Using shiftout or SPI.Transfert

Projects Networking, Protocols, and Devices
1

Hello everybody,

I wanna use a board from rfcandy,
with the chip LMX2322, this chip is a PLL and need two register to be programmed, R and N.

I'have generate the value for 868Mhz frequency test, with the software from the same author

R-reg N-reg 001151 010F40

Registers are 18bits, since Arduino can only send 8bits each time, i use shiftOut function,
how can i split register to send correct value ?

shiftout can send bits per bits or i need to create something like that ?
SHIFTOUT (dataPin, clockPin, MSBFIRST, 8bits);
SHIFTOUT (dataPin, clockPin, MSBFIRST, 8bits);
SHIFTOUT (dataPin, clockPin, MSBFIRST, 8bits);

/*
Xtal = 16,8Mhz    
Freq = 868Mhz      
R-Counter  Ref frequency N-Counter    Error   R-reg        N-reg
168          100000 Hz      8680           0 Hz    001151     010F40
*/

const char RegR = 0x01151;
const char RegN = 0x10F40;

int clockPin = 13; //Clk
int dataPin = 11; //Data
int latchPin = 10; //Enb

void setup()
{
 pinMode(clockPin, OUTPUT);
 pinMode(dataPin, OUTPUT);
 pinMode(latchPin, OUTPUT);
}

void loop() 
{
    digitalWrite(latchPin, LOW);
    
    byte byte1 = (RegN >> 8);
    shiftOut(dataPin, clockPin, MSBFIRST, byte1);
    shiftOut(dataPin, clockPin, MSBFIRST, RegN);

    byte byte2 = (RegR >> 8);
    shiftOut(dataPin, clockPin, MSBFIRST, byte2);
    shiftOut(dataPin, clockPin, MSBFIRST, RegR); 
    
    digitalWrite(latchPin, HIGH);
    delay(500);
}

(I have use VCO testing software, and PIC from based design, and its work fine, so its not a hardware problem)

also, i have removed following lines, because it's stuck arduino, i have checked clck and data pin via scope

#include <SPI.h>
SPI.begin();
SPI.setBitOrder(MSBFIRST);
SPI.setDataMode(SPI_MODE0); // National Semiconductor use MICROWIRE => CPOL = 0 & CPHA = 0
SPI.setClockDivider(SPI_CLOCK_DIV4);

anybody can help me ?

regards

2

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3

The challenge I see with this IC is the SPI transfer is 18 bits. The normal SPI functions, including shiftOut, send in 8 bit increments, so your choices are 16 bits or 24 bits.

You might get away with bit banging the SPI. Nick Gammon is the person who would know how to do this.