When I connect a 6V external power supply to the V_BATT JST connector with no USB serial cable connected the Teensy will not start because there is no voltage on VIN (LED off). It can’t be reset/rebooted either.
If I now connect the USB cable (with external 6V power still connected at the JST) the VIN LED comes on, and teensy can be reset/rebooted and runs normally.
How can I run the micromod teensy with external power only (i.e. with no USB Serial connection) ?
In other words how to get voltage to VIN without Serial connection? (since the Teensy Processor depends on VIN)
My new Sparkfun LiPo finally arrived, and it powers the boards no problem. The LiPo output voltage was about 3.9V under load, so I also tested using a 4V external power source and it also works fine .
In the meantime I had powered the board up using 5V with this USB-C Breakout and it works fine, although the 5V MEAS point was only 4.5V (on main double) so I upped the power to 5.5V and all works well.
I only just noticed the MEAS cut point on the Teensy processor schematic with this note: “Cut to separate VIN from VUSB to measure current or if using battery or external power”. So I cut it and repeated all the testing above, but it made no difference at all. Maybe that was why 6V input didn’t work? Will test that later.