Teensy 3.6 vs Teensy 3.2
- Thread starter Laki
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PaulStoffregen
Well-known member
Maybe you could be more specific about "really fast"?
Unless you write very inefficient code, both are capable of moving USB serial at ~1.1 Mbyte/sec (the limit imposed by the USB port at 12 Mbit/sec). Both are capable of 1000 HID events per second (the limit imposed by HID's use of USB interrupt transfer type).
So unless there's something more about your application, from only what you've said, I'd guess either will be more than fast enough since the speed is limited by the USB.
Unless you write very inefficient code, both are capable of moving USB serial at ~1.1 Mbyte/sec (the limit imposed by the USB port at 12 Mbit/sec). Both are capable of 1000 HID events per second (the limit imposed by HID's use of USB interrupt transfer type).
So unless there's something more about your application, from only what you've said, I'd guess either will be more than fast enough since the speed is limited by the USB.
GremlinWrangler
Well-known member
The raw speeds are as per the sales pages. For what you are trying to do the limits will be more about the HID performance which is pretty much fixed by the nature of the USB specification.
Suspect this will depend far more on how you package the data up and designing to maximise USB throughput than on the CPU horse power at the Teensy end. Basic maths on your 5ms indicates that a T3.2 will be running 480,000 instructions in that time which suggest CPU will not be the limit unless you are executing floating point or similar on the data going past.
Edit - go with Pauls answer seeing as he beat me to it. Possibly of interest https://forum.pjrc.com/threads/24277-teensy-3-0-USB-Serial-speed-at-7-5K-Bytes-sec
Suspect this will depend far more on how you package the data up and designing to maximise USB throughput than on the CPU horse power at the Teensy end. Basic maths on your 5ms indicates that a T3.2 will be running 480,000 instructions in that time which suggest CPU will not be the limit unless you are executing floating point or similar on the data going past.
Edit - go with Pauls answer seeing as he beat me to it. Possibly of interest https://forum.pjrc.com/threads/24277-teensy-3-0-USB-Serial-speed-at-7-5K-Bytes-sec
PaulStoffregen
Well-known member
Even Teensy LC would be able to do this at about the same speed. If this is all you need to do, there's no need to spend extra for a 3.2 or 3.6.
For Teensy's part in this system, you can expect an average of about 1 ms and a worst case of approx 2 ms. These times are pretty much entirely due to the USB protocol and how the USB host controller chip in your PC schedules the USB bandwidth.
Something to keep in mind is Teensy isn't the only part of this system. On the PC side, you've got 1 program sending bytes to the COM port and some other software responding to mouse clicks. Unless you've gone to very special steps to run these programs, they will probably run with the normal user level scheduling of whatever operating system you're using. If you're using Microsoft Windows, the OS scheduling latency can vary from almost zero to 16 ms. Obviously there's nothing Teensy can do about that... but I can at least mention it, so you can look into that part and hopefully achieve your low-latency goal.
For Teensy's part in this system, you can expect an average of about 1 ms and a worst case of approx 2 ms. These times are pretty much entirely due to the USB protocol and how the USB host controller chip in your PC schedules the USB bandwidth.
Something to keep in mind is Teensy isn't the only part of this system. On the PC side, you've got 1 program sending bytes to the COM port and some other software responding to mouse clicks. Unless you've gone to very special steps to run these programs, they will probably run with the normal user level scheduling of whatever operating system you're using. If you're using Microsoft Windows, the OS scheduling latency can vary from almost zero to 16 ms. Obviously there's nothing Teensy can do about that... but I can at least mention it, so you can look into that part and hopefully achieve your low-latency goal.
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