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If you want to protect the 74HCT245 chip from the output wires accidentally touching +12V, you should add a schottky diode between each of the chip's pins and +5V. While my tests all had the zener diode too, that 2nd round showed the zener wasn't doing much, so just a 330 ohm resistor and a...

QNEthernet mimics the original Arduino Ethernet library API, so there's a chance the Websocket library might "just work". Might at least be worth a try. If it doesn't work, tell us about it here. Best to give exact code and steps to reproduce the problem.

Ok, I've put adjusting the CPU voltage on my high priority list for version 1.61.

Good, at least now you can be certain the Aliexpress vendor sent the model which needs 5V power. With the contrast pot, please understand it can be turned too far. If it is too much, you will always see all pixels on, even when text should be shown. On the power only test, usually the correct...

Serial8 and SPI hardware are independent. They should be usable together. There is no hardware limitation where these 2 peripherals somehow share an internal resource that would cause a conflict. From hardware point of view, they absolutely should not be any conflict. What's wrong on the...

Happy to report SparkFun's main Teensy page is now showing all 6 models of Teensy 4.1 in stock. :)

Quick update on my efforts to make the new bootloader handle this and other possible unexpected flash configurations. The big question is what actions can recover from all possible flash configurations. So far I have these 5 steps: Send quad mode 0xFF command (2 SPI clocks). If the flash is...

RAM1 is faster because it's connected by the "tightly coupled" buses. RAM2 connects by slower AXI bus. But RAM2 is cached, so for most access cache hits give the same speed. RAM2 is only slower for cache misses. How much difference that makes, if any, really depends on how your program uses...

I'm working on the next bootloader update, so it will be able to handle the powered down flash. Odds are good this will also handle the chip busy, as I'm the 0x99 reset command. If I have extra time I might try to build a test case...

After some experimenting, I came up with this simple program which doesn't require editing any core library files. I'm able to reproduce the problem with putting the flash chip into power down mode. But so far I can't get anything unusual with quad fast continuous mode. Have you see the...

I'm looking into the report of bootloader getting stuck, mentioned in msg #43 on the DMAChannels thread, linking here. So far I'm running the code from msg #26 (both the stuff copied to eeprom.c in core library, and the sketch in an IDE window). So far I've not looked deep. I've just...

2 blink error means communication problems between the bootloader chip and main processor. Usually this implies a hardware failure, like mechanical stress on the PCB caused either chip to sever from its pads. We've also seen cases where soldering leaves flux or other conductive residue which...

So for one final test, I reconnected to wire to Teensy 4.0 to see if it survives abuse with this circuit having only 330 + 22 ohms. I'm happy to report Teensy is working fine. The voltage while high is 3.409, not too bad. But you see Teensy isn't able to bring the pin lower than 0.56 volts...

Now the question is what happens if the circuit has a much lower resistor. It will protect less, but how much. Here's a quick repeat of the prior tests without Teensy connected. At the zener diode, now 4.082 volts. In other words, the zener is probably not doing much work here. And and...

I tried a few more resistors between Teensy and the zener diode. First 100 ohms, then 56 ohms, and finally only 22 ohms, which lets the LEDs work. Remember earlier how I said there were 4 ways to choose the parts. Hopefully all these photos can really show how useful a solderless breadboard...

Now for another test, do LEDs actually work. I'm sad to say, first result was no. The circuit seems to interfere with the signal too much. Probably the zener diode has too much capacitance and forms a low pass filter together with the first resistor.

Now for the moment of truth... I put the wire back in, so the circuit with 12 volts at the output is now connected to Teensy pin 13. I'm happy to report the Teensy 4.0 in this test is still working fine and running the LED blink program. When driving high, the voltage is 3.312. When driving...

Now for a test to see how this protects from 12 volts, first I removed the wire between Teensy and this circuit. Then I set my power supply to 12 volts and connected it to the output. Here's the voltage measured at the zener diode, which is after the first stage of protection. 4.77 volts...

Next I tried putting in a 1N4732A diode, rated at 4.7 volts. This zener diode has almost no interference with the signal. The output while logic high is 3.23 volts.

To demonstrate this 2.04 volt problem really is due to the zener diode starting to conduct way below its 3.3V rated voltage, here's the exact same test when I pull the zener diode. The output is 3.24.

To try to give you a useful example, I pulled out my draw of random zener diodes and a solderless breadboard. For a first attempt I found a 1N4728A zener (rated 3.3V) and a 1N5819 schottky, and two 330 ohm resistors. As a first test, I ran basic LED blink with the delays increase, so my...

I'm looking at your schematic. Fuses are not a good choice. By the time the fuse takes to "blow" (or increase in resistance for PTC self resetting type), the damage to Teensy will be long since done. Fuses are mainly used to prevent extreme overheating which can cause a fire. You really want...

FWIW, I don't do schematics either, even for fairly complicated stuff. Teensy 4.0, for example, only got a schematic after it was released.

Most optocouplers are too slow for WS2812 / WS2815 data. If you're going to go that route, you probably want a higher speed RF-based isolator, like ISO6420 or CMT8020N0 or similar. These isolators can also serve to convert logic levels. But the (presumed) problem remains that accidentally...

I've added this to my list of issues to investigate. At this moment I'm testing a T4 bootloader chip update, so I can't look at this or much of anything else until next week. While a bit embarrassing to admit, my gut feeling is this FIFO threshold setting goes all the way back to the earliest...

It Teensy is unpowered, the first of the 2-stage approach (msg #5) still works to limit the amount of work the other stage has to do. The first stage with zener diode doesn't depend on any power. The second stage does use diodes to divert current into the power supply. Indeed using schottky...

Use FLASHMEM on functions that aren't performance critical. That moves them completely out of RAM1 so they run directly from flash. The flash memory is slow, but it's cached, so you only suffer that slowness for cache misses.

Today I learned Apache web server configurable log format has an option to log the number of microseconds every request took to fulfill. I've added it to this forum server's config. Hopefully it'll make future automatic analyzing for performance impact possible.

Back in the early days of computers, when they had real hardware serial ports with 9 or 25 pin D-sub connectors, setting the baud rate in PC software actually did change hardware settings completely within the metal case of your PC. Now in these modern times of USB serial adapters, when you...

It's back in stock on SparkFun's website. https://www.sparkfun.com/teensy-4-1-without-ethernet-with-copy-protection.html

I'll answer about the protection circuitry. But please understand my reluctance to give answers that speculate about what actually went wrong with a system I haven't used and can't even really see. On the diode for the circuit in msg #5, you must use a zener diode. A regular diode will not...

FWIW, I looked again and sure enough, Arduino API issue #51 is still open. I must have been feeling a bit snarky nearly 5 years ago when I wrote that final comment with the horse graphic.

I must confess my low enthusiasm for more fiddling with the Arduino map() function. I have poured way too much time into map() over the years. Yes, replacing it with an all-float implementation might be "simpler". But the "simplest" course of action is to leave it alone. Today on Teensy 4 we...

Of course there's nothing in espressif code for this. When you connect one of those ESP boards to your PC, you have to set the serial baud rate in your PC software to match whatever baud rate the code running on the ESP32 uses. The espressif code doesn't have anything that affects the setting...

Looks like we're again being targeted by overly aggressive bots. If you experience the forum responding unusually slow or not at all, please make a note of the time and reply here when it's working again. A list of date, time, timezone of slowdowns really helps me to investigate. Since the...

Just to repeat, power the display with 5V power and leave the SDA and SCL pins unconnected. Turn the pot while watching the display. The pot will probably be able to turn about 240 to 270 degrees. Don't apply too much torque, as these tiny pots are not strong and yours is on the cheapest of...

It's this part on your photo from msg #31:

Also want to repeat my suggestion to use the known-good software setup from msg #19 and msg #26 until you have the hardware working. Thanks to @BriComp for preparing those 3 files. Trying to resolve a hardware problem using software that's also unknown to work makes everything more than twice...

It's definitely "popularity".

I hope you'll share photos and maybe even a video demo of the board when it's working?

SparkFun is manufacturing a large batch of Teensy 4.1 this week. Already a couple of the other Teensy 4.1 versions that were out of stock over the weekend have returned today. If the one you want is allowing backorders, now might be a good time to place your order.

You can also see a back side photo on SparkFun's website, which is the place you can actually buy. Just click a red "Purchase at SparkFun.com" button. There's also a larger back side photo on the Teensy 4.1 page if you scroll even farther to Test Points. I had meant to make the "Photos"...

Protecting against higher voltage usually involves a resistor and a diode. The diode limits voltage by directing current flow caused by the excess voltage. The resistor limits the amount of excess current the voltage can cause, which makes the diode's job possible. Here's one way you might...

Agree, it's really looking like your display hardware isn't working. One more possibility to add, maybe the contrast adjust pot on the back board is mis-adjusted so far that nothing can show in the display?

Since the problems you're experiencing (at least to the extent I can see) appear like the 5V display not turning on with 3.3V power, for your next step I would recommend attempting to power the display with 3.3V and then with 5V. You don't even need Teensy for this, if you have a power supply...

Good question. Maybe the I/O expander powers up but the display doesn't? Unfortunately I put all this stuff away and I'm moving on to final testing of bootloader update for compatibility for more flash memory chips, since people making DIY projects can't get the Winbond "M" flash chips right...

As a final test, I tried the code @BriComp posted in msg #19. I copied and pasted into 3 tabs in Arduino IDE, with care to name the 2 new tabs with the filenames he said. I hit just 1 small compile problem. The #include <LiquidCrystal_I2Cw2.h> lines needs to be #include...

Next I tried connecting the display power to 3.3V instead of 5V (using the exact same known-good example code from the previous test). I can confirm this display does *NOT* work with 3.3V power. The backlight turns on, but nothing appears on the screen. For another "nothing happens" test, I...

Amazon delivered the display. As a first test, I powered with 5 volts. Indeed it does have pullup resistors to 5V. A quick ohms measurement with power off shows 4.7K. I connected on a breadboard, with 5V power and adding 4.7K resistors to 3.3V. Quick voltage measurement without any...

Found this on Amazon. Look similar and only $10, so I ordered one to try. It should arrive Sunday evening. https://www.amazon.com/dp/B07S7PJYM6