Kinetis Microcontrollers中的主题 Re: KL25z I2C two bytes reading

KL25z I2C two bytes reading

asdasdaram — Sat, 25 Jan 2014 01:54:41 GMT

Hello, how would a baremetal code of reading two bytes with I2c from a sensor look like.

The following code ist from twr-kl25Demo and reads one byte. How i could read the 2. byte. The Sensor just excect an Acknowledge after the first byte, but how to integrade that in the code below. I Also dont understand why theres

i2c_give_nack(I2C0_B); after

i2c_get_ack(I2C0_B);

i2c_set_rx_mode(I2C0_B);

and why there is a reading after i2c_stop. Could someone Comment this pls. Thanks a lot

uint8 result;

i2c_start(I2C0_B);

i2c_write_byte(I2C0_B, MMA8451_I2C_ADDRESS | I2C_WRITE);

i2c_wait(I2C0_B);

i2c_get_ack(I2C0_B);

i2c_write_byte(I2C0_B, addr);

i2c_wait(I2C0_B);

i2c_get_ack(I2C0_B);

i2c_repeated_start(I2C0_B);

i2c_write_byte(I2C0_B, MMA8451_I2C_ADDRESS | I2C_READ);

i2c_wait(I2C0_B);

i2c_get_ack(I2C0_B);

i2c_set_rx_mode(I2C0_B);

i2c_give_nack(I2C0_B);

result = i2c_read_byte(I2C0_B);

i2c_wait(I2C0_B);

i2c_stop(I2C0_B);

result = i2c_read_byte(I2C0_B);

pause();

return result;

Re: KL25z I2C two bytes reading

Robin_Shen — Sun, 26 Jan 2014 01:10:34 GMT

Hi asdasd aram

I think you can refer the Typical I2C interrupt routine in KL25P80M48SF0RM.pdf

See below:

Hope that help.

Best Regards

Robin

Re: KL25z I2C two bytes reading

asdasdaram — Sun, 26 Jan 2014 03:08:18 GMT

Thanks for that, but it did not help, i need to understand the code. The routine in the figure is clear, but how to programm, thats the real challenge. Its unclear where to set and unset acknowledge and where to read the two bytes, both after i2c_stop(I2C0_B)?. It would help a lot if someone could explain the code and set it to read two bytes.

Thanks a lot

Best Regards

Re: KL25z I2C two bytes reading

kerryzhou — Mon, 27 Jan 2014 05:19:11 GMT

Hi asdasd aram,

Please see my reply in your another tip:https://community.freescale.com/thread/318549

I wish it useful to you!

If you still have question, please let me know!

Best regards!

Jing