examples/rf24_ATTiny/timingSearch3pin/timingSearch3pin.ino

2014 Contribution by tong67
Updated 2020 by 2bndy5 for the SpenceKonde ATTinyCore
The RF24 library uses the ATTinyCore by SpenceKonde

This sketch can be used to determine the best settle time values to use for RF24::csDelay in RF24::csn() (private function).

See also

RF24::csDelay

The settle time values used here are 100/20. However, these values depend on the actual used RC combination and voltage drop by LED. The intermediate results are written to TX (PB3, pin 2 – using Serial).

For schematic details, see introductory comment block in the rf24ping85.ino sketch.

 
/*
 * This sketch can determine the best settle time values to use for
 * macros, defined as RF24_CSN_SETTLE_HIGH_DELAY and RF24_CSN_SETTLE_LOW_DELAY,
 * in RF24::csn().
 * The settle time values used here are 100/20. However, these values depend
 * on the actual used RC combiniation and voltage drop by LED. The
 * intermediate results are written to TX (PB3, pin 2 -- using Serial).
 *
 * For schematic details, see introductory comment block in the
 * examples/rf24_ATTiny/rf24ping85/rf24ping85.ino sketch.
 */
 
#include <stdio.h>
#include <SPI.h>
#include <Arduino.h>
#include <nRF24L01.h>
 
 
#if defined(ARDUINO) && !defined(__arm__)
#if defined(__AVR_ATtinyX5__) || defined(__AVR_ATtinyX4__)
#define RF24_TINY
#endif
#endif
 
/****************************************************************************/
 
#if defined(RF24_TINY)
 
// when Attiny84 or Attiny85 is detected
#define CE_PIN 3  
#define CSN_PIN 3 
#else
// when not running on an ATTiny84 or ATTiny85
#define CE_PIN 7  
#define CSN_PIN 8 
#endif
 
#define MAX_HIGH 100
#define MAX_LOW 100
#define MINIMAL 8
 
// Use these adjustable variables to test for best configuration to be used on
// the ATTiny chips. These variables are defined as macros in the library's
// RF24/utility/ATTiny/RF24_arch_config.h file. To change them, simply define
// the corresponding macro(s) before #include <RF24> in your sketch.
uint8_t csnHighSettle = MAX_HIGH;  // defined as RF24_CSN_SETTLE_HIGH_DELAY
uint8_t csnLowSettle = MAX_LOW;    // defined as RF24_CSN_SETTLE_LOW_DELAY
 
/****************************************************************************/
void ce(bool level) {
  if (CE_PIN != CSN_PIN) digitalWrite(CE_PIN, level);
}
 
/****************************************************************************/
void csn(bool mode) {
  if (CE_PIN != CSN_PIN) {
    digitalWrite(CSN_PIN, mode);
  } else {
    // digitalWrite(SCK, mode);
    if (mode == HIGH) {
      PORTB |= (1 << PINB2);             // SCK->CSN HIGH
      delayMicroseconds(csnHighSettle);  // allow csn to settle
    } else {
      PORTB &= ~(1 << PINB2);           // SCK->CSN LOW
      delayMicroseconds(csnLowSettle);  // allow csn to settle
    }
  }
}
 
/****************************************************************************/
uint8_t read_register(uint8_t reg) {
  csn(LOW);
  SPI.transfer(R_REGISTER | reg);
  uint8_t result = SPI.transfer(0xff);
  csn(HIGH);
  return result;
}
 
/****************************************************************************/
void write_register(uint8_t reg, uint8_t value) {
  csn(LOW);
  SPI.transfer(W_REGISTER | reg);
  SPI.transfer(value);
  csn(HIGH);
}
 
/****************************************************************************/
void setup(void) {
 
#ifndef __AVR_ATtinyX313__
  // not enough memory on ATTiny4313 or ATTint2313(a) to use Serial I/O for this sketch
 
  // start serial port and SPI
  Serial.begin(115200);
  SPI.begin();
  // configure CE and CSN as output when used
  pinMode(CE_PIN, OUTPUT);
  if (CSN_PIN != CE_PIN)
    pinMode(CSN_PIN, OUTPUT);
 
  // csn is used in SPI transfers. Set to LOW at start and HIGH after transfer. Set to HIGH to reflect no transfer active
  // SPI command are accepted in Power Down state.
  // CE pin represent PRX (LOW) or PTX (HIGH) mode apart from register settings. Start in PRX mode.
  ce(LOW);
  csn(HIGH);
 
  // nRF24L01 goes from to Power Down state 100ms after Power on Reset ( Vdd > 1.9V) or when PWR_UP is 0 in config register
  // Goto Power Down state (Powerup or force) and set in transmit mode
  write_register(NRF_CONFIG, read_register(NRF_CONFIG) & ~_BV(PWR_UP) & ~_BV(PRIM_RX));
  delay(100);
 
  // Goto Standby-I
  // Technically we require 4.5ms Tpd2stby+ 14us as a worst case. We'll just call it 5ms for good measure.
  // WARNING: Delay is based on P-variant whereby non-P *may* require different timing.
  write_register(NRF_CONFIG, read_register(NRF_CONFIG) | _BV(PWR_UP));
  delay(5);
 
  // Goto Standby-II
  ce(HIGH);
  Serial.print("Scanning for optimal setting time for csn");
 
 
  /************************** Main program *********************************/
 
  uint8_t result;  // used to compare read/write results with read/write cmds
  bool success = true;
  uint8_t bottom_success;
  bool bottom_found;
  uint8_t value[] = { 5, 10 };
  uint8_t limit[] = { MAX_HIGH, MAX_LOW };
  uint8_t advice[] = { MAX_HIGH, MAX_LOW };
 
  // check max values give correct behavior
  for (uint8_t k = 0; k < 2; k++) {
    bottom_found = false;
    bottom_success = 0;
    while (bottom_success < 255) {
      csnHighSettle = limit[0];
      csnLowSettle = limit[1];
      // check current values
      uint8_t i = 0;
      while (i < 255 && success) {
        for (uint8_t j = 0; j < 2; j++) {
          write_register(EN_AA, value[j]);
          result = read_register(EN_AA);
          if (value[j] != result) {
            success = false;
          }
        }
        i++;
      }
      // process result of current values
      if (!success) {
        Serial.print("Settle Not OK. csnHigh=");
        Serial.print(limit[0], DEC);
        Serial.print(" csnLow=");
        Serial.println(limit[1], DEC);
        limit[k]++;
        bottom_found = true;
        bottom_success = 0;
        success = true;
      } else {
        Serial.print("Settle OK. csnHigh=");
        Serial.print(limit[0], DEC);
        Serial.print(" csnLow=");
        Serial.println(limit[1], DEC);
        if (!bottom_found) {
          limit[k]--;
          if (limit[k] == MINIMAL) {
            bottom_found = true;
            bottom_success = 0;
            success = true;
          }
        } else {
          bottom_success++;
        }
      }
    }  // while (bottom_success < 255)
    Serial.print("Settle value found for ");
    if (k == 0) {
      Serial.print("csnHigh: ");
    } else {
      Serial.print("csnLow: ");
    }
    Serial.println(limit[k], DEC);
    advice[k] = limit[k] + (limit[k] / 10);
    limit[k] = 100;
  }  // for (uint8_t k = 0; k < 2; k++)
  Serial.print("Advised Settle times are: csnHigh=");
  Serial.print(advice[0], DEC);
  Serial.print(" csnLow=");
  Serial.println(advice[1], DEC);
 
#endif  // not defined __AVR_ATtinyX313__
}
 
 
void loop(void) {}  // this program runs only once, thus it resides in setup()