nRF52840 (TWI) using Grove-LCD RGB Backlight V4.0

RE: nRF52840 (TWI) using Grove-LCD RGB Backlight V4.0

Radio — Tue, 11 Aug 2020 16:24:54 GMT

Thanks for the information.

RE: nRF52840 (TWI) using Grove-LCD RGB Backlight V4.0

ketiljo — Tue, 11 Aug 2020 06:41:12 GMT

It might happen, but it doesn't necessarily mean it's within spec, so strange things may happen. I suggest you get the HW correct first and tackle any SW issues afterwords.

RE: nRF52840 (TWI) using Grove-LCD RGB Backlight V4.0

Radio — Tue, 11 Aug 2020 05:46:24 GMT

Hi Ketiljo,

In my current setup 5V out from the DK is connected to the LCD. SDA/SCL out from the DK is 3.3V.

However, I am able to read the available I2C addresses. Is this possible to happen?

Thanks!

RE: nRF52840 (TWI) using Grove-LCD RGB Backlight V4.0

ketiljo — Mon, 10 Aug 2020 14:13:40 GMT

The display module needs 5V to operate the LCD, else the display pixels will not show. You need something like this: https://www.adafruit.com/product/757

RE: nRF52840 (TWI) using Grove-LCD RGB Backlight V4.0

Radio — Mon, 10 Aug 2020 13:58:52 GMT

Hi Ketiljo,

I tried using nRF twi_scnner example, to see the available i2c addresses. It is able to read and showing three addresses.

0x3E, 0x62, and 0x70. I was able to run this with 3.3 V as well.

I am not sure what is 0x70 is though. Seems like it is not a address belongs to Grove, as it is not a address belong to their parts according to this website: https://wiki.seeedstudio.com/I2C_And_I2C_Address_of_Seeed_Product/

I can debug the above code with 3.3 V as well. Except, when I connect to 3.3 V, I don't see the black pixels.

Thanks!

RE: nRF52840 (TWI) using Grove-LCD RGB Backlight V4.0

ketiljo — Mon, 10 Aug 2020 13:46:46 GMT

Looks like the display module is running on 5V. Then probably the I2C is also 5 V logic, which is not compatible with the max 3.6 V logic level of the nRF52 DK. You need a I2C level shifter between the two.