timer1-4 Inaccurate timing issue on nrf5-softdevice

RE: timer1-4 Inaccurate timing issue on nrf5-softdevice

david@2024 — Wed, 18 Dec 2024 07:15:56 GMT

thank you very much。I'll refer to it

RE: timer1-4 Inaccurate timing issue on nrf5-softdevice

Vidar Berg — Wed, 18 Dec 2024 07:09:07 GMT

Thanks for confirming. If the channel selection command can be made the same length as the start sampling command, you might be able to use the EasyDMA array list feature to perform the entire SPI transaction sequence without CPU involvement.

RE: timer1-4 Inaccurate timing issue on nrf5-softdevice

david@2024 — Wed, 18 Dec 2024 07:04:59 GMT

1.Is the ADC channel input changed by sending a SPI command or by using a GPIO output?

the ADC channel input changed by sending a SPI command.

RE: timer1-4 Inaccurate timing issue on nrf5-softdevice

Vidar Berg — Wed, 18 Dec 2024 07:01:15 GMT

Hi,

Is the ADC channel input changed by sending a SPI command or by using a GPIO output?

RE: timer1-4 Inaccurate timing issue on nrf5-softdevice

david@2024 — Wed, 18 Dec 2024 01:39:54 GMT

Hi,

thanks.

1.Is it a requirement to sample the ADC while connected with BLE?

yes.sample the ADC while connected with BLE

2.it seems you need to change the ADC input channel between each sample.

yes.it need to change ADC input channel,that need to cpu involvement.so I think,in my case, it need TIMER event to change ADC input channel,and start sample the ADC.

RE: timer1-4 Inaccurate timing issue on nrf5-softdevice

Vidar Berg — Mon, 16 Dec 2024 13:56:30 GMT

Hi,

The "Repeated transfers" section of the driver documentation here: https://docs.nordicsemi.com/bundle/sdk_nrf5_v17.1.0/page/hardware_driver_spi_master.html explains how you can set up PPI-triggered SPI transfers which can help you repeat the same SPI transfers over and over again without CPU involvement. Unfortunately, I'm not sure this will work in your case, as it seems you need to change the ADC input channel between each sample.

Is it a requirement to sample the ADC while connected with BLE?

RE: timer1-4 Inaccurate timing issue on nrf5-softdevice

david@2024 — Fri, 13 Dec 2024 06:24:24 GMT

Hi，

1. I recommend you use PPI to connect the TIMER event

How to use PPI to The following application scenarios?

(1)The application scenarios ：

（2）code

thanks!

RE: timer1-4 Inaccurate timing issue on nrf5-softdevice

Vidar Berg — Thu, 12 Dec 2024 10:32:34 GMT

Hi,

The Low-frequency (LF) clock is the 32KHz clock source. But the TIMERs run off the high frequency clock source.

https://docs.nordicsemi.com/bundle/ps_nrf52832/page/clock.html

RE: timer1-4 Inaccurate timing issue on nrf5-softdevice

david@2024 — Thu, 12 Dec 2024 10:22:06 GMT

Hi，Thank you for your reply.

NRF_SDH_CLOCK_LF_SRC=NRF_CLOCK_LF_SRC_SYNTH and sd_clock_hfclk_request() ，what's the different？

RE: timer1-4 Inaccurate timing issue on nrf5-softdevice

Vidar Berg — Wed, 11 Dec 2024 08:23:55 GMT

Hello,

Interrupts used by the Softdevice can preempt or block your application interrupts for shorter durations which can lead to jitter, please refer to the Processor usage patterns and availability section of the softdevice specification for more details. If you only need to toggle an GPIO on this timer event, I recommend you use PPI to connect the TIMER event directly to a GPIOTE task as demonstrated by the peripheral GPIOTE example. This will let you toggle the gpio without any CPU involvement.

Best regards,

Vidar

Edit: to further increase the accuracy, you can request the HF crystal oscillator by calling this function after you've enabled the Softdevice: sd_clock_hfclk_request()