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jasonacox / TM1637TinyDisplay

Arduino library to display numbers and text on a 4 and 6 digit 7-segment TM1637 display modules.
GNU Lesser General Public License v3.0
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superfuous delay #4

Open nerdralph opened 3 years ago

nerdralph commented 3 years ago

Only one delay per clock phase is needed, so the one on line 538 can be deleted. https://github.com/jasonacox/TM1637TinyDisplay/blob/master/TM1637TinyDisplay.cpp#L538 Keep the delay on line 546.

Also the default of 100us seems excessive. The datasheet v2.4 lists 500kHz for Fmax, which means 1us per clock phase. I'd suggest a default bit delay value of around 5us, which would still leave a large safety margin.

jasonacox commented 3 years ago

That makes sense, but when I drop the bitdelay to 5 or 10us, the Arduino Uno is unable to drive the display. When I have more time, I'll investigate.

nerdralph commented 3 years ago

Earlier today I hooked my scope up and found the rise time to 3V is nearly 10us with my module. It has 10k pullups. The datasheet example circuit has 100pF caps, but the module must be using 1n. I have been modifying my TM1638 library for the 1637. I've avoided using delays by polling the clk and dio lines when they get pulled high.

On Thu, Nov 19, 2020, 00:55 Jason Cox notifications@github.com wrote:

That makes sense, but when I drop the bitdelay to 5 or 10us, the Arduino Uno is unable to drive the display. When I have more time, I'll investigate.

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jasonacox commented 3 years ago

I'm impressed! Makes sense. I've seen a few other TM1637 libraries that use aggressive timing that caused stability issues over time for my project on some modules I use. I may have over engineered the delays, but they are stable. I'll revisit when I get time. Thanks for all the feedback and PRs!