I haven't used it, but the Ultimate Breakout GPS looks to be a 3.3V device with 5V tolerant inputs.
https://www.adafruit.com/product/746
You can power it from 5V as it has a 3.3V regulator built-in, but you don't need to level shift the...
I was curious and have lots of test cases laying around, so I ran a few tests at132.9MHz as reported by the software using the PJRC PSRAM test combined with a simple Flash test that formats the Flash and writes/reads a file.
8MB APMemory =...
The 3144 Hall Effect sensor itself requires at least 4.5V power. Perhaps try powering the module from 5V and pull the output up to 3.3V as you have it for compatibility with the T4.0 to see if it helps to stabilize the readings.
You are asking too much from a 9V battery. Teensy 4.0 by itself draws about 100mA. 9V batterys have high internal resistance and are not designed to supply that much current.
Here is a website which shows some 9V batteries with 100mA (and...
Checking again... SerialFlashChip.cpp does not need any change for W25Q512.
Just to correct the first post of this thread, using 25Q512JVFM the ID is:
id[0]:239
id[1]:112
id[2]:32 (not "56" that I had read with a wrong connection..)