I2C stops working on nRF9160-DK board version 1.1.0 when SW9 is switched to non default 3V position

RE: I2C stops working on nRF9160-DK board version 1.1.0 when SW9 is switched to non default 3V position

Burt — Wed, 13 Mar 2024 18:28:11 GMT

Yep, exact same behavior as nRF9160!

RE: I2C stops working on nRF9160-DK board version 1.1.0 when SW9 is switched to non default 3V position

Burt — Tue, 12 Mar 2024 18:42:01 GMT

Thanks, Jonathan. Just for fun, I may try to wire up an nRF52840Dongle I have here to the Ynvisible display and see the results. A test of my soldering skills!

Burt

RE: I2C stops working on nRF9160-DK board version 1.1.0 when SW9 is switched to non default 3V position

JONATHAN LL — Tue, 12 Mar 2024 15:28:19 GMT

[quote user="Burt"]But just curious, does Nordic Semi produce any parts that use a different hardware TWIM?[/quote]

we currently do not.

Regards,
Jonathan

RE: I2C stops working on nRF9160-DK board version 1.1.0 when SW9 is switched to non default 3V position

Burt — Wed, 21 Feb 2024 15:05:46 GMT

Thanks, Jonathan. I experimented and found that my Ynvisible hardware worked when I dropped the Baudrate register to 0x17F0000; used a scope to see 93 kHz, not realizing that the Baudrate is linear. All good. But just curious, does Nordic Semi produce any parts that use a different hardware TWIM? I know that would not help me; I just wish the hardware could be set to 100 kHz and be compatible with Ynvisible because Arduino Atmel chips work that way. You know, something about the way clock stretching is done.

RE: I2C stops working on nRF9160-DK board version 1.1.0 when SW9 is switched to non default 3V position

JONATHAN LL — Wed, 21 Feb 2024 11:38:00 GMT

Hi Burt,

There is a older reply on a UART case but the formula is the same for TWI, https://devzone.nordicsemi.com/f/nordic-q-a/391/uart-baudrate-register-values/2046 .

The formula is: Baudrate = desired baudrate * 2^32 / 16000000

Regards,
Jonathan

RE: I2C stops working on nRF9160-DK board version 1.1.0 when SW9 is switched to non default 3V position

Burt — Sat, 17 Feb 2024 16:38:44 GMT

Hello DevZone, I am ready for a bit more help. The engineering team at Ynvisible recommended that I slow the I2C bus down from 100 kHz to 10 kHz. I did this using the Zephyr bitbang I2C software driver and I had SUCCESS. I would like to try this with a temporary hack to the hardware driver code in modules/hal/nordic/nrfx/mdk/nrf9160_bitfields.h: the line

#define TWIM_FREQUENCY_FREQUENCY_K100 (0x01980000UL) /*!< 100 kbps */

I would like to change the number for 0x019800000 to a number that will give a slightly slower bus. I would be grateful if you could provide me with a formula for choosing the value, given bus frequency as input. So I could try 95kHz, 90kHz,... to see how far down I have to go in order to have success. One of the hardware engineers must know a formula. I know it's a bit ugly but we want something that works. Thanks, please get back to me.

Burt

RE: I2C stops working on nRF9160-DK board version 1.1.0 when SW9 is switched to non default 3V position

Burt — Mon, 05 Feb 2024 07:23:21 GMT

That’s funny, I just assumed you were one of the Nordic folks. I guess our discussion should help them fill in more details. Thanks.

Burt

RE: I2C stops working on nRF9160-DK board version 1.1.0 when SW9 is switched to non default 3V position

Achim Kraus — Mon, 05 Feb 2024 07:15:53 GMT

Hi Burt,

I'm just an other user, which used the DK with i2C and 1.8V or 3.0V. In my experience, that worked quite well. But for more details about the nRF9160-DK i2c or expert questions, I'm the wrong ;-).

RE: I2C stops working on nRF9160-DK board version 1.1.0 when SW9 is switched to non default 3V position

Burt — Sun, 04 Feb 2024 20:27:17 GMT

Hello Achim,

I am getting a different result on the 0.9.0 nrf9160-DK: I do not get any I/O errors, regardless of the SW9 voltage setting. Oh, I am using pins P19 pins 9 (SDA) and 10 (SCL). They are marked P0.30 and P0.31. Note that on the 1.1.0 board this P19 is relabeled as P4 and still has P0.30 and P0.31. Although I do not get any I/O errors using the 0.9.0 board, many times the display does not change numbers (sequence -99...0...99 incrementing once every 5 seconds). Randomly it cooperates. That must be the lack of pull up resistors on that board.

At one point this morning I accidentally reverse powered the Ynvisible adapter board. I thought I had toasted it but then I tried it on my 5 Arduino boards, and it is fine, everywhere. It never fails to count there. But they did trick me on the Arduino DUE by moving the standard I2C port to different pins (looking carefully one sees that the "regular" pins are no longer SCL and SDA but are SCL1 and SDA1).

I see that the circuitry on the nRF9160-DK board changed for SDA and SCL between 0.9.0 and 1.1.0. I do not have a good understanding of the 1.1.0 circuitry although I tried to casually read the datasheet for the PCAL6408A. I half understand the circuitry: they added pullup resistors and an analog switch and the PCAL6408A.

I am still baffled why the 1.1.0 board works only with the low VDD of 1.8 volts. Please help me understand the circuitry to the level of detail required to understand what is going on. Thanks.

Burt

RE: I2C stops working on nRF9160-DK board version 1.1.0 when SW9 is switched to non default 3V position

Achim Kraus — Sun, 04 Feb 2024 17:24:36 GMT

Hi Burt,

> Now, before testing on the nRF9160 I had successfully tested on an Arduino board, using 3.3 volt power.

That's promising. So, which I/O pins on the nRF9160-DK are you using? Maybe you try, if a 10K pull-ups helps.

RE: I2C stops working on nRF9160-DK board version 1.1.0 when SW9 is switched to non default 3V position

Burt — Sun, 04 Feb 2024 15:49:34 GMT

Hello Achim,

Thank you for your quick reply. But I need more help! The e-paper itself may run at 1.5 volts, but I am using their test kit that has an I2C adapter and the instructions specify 3.3 volts: How to Set Up Ynvisible's Segment Display | Ynvisible. That link mentions an older kit that specified a 5-volt power connection. Now, before testing on the nRF9160 I had successfully tested on an Arduino board, using 3.3 volt power.

I had made one nRF9160DK error when I opened this ticket. I had programmed the nRF9160dk_nrf52840 to the hci_lpuart sample for some other work. But I used the Programmer to both realize this mistake and reprogram back to nrf9160_dk_board_controller_fw_2.0.1.hex. Reprogramming did not help.

Here is my program top level. The first number I try to display does appear, even though I cannot display more than that given the -EIO errors.

Can the board be damaged by programming hci_lpuart? If so, I'd better work with the supplier for money back.

I will have to try this using an older DK board (I have 0.9.0 and 0.8.3). And I may look around the house for other I2C devices and possibly try a small program for them.

I appreciate any more help, anything you can think of that might apply.

Best Regards,

Burt

RE: I2C stops working on nRF9160-DK board version 1.1.0 when SW9 is switched to non default 3V position

Achim Kraus — Sun, 04 Feb 2024 08:25:49 GMT

If you read the datasheets of the E-paper, you may get aware, that there are two versions, the old gen1 with 3v, and a new gen2 with 1.5V. If you operate a gen2 with 3V, then you're out of spec.

In my experience, the nRF9160-DK itself works well using i2c with either 1.8V or 3V, as long as the connected i2c device supports that as well. Sometimes you need to care, if a device uses different voltage levels for power supply and I/O, that's all in the datasheets.