Minimum time possible to send 32byte data with NRF24L01 module ?

RE: Minimum time possible to send 32byte data with NRF24L01 module ?

Kenneth — Wed, 29 Sep 2021 19:38:18 GMT

The only factor you can adjust here is the SPI, so that is where you need to look at, for instance timing between IRQ, CSN and SPI.

Best regards,

Kenneth

RE: Minimum time possible to send 32byte data with NRF24L01 module ?

sukru — Wed, 29 Sep 2021 13:15:44 GMT

What should be done to make SPI faster? I use 10MHZ SPI frequency which is the maximum frequency that NRF24L01 accept. My MCU is PIC18F24K42.

And Do I have to wait for the TX_DS bit to be 1 to send data again ? Do I have to wait for the time on air to send new data?

As you calculate the dead time, for about 100us left to reach maximum 400us aim. If we use the maximum SPI frequency that NRF24L01 accept(10MHZ) our SPI speed should be 0.8us/per bytes let me say that as 1us including dead times between bytes. Totally we spend 38*1us + 4us(flush)+4us(reset status) = 46us for SPI. But in reality SPI spend more time than that.

RE: Minimum time possible to send 32byte data with NRF24L01 module ?

Kenneth — Wed, 29 Sep 2021 11:38:50 GMT

I recommend to get an oscilloscope or logic analyzer so you may measure SPI, CE, and VDD_PA pins. The VDD_PA pin should go high 150us after CE is pulled high, and VDD_PA will stay high during transmission. Typically transmitting 32byte data with 4byte address + 2byte crc @ 2Mbps will take: ((32+4+2)bytes*8bit/byte)/2Mbps= 152us. It's not possible to reduce 150us + 152us, so you will need to look into how to improve the SPI transfer.

Kenneth