

var Timer = xdc.useModule('ti.sysbios.timers.timer64.Timer');
Timer.intFreqs[Timer_Id].lo = 1920000;     
Timer.intFreqs[Timer_Id].hi = 0;

// Timer_Id in your case would depend on the Timer Id used by the Clock Module. You can look at Clock Module's ROV view to determine the Timer Id used by it. Or, if you are specifying the Timer Id the Clock Module should use in XGCONF then you already know what Id to use.

Please note that if you use intFreqs[] to change the default Timer frequency, you can let the clock module internally configure the timer.

I have filed a bug to add a Timer Frequency table to the cdoc that shows the default timer frequencies used by SYS/BIOS:

https://cqweb.ext.ti.com/cqweb/main?command=GenerateMainFrame&service=CQ&schema=SDO-Web&contextid=SDOWP&entityID=SDOCM00100884&entityDefName=IncidentReport&username=readonly&password=readonly

I would also like to point out that it is possible to view the timer frequency used by a particular timer if you look at the Timer module's ROV view:

I also filed a bug to update the timer64 cdoc with an example showing how the default Timer Frequency can be modified using the intFreqs global config param:

https://cqweb.ext.ti.com/cqweb/main?command=GenerateMainFrame&service=CQ&schema=SDO-Web&contextid=SDOWP&entityID=SDOCM00100886&entityDefName=IncidentReport&username=readonly&password=readonly

Hope this helps!

Best,

Ashish

Ashish, thanks for providing a quick solution.  Your suggestion of modifying the .cfg file worked.  Now when I open our .cfg file using XGCONF, I see it added a new Timer module.  It has added:  SYSBIOS -> Target Specific Support -> C64P -> Timers -> Timer64 Timer.  Our DSP is the C6748.  Should we be using the C674 Target specific timer instead?  If so, how do you modify your first line to select the C674 Timer?

For all SYSBIOS developers, this was a major oversight.  The default SYSBIOS configuration configures TIMER0 to provide the system clock ticks.  Not only have you removed the ability to change which HWI ISR vector TIMER0 uses, and what bitmask it can use, you have assumed that EVERYONE is running their project with a  24MHz input frequency.  No warnings, no mention of the 24MHz restriction, no work around (well not until one was provided by Ashish), etc.

I strongly suggest XGCONF gets modified so EVERYTHING related to this TIMER can be accessed (HWI vector, HWI bitmask, making sure the PRD is configured correctly based on the input frequency, etc).  Leaving things hard coded and un-documented is a huge no-no.

- Dean

Hi Dean,

Dean Hofstetter said:

Ashish, thanks for providing a quick solution.  Your suggestion of modifying the .cfg file worked.  Now when I open our .cfg file using XGCONF, I see it added a new Timer module.  It has added:  SYSBIOS -> Target Specific Support -> C64P -> Timers -> Timer64 Timer.  Our DSP is the C6748.  Should we be using the C674 Target specific timer instead?  If so, how do you modify your first line to select the C674 Timer?

The Timer64 module also supports the C6748 device.

You can look at the Timer Mapping Table for a list of devices supported by Timer64: http://software-dl.ti.com/dsps/dsps_public_sw/sdo_sb/targetcontent/bios/sysbios/6_35_01_29/exports/bios_6_35_01_29/docs/cdoc/ti/sysbios/timers/timer64/doc-files/TimerTables.html

Best,

Ashish

The confusing thing is SYSBIOS presents two different Timer modules to use.

1.  SYSBIOS -> Scheduling -> Timer.  This is the one that got added to our project with your code you suggested.

2.  SYSBIOS -> Target Specific Support -> C674 -> Timers -> Timer.  This is the one I have the question about.  Because we are using the C6748, should we use the Target Specific Timer, or just stay with the general Timer from SYSBIOS?  If the answer is stay with the general SYSBIOS Timer, then why is even the Target Specific stuff in there?

Thanks, Dean

Ashish or any other TI SYSBIOS expert, can you please answer my question about which Timer modules we should be using for the C6748?

Thanks, Dean

This question comes up a lot.

The 'portable' Timer module in 'ti.sysbios.hal.Timer' actually forwards all of its APIs and functionality to the device-specific Timer module.

The motivation for providing the portable Timer module is that applications or drivers that needs to run on various devices will not have to conditionally #include different Timer.h files or have conditional "xdc.useModule()" entries in their config files based on the target/device.

Alan

Hi Dean,

I see the following status for the bugs in this thread:

• SDOCM00100884 Add Timer Frequency Table to the cdoc (showing default frequency) for dmtimer, gptimer and Timer64 modules
  • still open
• SDOCM00100886 Update cdoc for intFreqs config parameter in timer64 module
  • resolved in SYS/BIOS 6.40.01.15

So, looks like the doc now shows you how to change it, but the default is still 24MHz.

Steve

Hi Dean,

Adding to Steve's post. I am not sure why the below bug is still open, but it has been fixed in SYS/BIOS 6.37+.

• SDOCM00100884 Add Timer Frequency Table to the cdoc (showing default frequency) for dmtimer, gptimer and Timer64 module

Also, I believe the intFreqs[] feature for changing each individual timer64 timer's frequency has been implemented in SYS/BIOS 6.37+.

Best,

Ashish

Hi Dean,

What you are seeing is expected, as the default value for the timer frequency wasn't changed.  Rather, the option to change the frequency (via the intFreqs[] array) was exposed.  So, you need to change it using the intFreqs[] array if your timer runs at a frequency other than the default.

Steve

Bump.  This needs to be fixed.