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@PaulS @KenHahn Are those version of Teensy you sell (with the headers or with the headers+ethernet) the secure Teensy variant? That's what I'd need. I didn't see it mentioned, but perhaps I missed it.

This is all AMAZING info, really really appreciate it. Would love to hear more, if anyone has stuff to share. Really helpful. Thank you.

Delayed thanks for all this incredible information!

As I'm working through my prototype, I'm starting to consider how a hobby product with Teensy on a custom pCB could get manufactured. I've order PCBs from JLCPCB with success, but I'm not sure how the complexity of acquiring Teensy's would work or how they would mount them. If I go to...

If an interrupt occurs during a period where interrupts are disabled, will it be acted upon immediately when interrupts are enabled? Or is it lost? I suppose this comes down to whether they are edge triggered or level triggered. Example: 1. Millisecond timer interrupt occurs 2. Interrupts...

I read elsewhere than an interrupt takes around 240ns give or take based on cpu speed. Is that right? That’s functional breaking random delay for me. I completely understand many situations wouldn’t care at all about this. I could try and keep interrupts off almost all the time and enable...

Thanks! That would seem to mean that disabling then systick_isr (not sure how) would allow me to keep interrupts enabled but avoid any periodic ones, while keeping the automatic firmware download operational. I believe USB serial / automatic firmware download doesn't require random/periodic...

Thanks for the reply. The good news, for me, is that I don't use mills() or delay() and don't need serial. So I'm wondering what other surprises are out there...

Theoritical and kind of real world question. What harm is there in disabling interrupts in setup() and leaving them off? Obviously this prevents functions from running that use interrupts. But is there anything about the Teensy 4.1 that demands interrupts are enabled? Is there a list of...

Appreciate the insights! I've got a bit of a pin problem so I'm looking into other approaches for the short term (may adjust my PCB longer term if it's needed). @Paul shared some great info about Ethernet in a different thread I started. It was here...

Thanks. I wondered about the mapping of Teensy serial names to UARTs. And based on that info, Pin 4 isn't an option.

Interesting! To clarify, using the ARM_DWT_CYCCNT will always give the real info. The "probably not to trust" was about expectations based on C code and the compiler?

This is amazing. Thank you! I don't suppose there's a way to do this with Pin 4? My setup currently is using Pin 1 -- but I can change that if needed! -- Altan

Yes, I meant the transmit routine must be no more than 250 ns. Thanks for thinking about my problem and asking related interesting questions.

It's the 2.3.2 IDE. I'm going to give TyCommnader a shot.

Yes. It's the dev/cu.usbmodemXXXXXXX (Teensy 4.1). At least I think that's what you were asking?

I'm looking into running Ethernet directly but I cannot find the right interfaces. I've looked at FNET. I've looked at NativeEthernet. But I don't see anything like a Linux net_device. I did find fnet_return_t fnet_eth_phy_write(fnet_netif_desc_t netif_desc, fnet_uint32_t reg_addr...

I'm working on a project with Teensy 4.1. It's very (very!) timing centric and I've got it working. I need to communicate to an external device using whatever method/protocol is best, but "easy" things like Serial take way too time. I'm looking to send bytes per second, nothing huge! For...

Your post came in while I was writing the other. Thanks -- I was wondering if it's the IDE. I'm running on a Mac (older Intel). Any recommendations for a solid serial read/write program?

Thanks. I'd experimented with that delay -- didn't know why it was there. Good to know! Alas, that hasn't fixed my problem. Does the Teensy USB code require anything to work? For example, interrupts must be enabled? Would doing a delay(99999); after some serial operations cause a problem?

Thank you. With your info, I can see the function static inline void delayNanoseconds(uint32_t nsec) { uint32_t begin = ARM_DWT_CYCCNT; uint32_t cycles = ((F_CPU_ACTUAL>>16) * nsec) / (1000000000UL>>16); while (ARM_DWT_CYCCNT - begin < cycles) ; // wait } Uses F_CPU_ACTUAL so...

I've found that I often need to physically power cycle my Teensy to get USB serial logs. I'm using the Arduino IDE. Has anyone run into this? 100% of the time I'll get output if I power cycle, much of the time I'll get no output if I just upload new firmware to the Teensy. Any tips or best...

Following up with a clarification about delayNanoseconds --- Does delayNanoseconds adapt for a different CPU speed? For example, perhaps it's coded to work at 600 MHz but not at 912 MHz. I asked because when running at 912 MHz, I noticed Serial.println(F_CPU); Displays 600000000.

Oh, do I need this in setup still? ARM_DEMCR |= ARM_DEMCR_TRCENA; ARM_DWT_CTRL |= ARM_DWT_CTRL_CYCCNTENA Saw that in another post

Perfect, simple, thanks!

Thanks. I'm away from my Teensy at the moment but did some googling. Does this seem to be an accurate way to use the DWT? https://mcuoneclipse.com/2017/01/30/cycle-counting-on-arm-cortex-m-with-dwt/ Summary: uint32_t cycles; /* number of cycles */ KIN1_InitCycleCounter(); /* enable DWT...

For a Teensy 4.1 with Arduino --- I've got some situations where I need to do 10s of nanosecond delays. I've found the delayNanoseconds function, but the documentation is not detailed. Is there a location with hard specifics on this functions operation? I know from the Teensy page it's...

Thanks for the useful replies. So much to learn.

Hey. I'm new to Teensy and using some code that accesses GPIO9_DR. Using the Arduino IDE, I'd like to ensure the definition includes volatile so things like while ( (GPIO9_DR&0x80000000) != 0) {} Don't get optimized out. I've been unable to find the definition of GPIO9_DR to answer this...