WRITE/READ COMMAND FOR NRF24L01 VIA SPI

[paolo lucantonio]

Hi, i'm using the nrf24l01 with a zynq board to use it as radiocontrol; i'm trying to configure the nrf as receiver so that i'm able to send data from another nrf connected to an arduino. The first step i had to do, as i understood frome the datasheet, is being able to write and read register from nrf, so that i can configure nrf as receiver and also i can modify parameters for the communication (as bit rate, frequency,ecc). i tried to write the CF_REG with 00000011 (that are the setting for PRIM_RX and PWR_UP) using spi, and then reading the new content of the register. As i discovered i had to send the command and then the data i must overwrite, so i first sent 00100000 (that should be write register CF_REG), and then i sent 00000011, but it seems not to work. The first question i'd like to ask is if i have to send the 2 bytes with two different commands or if i can send a single command with a 2 bytes data (00100000-00000011 in this case).
The second question is if anyone already worked with zynq and is able to determine if i'm configuring properly the sdk. the code i wrote is below, thanks

void write(XSpiPs *myinstanceptr){
u8 * commandptr;
u16 command = 0b0010001000000011;
commandptr = &command;
u8 * dataptr;
u8 data = 0b00000011;
dataptr = &data;
XSpiPs_SetSlaveSelect(myinstanceptr,0);
(myinstanceptr)->IsBusy=0x00000000;
XSpiPs_Transfer(myinstanceptr,commandptr,NULL,2);
(myinstanceptr)->IsBusy=0x00000000;
//XSpiPs_Transfer(myinstanceptr,dataptr,NULL,1);
//(myinstanceptr)->IsBusy=0x00000000;
XSpiPs_SetSlaveSelect(myinstanceptr,0X0F);

}


u8 read(XSpiPs *myinstanceptr){
u8 * commandptr;
u8 command = 0x00;
commandptr = &command;
u8 * dataptr;
u8 data;
u8 *rcvptr2;
u8 rcv2;
rcvptr2 = &rcv2;
dataptr = &data;
u8 * rcvptr;
u8 rcv;
rcvptr = &rcv;
XSpiPs_SetSlaveSelect(myinstanceptr,0);
(myinstanceptr)->IsBusy=0x00000000;
XSpiPs_Transfer(myinstanceptr,commandptr,rcvptr2,1);
(myinstanceptr)->IsBusy=0x00000000;
XSpiPs_Transfer(myinstanceptr,dataptr,rcvptr,1);
(myinstanceptr)->IsBusy=0x00000000;
XSpiPs_SetSlaveSelect(myinstanceptr,0x0F);
return rcv;
}

int main(){
init_platform();
Xil_Out8(IRQ_BASE_ADDR,0x01);
XSpiPs *myinstanceptr;
XSpiPs_Config *myinstanceptr2;
XSpiPs instanceptr;
XSpiPs_Config instanceptr2;
myinstanceptr = &instanceptr;
myinstanceptr2 = &instanceptr2;
myinstanceptr2->InputClockHz = XPAR_PS7_SPI_0_SPI_CLK_FREQ_HZ;
XSpiPs_CfgInitialize(myinstanceptr,myinstanceptr2,XPAR_PS7_SPI_0_BASEADDR);
XSpiPs_SetOptions(myinstanceptr,XSPIPS_MASTER_OPTION);
//XSpiPs_SetClkPrescaler(myinstanceptr,XSPIPS_CLK_PRESCALE_256);
u8 result;
result = XSpiPs_IsManualChipSelect(myinstanceptr);
result = XSpiPs_IsDecodeSSelect(myinstanceptr);
result = XSpiPs_IsManualStart(myinstanceptr);
u8 *txbuf;
u8 *rxbuf;
u16 tx = 0b11001111;
u8 rx;
txbuf = &tx;
rxbuf = ℞
while(1){
write(myinstanceptr);
result = read(myinstanceptr);

}


return 0;

}

[awneil]

These chips are very widely used - so there  are a lot of examples & tutorials out there.

For example:

https://www.avrfreaks.net/comment/2758091#comment-2758091

Also beware that there are fakes out there:

https://www.avrfreaks.net/comment/2764341#comment-2764341

[paolo lucantonio]

i checked many codes, i also studied all the arduino library for NRF and for what i understood the functions for writing and reading register on NRF should be correct but they don't work so it seems i'm missing something that i can't get

[awneil]

Probably easier to stick to your other thread:

https://devzone.nordicsemi.com/f/nordic-q-a/52088/write-read-command-for-nrf24l01-via-spi

As Kenneth said there, you need a logic analyser to see what's happening...

[paolo lucantonio]

hi everyone, i was able to use a logic analyser and solve the problem, but now another one appeared: i'm trying to configure the nrf to rx and according to the state diagram i realized that: as the nrf is supplied and the voltage goes over 1,9V the nrf goes in the power down mode. i should be able to send via spi the command to set the pwr_up bit to 1 to allow the nrf to go the stand_by 1 state and after the 1,5ms needed to the nrf i should  set both ce and prim_rx to 1, am i wrong? The main problem is that the nrf is ignoring the writing command; are needed other instrunction? (i also tried to first read the config_Register and then to put it in a bit-a-bit or to my data byte and then sending the resulting byte to nrf but with 0 result. p.s the reading command isn't having any problem )

[awneil]

paolo lucantonio said:

i was able to use a logic analyser and solve the problem

So, for the benefit of others who may have similar issues, what was the problem?

And how was it solved?

Probably better to put that in the other thread ...

paolo lucantonio said:

now another one appeared

Please keep to one problem per thread.

[paolo lucantonio]

The problem was that the ZYNQ board had as default configuration the deassertion of the CSN between the end of a word and the beginning of the following one so that every byte sent to nrf were considered as a new command for nrf and it sent to the miso signal the status register every time. Luckily this option could be removed and now the csn is kept asserted. (i'm sorry for the double problem now i'll close this one and i'll open a new thread, thank you)