If you need high resolution differential timing, intel has some code here that claims accuracy down to the nanosecond. There's also a good discussion of general differential timing possibilities. Alright, after reading the Mach 3 documentation which is well-written, informative, and even funny , I think I see what is going on.
First, realize that there is a difference between having a user-space event trigger at a high frequency and having a kernel interrupt routine. Furthermore, operating systems use the local timers for the schedule, which decides when user programs can run, and typically the scheduler speed is not more than 1 kHz, therefore it's impossible to write a user-space program that responds faster than this.
However, in this case, you don't need to have complex user-space logic responding at that speed, since the goal is only to modulate an output pin at a high frequency in order to produce a PWM signal. It might be feasible to create a kernel interrupt handler for the APIC which has high priority and is triggered at high frequency, if it only does very simple things such as toggling an output pin on the parallel port.
So, if you wish to do this, I suggest you read up on kernel programming and using the APIC, and you might be achieve something useful to you. However, some words of advice:. Windows Multimedia Timers may be able to give you 1 ms. If you wrote your own driver however, you could grab ahold of HPET timers aren't available on all machines, but come with most newer ones and possibly the APIC timer not sure if this can give you kHz and get kHz from there..
This is pretty complex though so you'll have to do a lot more research. I tried to make it clear that I was not interested in measuring an elapsed time yet most of the responses pertained to exactly that. Apparently I did not adequately convey my point so I'll give it another try. The program that I referenced, Mach 3, generates a frequency of , when the user had selected ,, but the frequency is very stable. I mention that to illustrate that the accuracy of the actually time interval is not critical just as long as the error in the interval time is consistent.
The , frequency is emitted on a parallel port pin where it can be verified with a scope, which I have done. Other respondents somewhat understood what I wanted to accomplish but their example was to measure the number of Loops that could occur in a time period of 1 Second while admitting that the CPU cost would be unacceptable.
The general consensus was that what I'm wanting to do is not possible. For those that align with that opinion I would encourage you to Google Mach 3 CNC , download a free copy of the program and then install it. Run the program, use the tabs to navigate to the diagnostics page you will be able to see for yourself that it is in fact possible.
The program will initially open operating at the default frequency of 25kHz. Forums like this have a large number of post pertaining to this subject matter and the responses are, for the better part, the same as what I received. I've been working with a CNC router myself lately using a realtime linux kernel, the issue you're seeing is the lack of realtime preemption in windows xp.
I can't view the Mach3 stuff from here, but the only way it should be able to work is by using a "kernel level" driver in windows.
Writing some sort of driver to bypass windows default preemption model is your answer though, i would start by learning a bit about windows drivers and maybe looking at the realtime patches for the linux kernel for reference. A basic problem with using a PC for motion control, without dedicated hardware, is the data rate of the various outputs built in to most PC's. If your customers don't have the budget for the high end motion controller you mention, then they simply aren't going to have access to kHz signals.
The downside is the buffering will probably introduce some latency in the system, which may impact the performance closed loop control circuit with the control in software. Another downside is this limits your frequency options.
If the audio port is an option for you, then you don't need to worry about timing at all, Just make sure you set the frequency properly, and produce your signal as you would otherwise. If you need to use a digital signal, the parallel and serial ports work in a similar fashion , but at a lower maximum speed.
EDIT Hmm It seems parallel ports are a bit faster than they used to be. An enhanced parallel Port EPP capable machine can give you up to 2mbits of of binary bandwidth, which should be well within the reach of your goal. However, due to the way the parallel interface works, data speed is dependent on the peripheral, rather than some predefined buffer speed. Essentially, the peripheral acknowledges that it has recieved data, or that it is ready to send data, for each byte transferred.
Additionally, data cannot flow in both directions at the same time, data coming from the peripheral will cause the stream of data from the host PC to block. A possible way to circumvent that is to just arrange to have two parallel ports available, or arrange for the peripheral to limit its own data transmissions to every other cycle. Besides a few error states, the most useful interrupts are generated when the input or output FIFO's reach a certain level.
You can use this interrupt to write or read new data to the port. The threshold can be set to anywhere from 1 to 16 bytes.
You could do this almost as well in software using a QueryPerformanceCounter. It's not free, it's a commercial product. It's written to introduce realtime into Windows XP etc It has some very fast timers. You might be able to fake a soundcard DSP into doing something like this, but I wouldn't bet on it. Any timer you can build on windows that will run at the required speed is going to be CPU bound.
It's not that the compute CPU can't handle it, but you have to think about the rest of the moving parts on your computer. A few options may be to create a loop back plug for a serial port and then play with bit patterns and signaling types to get a fairly stable signal. But you will be much better served to either build or buy a digital control board that is made to control a CNC mill.
Oh, and telling people they are wrong instead of having a constructive comment I consider that the only way that currently good speeds can be achieved is through USB-type connections to the computer. Disclosure: Some of the links on this website are affiliate links. As an Amazon Associate I earn from qualifying purchases. This means that, at zero cost to you, I will earn an affiliate commission if you click through the link and finalize a purchase.
While waiting for my daughter at her hip-hop class, … » more. The folks at MyHeritage. Dossy's Blog Everything that comes out of Dossy, from the strange to the banal. From a Command Prompt: C Related posts: microsoft inbound connection limit nazi says: no connection for you! Chris Leckness spends a week with the Treo Filed Under: Geeking out. Comments Ash says. July 27, at pm. Dossy says.
Thanks for stopping by. Anonymous says. August 25, at pm. Philip says. This port is exclusively reserved by the Windows Time service. If you have a computer with multiple network adapters is multi-homed , you cannot enable the Windows Time service based on a network adapter.
You can use the command-line tool W32tm. Membership in the local Administrators group is required to run W32tm. This option might be used more than once. Computer names are separated by commas, with no spaces. The default value is 3. The allowed range is If not specified, the local computer will resynchronize.
Otherwise, wait for resynchronization to complete before returning. This is used for compatibility purposes. The default is 2 seconds. If not specified, the default is the local computer. When specifying multiple peers, this option must be enclosed in quotes.
This setting is only meaningful on domain controllers. YES : This computer is a reliable time service. NO : This computer is not a reliable time service. If not specified, the default value is the local computer. In verbose mode, display the undefined or unused setting too. Valid values are 0 to A range of numbers is valid, in addition to single numbers, such as ,, Value is for logging all information.
Set client to use two time servers To set a client computer to point to two different time servers, one named ntpserver. To configure a client computer that is currently synchronizing time using a manually-specified computer to synchronize time automatically from the AD domain hierarchy, run the following following:.
To check a client configuration from a Windows-based client computer that has a host name of contosoW1 , run the following command:. The output of this command displays a list of W32time configuration parameters that are set for the client. Windows Server has improved the time synchronization algorithms to align with RFC specifications. Therefore, if you want to set the local time client to point to multiple peers, we recommended that you prepare three or more different time servers.
If you have only two time servers, you should specify the Ntpserver UseAsFallbackOnly flag 0x2 to de-prioritize one of them. For example, if you want to prioritize ntpserver. Additionally, you can run the following command and read the value of NtpServer in the output:. In order for W32tm. Then, to adjust the computer clock by using the clock rate, W32tm. This algorithm varies depending on the version of Windows:. MaxAllowedPhaseOffset is configurable in the registry.
However, the registry parameter is measured in seconds instead of clock ticks. This command produces output that resembles the following. The output presents the poll interval in both clock ticks and in seconds.
The equations use the value measured in seconds the value in parentheses. The output presents the clock rate in seconds. To see the SystemClockRate value in clock ticks, use the following formula:.
For example, if SystemClockRate is 0. For full descriptions of the configurable parameters and their default values, see Config entries later in this article. The following examples show how to apply these calculations for Windows Server R2 and earlier versions. In this case, if you want to set the clock back slowly, you would also have to adjust the values of PhaseCorrectRate or UpdateInterval in the registry to make sure that the equation result is TRUE.
The Windows Time service stores a number of configuration properties as registry entries. It stores configuration information that the policies define in the Windows registry, and then uses those registry entries to configure the registry entries specific to the Windows Time service. As a result, the values defined by Group Policy overwrite any pre-existing values in the Windows Time service section of the registry.
Some of the preset GPO settings differ from the corresponding default Windows Time service registry entries. Windows loads these settings into the policy area of the registry under the following subkey:. Then Windows uses the policy settings to configure the related Windows Time service registry entries under the following subkey:.
The following table lists the policies that you can configure for the Windows Time service, and the registry subkeys that those policies affect. When you remove a Group Policy setting, Windows removes the corresponding entry from the policy area of the registry. This information is provided as a reference for use in troubleshooting and validation.
Windows registry keys are used by W32Time to store critical information. Don't change these values. Modifications to the registry are not validated by the registry editor or by Windows before they are applied. If the registry contains invalid values, Windows may experience unrecoverable errors. Some of the parameters in the registry are measured in clock ticks and some are measured in seconds. To convert the time from clock ticks to seconds, use these conversion factors:.
Note Zero is not a valid value for the FrequencyCorrectRate registry entry. HoldPeriod All versions Controls the period of time for which spike detection is disabled in order to bring the local clock into synchronization quickly. A spike is a time sample indicating that time is off a number of seconds, and is usually received after good time samples have been returned consistently. There's a possibility that Microsoft could block you from the server if you send too many requests in a short amount of time.
Not Helpful 0 Helpful 0. Include your email address to get a message when this question is answered. A synchronization interval of one day is usually enough for most users. However, if you need a highly accurate time and your clock drifts often, an hour should be suitable. Under no circumstances should you poll a time server more often than once every 15 minutes. Helpful 0 Not Helpful 0.
If your computer is not synchronizing at the correct time, you may need to tell the Time Service to use the SpecialPollInterval setting. See this link for instructions. Helpful 0 Not Helpful 1. Submit a Tip All tip submissions are carefully reviewed before being published. Keep in mind that it takes several seconds to synchronize the time.
So, do not make the interval one second. This will cause unnecessary load to your computer, as it will be constantly running the synchronization program. Helpful 1 Not Helpful 0. You Might Also Like How to. How to. Co-authors: Updated: May 5,
0コメント