In search of Teensy 3.2, Can anyone help?

[jmoore]

Hey, all. I'm a ham radio operator working on a project that automatically tunes a magnetic loop antenna based on this design.

I've run into a roadblock in the project as it is based around a Teensy 3.2. I've assembled all the other parts but just needing to source the Teensy. Seems like the 2023 availability is a bit iffy.

Would anyone happen to have 1 or 2 extra Teensy 3.2 that you would be willing to spare?

-Jared NØOG

[mborgerson]

Hey, all. I'm a ham radio operator working on a project that automatically tunes a magnetic loop antenna based on this design.

I've run into a roadblock in the project as it is based around a Teensy 3.2. I've assembled all the other parts but just needing to source the Teensy. Seems like the 2023 availability is a bit iffy.

Would anyone happen to have 1 or 2 extra Teensy 3.2 that you would be willing to spare?

-Jared NØOG

Have you considered adapting your project to use the T4.0? Unless you require the touch input or something specific to the T3.2 ADC, you should be able to plug a T4.0 into the T3.2 socket and recompile your software. You could run the T4.0 at a reduced clock rate to conserve power without much risk of overloading the CPU.

[MichaelMeissner]

Have you considered adapting your project to use the T4.0? Unless you require the touch input or something specific to the T3.2 ADC, you should be able to plug a T4.0 into the T3.2 socket and recompile your software. You could run the T4.0 at a reduced clock rate to conserve power without much risk of overloading the CPU.

Not quite. It depends on what you do. Many programs will work fine, but others won't. I wrote the following pages to look at the differences:

• Unofficial Teensy Wiki, teensy differences: https://github.com/TeensyUser/doc/wi...-Compatibility
• Goggle spreadsheet comparing the pinouts of all 3.x, 4.x, and LC Teensies: https://docs.google.com/spreadsheets...it?usp=sharing

Basically, if you use these features, you need to redesign things:

• Using pin A14 for producing sound via a DAC (digital to analog converter);
• The I2S support uses completely different pins, which means you need a revision C audio adapter for Teensy 3.x and a revision D audio adapter for Teensy 4.x;
• Relying on digitial pins getting 5v signals without burning out the pin or the Teensy (including using 5v I2C devices without a voltage converter);
• Using touch pins;
• Using a serial UART other than Serial1;
• Remapping the SPI pins (needed for the revision C audio shield);
• Using the optimized display drivers (you can still use the drivers on the Teensy 4.x, but the special support to optimize the display if the CS and DC were among some special pins is not used, so it may be slower); (and)
• Using the pads underneath the Teensy 3.2 (there are extended pads in the Teensy 4.0 and more pins in the Teensy 4.1, but they do have different pin assignments).

[BriComp]

I agree @MichaelMeissner but if you look at @jmoore's basic design (see post #1) there does not seem to be any reason why a T4.0 might not work.
He would have to make sure non of the T4.0 inputs were more than 3.3V.

[mborgerson]

I agree @MichaelMeissner but if you look at @jmoore's basic design (see post #1) there does not seem to be any reason why a T4.0 might not work.
He would have to make sure non of the T4.0 inputs were more than 3.3V.

There are a couple of changes that should be made to ensure 3.3V compatibility:

1. D2 and D3, the 4.7V zener diodes in the input limiter to the analog pins should be changed to values below 3.3V

2. The encoder input should either be changed to 3.3 V or appropriate resistors added in parallel to C23 and C24 to divide down the encoder outputs to 3.3V maximum.

3. If the stepper drivers will accept 3.3V as the logic supply, that should be done to ensure clean transitions at the inputs. The A4975 wants 4.5V minimum for VCC. The alternate DRV8825 seems to be designed with 3.3V systems in mind.

4. The radios connected to TX1 and RX1 need to work with 3.3V drive. I suppose that's been considered as the T3.2 has 3.3V drive, but also 5V-tolerant inputs.

It does seem that this project could be adapted to use the T4.0. The difference in the ADC systems may require some resistor changes and program changes, but all the necessary pins are available for
analog inputs A8, A9, A10, and A11. The latter two require connections on the back of the board--as indicated on the schematic.