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Topic: Stronger internal pull-up resistor  (Read 3298 times) previous topic - next topic


Dear developers,

I wonder could we revise (or why don't we) to use stronger pull-up internal resistors? For example, 10k-12k ones. They are included in Wemos D1 mini. Very convenient. You can combine two to get 5-6k pull up.

The 30-50k ones in current Arduino design seems not very useful ...

Thank you again for providing Arduino. Needless to say, it is amazing! :)



Mar 16, 2018, 08:42 pm Last Edit: Mar 16, 2018, 08:43 pm by Delta_G
You're talking to the wrong people.  That is a property of the chip.  You'd have to bring that up with the AVR folks. 

This is like calling up Ford and telling them that you think the speed limits should be higher so you can drive faster. 
|| | ||| | || | ||  ~Woodstock

Please do not PM with technical questions or comments.  Keep Arduino stuff out on the boards where it belongs.


@Delta_G Thanks for the reply. You mean the internal pull ups are in ATMega328? I don't think that's a problem. Wemos D1 mini has pull ups on their boards, not the ESP8266 chips. Please see schematic here.

Adding two 10-12k pull-up resistors on Arduino boards should be fairly simple. There must be other reasons not doing this.


The pullups on the Wemos board are on pins that have a dedicated bootup function, vaguely similar to the 10k pullup than an AVR Arduino has on RESET.  They're not needed, or useful, on an AVR arduino because the way the bootloader works is differently.  (pulling GPIO0 low during reset causes the chip to boot from either onboard flash or SD card, depending on GPIO2.  Having both pins high at reset (as cause the by pullups) makes the chip boot from internal flash.)

I don't see why you think the ~50k internal pullups are "not very useful", nor why 10-12k would be "more useful", nor how the pullups (r10 and r11, right?) on the Wemos board can be 'combined"...

Are you talking specifically about using pins for I2C?   The AVR Arduinos have hardware I2C support, but those pins can't have pullups by default because they're also analog inputs...


Mar 17, 2018, 05:57 am Last Edit: Mar 17, 2018, 06:05 am by liuyiar
Thank you for the thorough reply. I am still beginner to arduino.

I recently get into sensors. Both DS18b20 and DHT22 require a 4.7k pull up resistor. But using D1 mini, I don't need one. It is very neat. (I am aware of the article that with library code change you can save that pull up resistor also with arduino.

Combining 2 pull up is easy, just connect the two pin (D3 and D4), but only read from one. So you can get 5k pull up from two 10k. I got this idea from the comments of the same article I mentioned above. (First comment by AndrewN41)


Mar 17, 2018, 06:55 am Last Edit: Mar 17, 2018, 11:15 pm by westfw Reason: Add synonyms for I2C.
Yeah; that's I2C (aka IIC, I2C, TWI)- widely used for sensors...  Pretty much required on a module like the ESP-1 with it's few pins, but not one of the original design goals for Arduino.   A lot of the sensor modules you can get will have pull-up resistors built in...

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