TonyAme

Generally yes. However, many i2c devices these days can run on either 3.3 volts or 5 volts. You might want check if your device can run at 3.3v and eliminate the level shifting. In the past when I had devices that needed 5 volts, I would use...

Hello, Thanks for reading. Would I need to use a logic level shifter to convert the 5V logic levels (I2C) of the LCD's scl/sda lines to 3.3V in order not to damage the Teensy's scl/sda pins? Any recommendations for an easy to use Level Shifter...

In case anyone else has questions about using external pullup resistors for the sad/scl lines when using the Adaruit MPR121 capacitive touch board, I have discovered that they already have built-in 10k pullup resistors, as described here...

It depends on the specific device. Most should be fine with it. For safety I would power the device without connecting SCL/SDA to anything and measure them, to ensure the device does not have its own internal pull-ups to VCC (5V). If it doesn't...

thank you. right, i would connect the pullup resistors from sda/scl to the 3.3V. is it ok that the i2c parts are powered by 5V while also using pullups connected to 3.3V?

I would add external 3.3V pull-ups for any more than one device, assuming none of them incorporate their own pullups (and if they did, that they were not connected to 5V because the Teensy's not going to like being directly connected to those...)

I am using the Teensy 4.0 with two external I2c components. One is the Adafruit MPR121 capacitive touch sensor board and the other is an LCD. I am using Adafruit's library for the MPR121 cap touch board, which uses the "Wire" library which...

Thanks very much for the info, very appreciated.

Yes — you should use a high-impedance buffer or simple op-amp preamp before connecting the guitar to line-in, otherwise you’ll lose tone and level. A basic TL072 buffer circuit works fine for this kind of setup. Also seen similar DIY audio...

I would suggest putting a 3-position pin header for the display power, and use a 2-position shorted jumper to select between the two power choices. The middle pin of the 3-position pin header would be connected to the power input to the display...

I think that is actually a linear regulator, at any rate the power side of the schematic looks reasonable. I power my 4.0's in the same way. My only comment is the electrolytic cap: 470 nF or do you mean 470 uF? I would recommend the a latter.

Thanks very much for that insight. A better solution than what I had. Sincere Thanks. TonyAm

Yes, the schematic shows a linear regulator, but was thinking about using a buck converter instead. 470nF might have been a typo, I will check. Thank you for pointing that out!

Sincere thanks for reading. Would using a 9V to 5V buck converter be more suitable in my schematic? I'm using the Teensy 4.0 and the Audio board RevD2. Any recommendations for a proper buck converter? The headers marked U7, U8 are where I'll be...

Thanks very much for the great help on this, very much appreciated. TonyAm

Yes, AGND and GND can be connected. VGND (ground terminal of the headphone jack) and either GND or AGND must not be connected. When you install both T4.0+AudioBoard on your board, does the Teensy work fine for some time until the voltage...

Is it ok to connect AGND to GND the way I did in the schematic? Thanks.

Ok, when using the Teensy with an Audio Board like that, it has happened that parts from the underside of the Teensy touch parts of the Audio Board and SHORT OUT. That's one of the reasons why it's better to use tall plug and sockets for the...

Thank you. I did use the tall headers on the first board that I put together and has the same problem. I will investigate this possibility. Edit: Ok, when carefully inspecting the two boards nothing is contacting in a short, all separated...

Right, thank you. Here it is on top of the Audio Board Rev D from Amazon.

A photo showing the Teensy would be useful.

Hello, Thank you for reading. I bought a Teensy 4.0 and Audio Board Rev. D from Amazon and been having problems with my custom PCB audio circuit, whereas previously I did not. I noticed that on the Teensy 4.0 purchased from Amazon it had "NXP"...