twi interrupt delay in nrf51822

[NIDHIN K]

I'm using nrf51822 , softdevice S110 and the SDK10 . Im reading data from the sensor mpu9250 using i2c at 400Khz( Maximum) frequency. It taking more delay than expected to read data from register.  I have attached an image of output wave form of i2c data read using logic analyzer .

 i have to read 6 bytes from mpu register , so first i write reading register  then wait for interrupt ( wait for NRF_DRV_TWI_TX_DONE )  and then read 6bytes data from mpu and wait for interrupt NRF_DRV_TWI_RX_DONE . But the interrupt delay is taking 80 -90 us. That you can see in image1 and its also taking 17us delay between each data read, check image2.

1. Why is taking these delay ???

2. Is it possible to reduce this delay ??

[Kenneth]

For new development I suggest to check out the nRF52832 (or other variants of the nRF52-series), since they can support EasyDMA for serial transactions without delay between bytes. On the nRF51-series there will be an interrupt delay, and the delay also depends on whether the softdevice is enabled or not.

Best regards,
Kenneth