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Houston, we have a problem: UART port SimpleBCG 8bit: pullup current too high (27mA) on
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Used board is SimpleBCG 8bit (Unfourtunately I have not found any schematics)
Measurements have shown, that pullup current is too high on a Rx (Tx) pins on UART port.
Therefore I can not use my Arduino Due board for controlling gimbal through UART (Processor's pin pullup is max 6mA-9mA).
Arduido Uno can bearely handle this (but for now it works): Atmega 328P pin pullup is 20mA.
What to do? Is it known problem? Is there some fix from schematics?
I tried different firmwares „SimpleBGC 2.2 b2“ and „SimpleBGC 2.40 b7“. On both cases, I could measure current 27mA.
Current is so high, that even white LED is bright as hell:
https://www.dropbox.com/s/kannqp1ojwau6l9/bright_as_hell.jpg?dl=0
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I checked that Arduino Examples were made on Arduino Pro Mini, which runs on ATmega328 (page 303 on http://www.atmel.com/Images/Atmel-8271-8-bit-AVR-Microcontroller-ATmega48A-48PA-88A-88PA-168A-168PA-328-328P_datasheet.pdf) there is said, that DC Current per I/O Pin is 40.0mA.
So that's why on Your board it works. -
Input resistance of Rx-pin is too high. There won't such a large current.
So you may connect your "Uno" directly with the gimbal controller. -
If you still doubt, just put 1k resistor serial into the line.
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Well I measured that current on rx pin but arduino due can't drive so much current. You think that 1k resistor really help? For due the current should not be larger than 6mA.
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Please have a look on this picture, I could not explain better
1) Is it software problem - rx pin is set in software to "pull-up high" ?
2) Bad design problem ?
www.dropbox.com/s/btal73q1g6n60o0/current_correct.png?dl=0
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Sorry, bad attachment:
www.dropbox.com/s/hbc22q4x3oofa27/current_correct.png?dl=0
or here:
https://www.dropbox.com/s/hbc22q4x3oofa27/current_correct.png?dl=1
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