Pull down SDA pin i2c

RE: Pull down SDA pin i2c

Vidar Berg — Thu, 10 Nov 2022 09:45:18 GMT

Hi,

Can you turn on logging to see what the error is?

RE: Pull down SDA pin i2c

Hkhan7861 — Wed, 09 Nov 2022 14:18:34 GMT

This has helped! Am now seeing an output when the program starts as well as the drop of output on the SDA line when writing to the i2c2 . However, the write function still returning an error value. Other than the slave address or device function code being incorrect, are there any other reasons for the function to fail?

RE: Pull down SDA pin i2c

Vidar Berg — Wed, 09 Nov 2022 10:05:41 GMT

It seems like you don't have external pull-ups on the SDA and SCL lines as you measure 0 V on both . In that case, you will need to enable the internal pull-up resistors by adding the bias-pull-up property to your pin assignment in the device tree.

 &pinctrl {
	i2c2_default: i2c2_default {
		group1 {
			psels = <NRF_PSEL(TWIM_SDA, 0, 30)>,
				<NRF_PSEL(TWIM_SCL, 0, 31)>;
				bias-pull-up;
		};
	};

	i2c2_sleep: i2c2_sleep {
		group1 {
			psels = <NRF_PSEL(TWIM_SDA, 0, 30)>,
				<NRF_PSEL(TWIM_SCL, 0, 31)>;
			low-power-enable;
		};
	};

};

RE: Pull down SDA pin i2c

Hkhan7861 — Wed, 09 Nov 2022 09:19:55 GMT

My code is as follows:

main.c

#include 	<zephyr/zephyr.h>
#include 	<drivers/i2c.h>
#include	<stdio.h>
#include 	<nrfx_twim.h>
#include 	<C:\nordicsemi\v2.1.1\modules\hal\nordic\nrfx\hal\nrf_gpio.h>
#include 	<hal/nrf_twim.h>





/** I2C address to be used for ST25DV Data accesses. */
#define ST25DV_ADDR_DATA_I2C                 0x53
/** I2C address to be used for ST25DV System accesses. */
#define ST25DV_ADDR_SYST_I2C                 0x57


void Delay(int n)
{
   int c, d;
   
   for (c = 1; c <= n; c++)
       for (d = 1; d <= n; d++)
       {}
       
   return 0;
}



void main(void)
{   
	// *************START************* //  
	

  const struct device * i2c_dev;
   i2c_dev = DEVICE_DT_GET(DT_NODELABEL(i2c2));
  if (i2c_dev == NULL) {
		printk("Unable to bind !\n");
		return;
	 }

	 //************** DEVICE SELECT CODE**************//

	const uint8_t devSelCode[8] = {1, 0, 1, 0, 0, 1, 1, 0};
	 
	int err1 = i2c_write(i2c_dev,devSelCode,8,ST25DV_ADDR_DATA_I2C);
	printk("Device select msg: %d", err1);

     
	 
	
}



prj


CONFIG_STDOUT_CONSOLE=y
CONFIG_PRINTK=y

CONFIG_I2C=y

# CONFIG_LOG=y

Is there possibly something wrong in my configuration that I am not seeing an output in my specified i2c2 pins? Thank you for your help!

RE: Pull down SDA pin i2c

Hkhan7861 — Wed, 09 Nov 2022 08:44:38 GMT

Good day,

I've attempted using these functions and APIs and when I test the board with the multimeter, pin 30 and 31 (my i2c2 pins) get zero voltage output. Do the pins start the output in the prj file or when a write/read sequence is initiated?

Kind regards,

Hassan

RE: Pull down SDA pin i2c

Vidar Berg — Tue, 08 Nov 2022 14:56:21 GMT

Yes, this is our function to start a TWI transfer. However, in general, we recommend to use the Zephyr's driver APIs when possible (https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/hardware/peripherals/i2c.html). You can have a look at the i2c_fujitsu_fram driver sample in the Zephyr tree for an example of how this API can be used.

Kind regards,

Vidar

RE: Pull down SDA pin i2c

Hkhan7861 — Tue, 08 Nov 2022 14:42:36 GMT

Good afternoon

By driver API's, do you mean this function.

struct i2c_msg *DevFnc ;

DevFnc->buf = &devSelCode;

DevFnc->len = 8;

DevFnc->flags = 1;

i2c_nrfx_twim_transfer(i2c_dev,DevFnc,1, 0x53 );

If so, are there any samples where I can see the use of this.

Kind regards,

Hassan

RE: Pull down SDA pin i2c

Vidar Berg — Tue, 08 Nov 2022 09:49:50 GMT

The TWIM peripheral must be configured to transmit data before you can trigger the start task. It is easier to just use the driver APIs to start a transaction as it will take care of the configurations for you.

RE: Pull down SDA pin i2c

Hkhan7861 — Tue, 08 Nov 2022 07:48:18 GMT

Oh I see okay thank you ! so would I just need to use

nrf_twim_task_trigger(p_twim, NRF_TWIM_TASK_STARTTX) and the startup condition will be handled?

Thank you .

RE: Pull down SDA pin i2c

Vidar Berg — Mon, 07 Nov 2022 13:51:04 GMT

[quote userid="120623" url="~/f/nordic-q-a/93581/pull-down-sda-pin-i2c/394403"]I am still not able to find this function. I am not sure you understand my question. Please refer me to where the start condition is handled.[/quote]

There is no function for this because it is handled in HW.

RE: Pull down SDA pin i2c

Hkhan7861 — Mon, 07 Nov 2022 12:21:45 GMT

I will post a picture at a later stage thank you. I am still not able to find this function. I am not sure you understand my question. Please refer me to where the start condition is handled.

RE: Pull down SDA pin i2c

Vidar Berg — Mon, 07 Nov 2022 11:42:57 GMT

The transaction is handled in HW, and not in SW. Please see the "Master write sequence" section of the TWIM chapter for more details on how this works.

[quote userid="120623" url="~/f/nordic-q-a/93581/pull-down-sda-pin-i2c/394382"]Yes, I have used instruments to test and have found that by using an internal pull-up resister, the pin signal level doesnt drop enough.[/quote]

Can you post a picture of this?

RE: Pull down SDA pin i2c

Hkhan7861 — Mon, 07 Nov 2022 11:15:27 GMT

HI, do you mind sending the name or a link to that function so I may see how it works. I can't seem to find it

Yes, I have used instruments to test and have found that by using an internal pull-up resister, the pin signal level doesnt drop enough.

RE: Pull down SDA pin i2c

Vidar Berg — Mon, 07 Nov 2022 11:06:09 GMT

OK, this is the standard way to start a transaction with i2c. Our TWIM peripheral will also create the start condition when you start a new transfer.

Have you tried to probe the SDA and SCL line with a logic analyzer to see what the problem is?

RE: Pull down SDA pin i2c

Hkhan7861 — Mon, 07 Nov 2022 10:50:21 GMT

Hi, thank you for the reply. This is the extent of what the documentation states. Thank you !

6.1.1 Start condition Start is identified by a falling edge of serial data (SDA) while the serial clock (SCL) is stable in the high state. A Start condition must precede any data transfer command. The device continuously monitors (except during a write cycle) the SDA and the SCL for a Start condition, and does not respond unless one is given.

www.st.com/.../st25dv04k.pdf

RE: Pull down SDA pin i2c

Vidar Berg — Mon, 07 Nov 2022 10:39:25 GMT

Hello,

Sorry, I'm not sure if I understand the question correctly. The timing of when the SDA and SCL line are pulled low during transactions is defined by the i2c standard and handled by the HW in our TWIM peripheral (Ref. Two Wire Interface Master (TWIM) timing specifications).

Do you mean that your i2c slave device requires a non-standard wake-up sequence? If so, maybe you could provide me a link to the documentation where this sequence is described?

Best regards,

Vidar