I2C on AB02S - Newbie Qs

#1

Couple of real basic questions if anyone can help me.

  1. Do SDA and SCL require external pullups?

  2. What’s the current state of Wire.h? There seem to be several forks out there. Is there a best choice?

Thanks for any insights.

Art

#2

hi,

AB02S have two sets of IIC.

The first group of IIC has been connected to OLED display.And the pull-up resistor is connected by default(Need to pull the VEXT pin low).

The second group of IIC requires an external pull-up resistor.

#3

Sorry, I can’t undertand your meaning. Could you explain it more?

#4

Thank you, jasonXu. I’m attempting to use the SDA and SCL, and I’m seeing a device at 0x3C, which I suspect is the OLED, which I’m not using. Is it possible to attach an external sensor along with the OLED to the first I2C, or do I need to move the sensor to the second group?

It definitely helps to confirm that the first I2C group is pulled up to Vext internally, but that the second one needs external pull-ups. Thanks again!

#5

jasonXu,

There’s the Wire library from Arduino, and then there’s the one from the ASR650-x github site, which appears actually to be OneWire. There’s also HardWire and maybe some others. And I’ve seen threads where someone hacked their Wire.h, but I’m not sure which version they started with. So I guess I have two questions, really:

  1. Is the Wire library in the Heltec github current and correct?

  2. Is that the best Wire variant to use to connect to an external device?

Thanks!

#6

Oh, and another question: Using Wire, how do I declare that I’m using the second I2C pair and not the first? Thanks!

#7

Hi,

please refer the pciture:

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#8

All can, If you only use 1 set of IIC, you need to use polling(After using the first IIC device, you need to reselect the device slave address of the second group of IIC devices)

#9

The both answer are Yes.

#10

Thank you,JasonXu, for your patient tutoring!