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Author Topic: VCP driver on macOS 11  (Read 16553 times)

scotttmiller

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Re: VCP driver on macOS 11
« Reply #45 on: September 17, 2021, 11:58:11 AM »

Hello.  My name is Scott Miller and I am a BCI researcher.  I too am experiencing severe latency issues with the VCP driver on macOS 11.  I am using a MacBook Pro M1 running the latest version of Big Sur.

I read this entire thread and several others blog threads across the internet.  I emailed and spoke with Cameron from FTDI tech support in Oregon.  Cameron was very helpful.  He let me know that the latest 1.4.7 driver runs on both x86_64 and arm64.  I tried modding the 1.4.7 driver on my M1 but ran into the same code signing issues described by others in this thread.

Cameron also reached out to the FTDI team in the UK on my behalf.  That team replied with some links which talk about how to build my own driver, but that's not very useful to me at this point in time.

I also tried calling tech support in Glasgow, during normal working hours in GMT, but was unable to reach anyone at all.  The voice mailboxes are all full, and not even an operator answered my calls.  I tried repeatedly.

I suspect that FTDI is for some reason unable to obtain a DriverKit entitlement from Apple.  Is that the case?  Has FTDI made any progress on this issue?
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Re: VCP driver on macOS 11
« Reply #46 on: September 17, 2021, 02:50:05 PM »

Hello Scott,

Thank you for your question.

I would like to apologise that you haven't be able to contact any via phone in the UK office, unfortunately we are still working form home currently.

We are currently investigating how to generate a codeless .dext wrapper for any Info.plist modifications which might be required by an end user.
Is this what you are trying to achieve?

Could you describe the latency issues you are seeing?

Hello.  My name is Scott Miller and I am a BCI researcher.  I too am experiencing severe latency issues with the VCP driver on macOS 11.  I am using a MacBook Pro M1 running the latest version of Big Sur.

I read this entire thread and several others blog threads across the internet.  I emailed and spoke with Cameron from FTDI tech support in Oregon.  Cameron was very helpful.  He let me know that the latest 1.4.7 driver runs on both x86_64 and arm64.  I tried modding the 1.4.7 driver on my M1 but ran into the same code signing issues described by others in this thread.

Cameron also reached out to the FTDI team in the UK on my behalf.  That team replied with some links which talk about how to build my own driver, but that's not very useful to me at this point in time.

I also tried calling tech support in Glasgow, during normal working hours in GMT, but was unable to reach anyone at all.  The voice mailboxes are all full, and not even an operator answered my calls.  I tried repeatedly.

I suspect that FTDI is for some reason unable to obtain a DriverKit entitlement from Apple.  Is that the case?  Has FTDI made any progress on this issue?

Best Regards,
FTDI Community.
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scotttmiller

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Re: VCP driver on macOS 11
« Reply #47 on: September 17, 2021, 05:17:52 PM »

Yes I am trying to modify the Info.plist to adjust the latency and buffer settings, because I am experiencing extreme jitter in the timestamp intervals.  The issue is so severe that unless I can correct it, I cannot use the FTDI chip for my experiments.

My teammate is using the same chip on his older, Intel-based MacBook Pro.  He is also running the latest version of Big Sur.  He tried the unmodified 1.4.7 driver, and a modified 2.4.4 driver.  The unmodified 1.4.7 provides smoother streaming with less jitter than the modified 2.4.4, but it's still not good enough for our experiments.

The following are the settings he added to the Info.plist of the 2.4.4 driver:

  <dict>
    <key>InBufferSize</key>
    <integer>128</integer>
    <key>LatencyTimer</key>
    <integer>24</integer>
  </dict>

Can you recommend a different driver or different modifications for him?

--Scott
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Re: VCP driver on macOS 11
« Reply #48 on: September 20, 2021, 02:12:53 PM »

Hello Scott,

Thank you for the details.
The Latency timer and buffer settings are the correct settings to alter in this case.

However as I'm sure you have noticed performance on different machines can vary, this is due to the inherent nature of USB.

USB products can’t reliably be used in real-time applications with time interval resolution guarantees.

Sometimes the behaviour of USB can be a problem and applications cannot be guaranteed throughput.
If there is more USB traffic then the OS and USB have to schedule the communication with each of the USB devices.
It’s highly dependent on the OS and USB Host and is out with our control.

You could take a look at the following App notes:

Data Throughput, Latency & Handshaking
Optimising D2XX Data Throughput

These apply to all of our USB products.

The latency timer can only be set to 1ms minimum for our High Speed USB products and nothing less, and 2ms for our Full Speed USB products (like FT232R inside the USB-RS485-WE cable).

Best Regards.
FTDI Community
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scotttmiller

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Re: VCP driver on macOS 11
« Reply #49 on: September 22, 2021, 12:08:53 PM »

Thanks for the docs.   The VCP doc is informative, but it does not contain instructions for MacOS.  Can you please also send me instructions for reconfiguring your VCP driver on MacOS.
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Re: VCP driver on macOS 11
« Reply #50 on: September 22, 2021, 03:41:41 PM »

Hello,

Unfortunately we currently only have instructions for the previous .kext version of the driver:
https://ftdichip.com/wp-content/uploads/2020/08/TN_105-Adding-Support-for-New-FTDI-Devices-to-Mac-Driver.pdf

The edits to the info.plist would remain the same in terms of the latency timer and inbuffersize attributes, however Apple stipulating a codeless .dext approach for modifying drivers in macOS 11. The driver team are currently looking into the best way to produce a codeless .dext.

Best Regards,
FTDI Community
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scotttmiller

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Re: VCP driver on macOS 11
« Reply #51 on: September 27, 2021, 01:33:07 AM »

Thanks again! That is indeed a useful doc.  What is the latest version of MacOS for which those instructions are valid?
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Re: VCP driver on macOS 11
« Reply #52 on: September 27, 2021, 01:47:33 PM »

Hello,

That would be the last version of macOS to support .kext drivers, this would be 10.15, but there is an extra notarization step for .kext drivers required by Apple in 10.15, that is not noted in that document. As such it would be safe to assume these instructions work up for drivers up till macOS 10.14.

Best Regards,
FTDI Community
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