Quote from: bwims on Apr 08, 1974, 04:34 pmIt looks like robotshop is not dfrobot.No warning here, and the schematic has not changed...Bummer...Yes, robotshop is a distributor for various parts manufactured by others (DFRobot in this case makes the lcd shield). I've used them in the past rather than ordering straight from DFRobot because Robotshop is USA based and shipping times are much less. As I mentioned upthread, evidently robotshop hasn't changed the warning, but when I ordered the lcd shield in May, it was the fixed version where digital pin 10 does control the contrast.IIRC, you can't use servos and the lcd shield together on UNOs because the servo library disables PWM on pins 9 and 10.
It looks like robotshop is not dfrobot.No warning here, and the schematic has not changed...Bummer...
Hi, I'm curious about this.My understanding is that pin 10 would control the brightness on boards with this bug - just that it puts a high current on the pin with the danger of frying it. Have you done the test to see if the problem exists on your board, as described by the original poster?
Otherwise, I cannot see why DFRobot would not have updated their schematic. Could it be that you are just lucky?
Also, you say pin 10 controls the contrast - do you mean brightness? I thought a VR controlled the contrast?
HiIs it right to assume that if I can only see 1 resistor beside the transistor under the LCD that my board has the issue?
Will it be ok as long as I dont use D10 in my code for brightness?
This is really a non-issue.
It would have been nice if the resistor is on the transistor's base.
But even if it is not, you can still control the backlight via the pin (D10): first, clear D10. After that, if you wish to turn on the back light, turn D10 into an input - the pull-up resistor will now turn on the switch / led; if you wish to turn off the back light, turn D10 into an output - now, D10 will be cleared thus turning off the switch / led.If you do that in a timer, you can do software PWM and control the backlight brightness continuously.
There is also a software alternative which is to set the pin to input mode to turn the backlighton and to output and low to turn the LED off.
Do not set D10 to HIGH or use PWM on this shield unless you modify it.You can still control the backlight .First set D10 to LOW. (only need to that once)Then set the D10 to OUTPUT for off and INPUT for on.
But that is just my guess.
AVR's output, even in the push-pull mode, isn't a strong voltage source in that it has substantial output resistance. So even if you short the output pin (in a logic 1), you don't get much current (40-50ma maybe) out of it. The design here isn't a great design but it is not a deadly design either.
Stresses beyond those listed under "AbsoluteMaximum Ratings" may cause permanent dam-age to the device. This is a stress rating only andfunctional operation of the device at these orother conditions beyond those indicated in theoperational sections of this specification is notimplied. Exposure to absolute maximum ratingconditions for extended periods may affectdevice reliability.
2] The sum of all IOH, for ports B0 - B5, D5 - D7, ADC6, XTAL1, XTAL2 should not exceed 150 mA.
I measured 95ma being sourced from D10 when D10 is high.
AVR's output, even in the push-pull mode, isn't a strong voltage source in that it has substantial output resistance. So even if you short the output pin (in a logic 1), you don't get much current (40-50ma maybe) out of it.
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