I2C in QuecOpen for EC21

Technical Subjects Open Solution
1

Hi,

I would like to use I2C to read an external accelerometer. I’m using QuecOpen on EC21:

Quectel
EC21
Revision: EC21EFAR06A05M4G

SDK is: EC21EFAR06A05M4G_OCPU_20.001.20.001_SDK

I tried I2C example in ql-ext-sdk/example folder but if I check I2C_SCL and I2C_SDA using an oscilloscope but no signal is detected (note I added 4.7kohm resistor as pull-up to Vdd-ext).

Is I2C available for “generic purpose” or is it related only for CODEC interface?
Is it possible to remap it in the kernel?

Thanks for support!

2

Hi
The I2C interface can be used as a general interface. Check the software to ensure that the configuration is correct and can be used for external sensors.

3

Dear @Jouni.yang-Q,

I’m testing I2C using “example_i2c.c” reported in SDK example folder.

#include "ql_oe.h"


#define I2C_DEV         "/dev/i2c-2"	//i2c-2 on EC20xx, i2c-4 on AG35
#define I2C_SLAVE_ADDR  0x18	//codec 3104
#define WHO_AM_I        0x02
#define WHO_AM_I_VALUE  0x12


int main(int argc, char* argv[])  
{
    int iRet;

    /*
     * Open I2C device with read-write mode,
     * and write slave address.
     */
    int fd_i2c = Ql_I2C_Init(I2C_DEV);
    printf("< Ql_I2C_Init=%d >\n", fd_i2c);
    if (fd_i2c < 0)  
    {
        printf("< Fail to open i2c >\n");
        return -1;  
    }  

    /*
     * Write "who am i".
     */
    unsigned char wrtBuff[2] = {WHO_AM_I_VALUE, 0};
    iRet = Ql_I2C_Write(fd_i2c, I2C_SLAVE_ADDR, WHO_AM_I, wrtBuff, 1);
    printf("< write i2c value=0x%x, iRet=%d >\n", WHO_AM_I_VALUE, iRet);

    /*
     * Read the response for "who am i".
     */
    unsigned char rdBuff[2] = {0, 0};
    iRet = Ql_I2C_Read(fd_i2c, I2C_SLAVE_ADDR, WHO_AM_I, rdBuff, 1);
    printf("< read i2c iRet=%d, value=0x%x%x >\n", iRet, rdBuff[1], rdBuff[0]);//Little endian

    Ql_I2C_Deinit(fd_i2c);

Is “/dev/i2c-2” the correct one to use? I don’t see any CLK signal on oscilloscope on SCL pin. I expected to find some train of bits on oscilloscope.

Do you have another example I can test?

Thank you and regards.

4

Hello @Jouni.yang-Q,
Do you have any chance to send me a working example of I2C with EC21E and QuecOpen so I can test on my side?
Otherwise I have to think about to write i2c in bit-banging (which I would avoid…)

Thank you and regards

5

Hello @davdav,
did you solved?

Have a good day