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PaxInstruments / t400-electronics

Electronics for the Pax Instruments T400 temperature datalogger
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Switch bouncing #212

Closed charlespax closed 8 years ago

charlespax commented 9 years ago

The switches seem to bounce. See https://github.com/PaxInstruments/t400-firmware/issues/189 for background. Let's figure this out.

charlespax commented 9 years ago

Without any modification these are typical SW_A keypresses: ds2_quickprint20 ds2_quickprint21 ds2_quickprint22 ds2_quickprint23

I tossed a 0.1 uF cap between SW_A and GND. All presses look like this: ds2_quickprint24

Put a 0.1 uF cap on each switch.

charlespax commented 9 years ago

There is a problem during power on. There is a quick spike in power, probably transferring from bootloader to firmware. This is triggering the record function such that the device is already recording when the screen comes on.

In the screenshot below a 0.1 uF installed SW_B. The red area shows the device powering down. The green area is the device powering on. There's also a few button presses to the right. jh3ax

Here is the same process with a 0.47 uF cap installed. There is still a small spike, but it is not triggering the record function. 2e7wl

I think a good approach here is to try to fix this int he bootloader. Maybe that pin is being brought high or left floating.

charlespax commented 9 years ago

It's only causing a problems when connected to the Oscope.

charlespax commented 9 years ago

Okay. I have to add caps to between each switch and GND. Populate the 10 pullup resistors. Otherwise the two bootloader delay buttons are close to ground and the device will delay.

charlespax commented 8 years ago

I have put the latest revision on the scope and have not seen this issue. I think maybe there was either a software problem of the issue was due to the soft power logic circuit, which has been changed. Closing issue.