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PaxInstruments / t400-electronics

Electronics for the Pax Instruments T400 temperature datalogger
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System does not power down #199

Closed charlespax closed 8 years ago

charlespax commented 8 years ago

The version 0.13 PCB I have does not stay powered down. When the unit is on I press the power button. Then the LCD clears and the backlight turns off. Then data appears on the screen again and the backlight is off. The system still reads and displays temperature data and graphs.

The system appears to not reset. The data on the screen is persistent.

charlespax commented 8 years ago

On 0.13 PWR_ONOFF is connected to PD5, which is TX LED. I think the issue may be related to that. On 0.12 nothing was connected to this pin. We may need to change something in the bootloader to use the TX LED pin. However, on 0.12-mod PWR_ONOFF is connected to PD5, so this is probably not the issue.

Changes from 0.12 to 0.13:

This fuse and test point were removed. screen shot 2015-10-04 at 12 35 38

This resistor was added. In 0.12-mod we're using 4.7k while 0.13 has 10k. Swap out the values and see what happens. UPDATE: The 0.13 sample I have already has a 4.7k resistor. The problem is not here. screen shot 2015-10-04 at 12 38 11

Pull-up resistors were depopulated, internal ones used instead. We can try populating them again to test.

charlespax commented 8 years ago

Just a bad solder joint between the QFN ATmega32U4 and the PCB. I tossed a QTFP package on there and all is well.