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sparkfun / SparkFun_Artemis

World's first open source hardware module using a Cortex-M4F capable of running TensorFlow models and Arduino sketches..
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Negative Voltage on Boot Pin #7

Open derekpickell opened 2 years ago

derekpickell commented 2 years ago

Hello,

Let me know if this is not the best place for this question and I will move it! Haven't gotten any feedback on the sparkfun forum so thought I should try here:

I noticed that the bootloader circuit temporarily drives the BOOT pin to -3.3V. Nowhere in the Apollo3 datasheet do I see any mention of being able to expose pins to negative voltage, and yet the boards seem to work fine! Just looking for confirmation that this is OK. Thank you!

nseidle commented 2 years ago

RedBoard-Artemis bootloader circuit:

image

Can you share a screenshot of the measurements you took? I remember doing the testing of the BL circuit and I never saw a negative voltage.

derekpickell commented 2 years ago

Here's how I setup my breadboard:

Screen Shot 2022-01-19 at 12 31 57 PM

Since I'm planning on uploading code only via a USB to Serial converter, I haven't included the DTR bus (although it's the same circuit), and the RESET is represented by the switch.

Here's the oscilloscope photo: the negative spike is when I manually ground RESET, and the positive is when I unground it. IMG_9152

Really appreciate the help!