Delay to generate I2C ACK by LPC804

[Bhavin_Dhulkotiya]

Hi,

We are using LPC804 I2C slave with interrupt mode. As shown in attached image we are getting ~20 micro second delay before ACK generation. So after debugging we found that software takes this time to handle I2C interrupt. However, we haven't add any extra code in provided SDK example. The same delay appears when doing transfers at both 100kb/s and 400kb/s. Could you suggest any way to reduce it or to handle I2C ACK by hardware?

LPC804_I2C_22us_ACK_Delay.PNG

[DanielRuvalcaba]

Hello

Could you please tell me what device are you using as Master?

Have you tried the LPC804 as Master? And if not, could you please try this configuration and see if this problem still occurs?

Regards, Daniel.

[Bhavin_Dhulkotiya]

@DanielRuvalcaba 

We are using the Aardvark as a master. As the issue is on slave we haven't tried LPC804 as master. Although we have used different masters with LPC804, the issue persists.

[DanielRuvalcaba]

Hi,

Could you please verify that your slave is not having problems with something related to clock stretching?

Also, could you please try your application with another slave to see if the problem still going?                                         

Another thing you can try is to optimize the ISR code.

I drop you some links that might be helpful:

https://community.nxp.com/t5/Kinetis-Microcontrollers/I2C-Clock-Stretching-on-MK10DX64VFM5/m-p/24655...

https://community.nxp.com/t5/Kinetis-Microcontrollers/how-to-reduce-the-delay-of-i2c/m-p/372178

https://community.nxp.com/t5/Kinetis-Microcontrollers/I2C-Delay-between-ACK-and-Data-from-slave/m-p/...

Best regards, Daniel.