Short initialization example

To simplify the hardware aspect of the WiFi modem we have included a small helper class in the Arduino IDE that is always available to you as a developer. This new class replaces the previous examples on how to do a proper reset and sync.

The first thing you need to do in your sketch is to include the support library by entering:

#include <ChallengerWiFi.h>

After this basically all you need to do before starting the WiFi manager is the following:

if (Challenger2040WiFi.reset())
    Serial.println(F("WiFi Chip reset OK !"));
else
    Serial.println(F("Could not reset WiFi chip !"));

After these step the modem is initialized and is ready to accept your commands. The reset() function of the built in Challenger2040WiFi library will perform a HW reset of the WiFi modem and wait for it to return the “ready” prompt. After this a WiFi manager can be started and start communicating with the modem. Here at iLabs we use the WiFiEspAT library and initializing the stack is as easy as

WiFi.init(ESP_SERIAL_PORT);

At this point you can also do a check to make sure that the data link is setup properly.

if (WiFi.status() == WL_NO_MODULE) {
    Serial.println("Communication with WiFi module failed!");
    // don't continue
    while (true);
}

You are now good to go, so doing something like this:

Serial.println("Waiting for connection to WiFi");
while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.print('.');
}
Serial.println();
Serial.println("Connected to WiFi network.");

will work as expected.

Changing the baudrate

The default baudrate between the RP2040 micro controller and the ESP8285 WiFi modem is 115200 and while this is probably good for most IoT applications that normally don’t send very much data it can sometimes be useful to increase the baudrate. The Challenger2040WiFi contains a method for doing this and again it is super simple to use. Just do the following and the baud rate will be altered on both systems and the devices will be synced up.

Challenger2040WiFi.changeBaudRate(921600);

After this you can proceed to communicate with the device as normal.

Sending and AT command

After the modem has been initialized and it has reported that it is ready you can now send a command to it. Here’s an example on how a simple command can be sent.

Serial2.println("ATE0");

This command simply tells the modem not to repeat everything back that you send to it. If you want to enable this again you would simply send the following command:

Serial2.println("ATE1");

Pass through example

This example Arduino program creates a USB2Serial pass through to the ESP8285. This can be used to flash the ESP with new upgraded software or you can write your own code and use this short snippet to flash the device.

/*
  Challenger USB to serial port.

  This is an example on how to flash the onboard ESP8285.
  TinyUSB must be selected in the Arduino IDE for this sketch to work.

  The ESP8285 should to flashed with the following command:
  esptool.py --port <port> --baud <rate> write_flash -e -fm dout -fs 1MB <filename.bin>

  This program must be compiled with tinyUSB to work.
*/

#include <Arduino.h>

#ifdef USE_TINYUSB
#include <Adafruit_TinyUSB.h>
#define USE_OVERRIDE_LINE_STATE_CB 1
#endif

// Sets the level of debug info that is printed on the serial output
// 0 = No debug information at all
// 1 = Basic debug information
// 2 = Full debug information
#define DEBUG_LVL 0

#define ESP_PORT Serial2
#define PC_PORT Serial
#define DEBUG_PORT Serial1

#define PACKET_SIZE 64

int led = LED_BUILTIN; // the PWM pin the LED is attached to
int led_state = 0;
int wifi_rst = 19;
int wifi_mode = 13;
uint32_t baud_rate = 115200;
static int port = -1;
static int words = 0;
uint8_t ch;
char buffer[PACKET_SIZE];
size_t received;

void tud_cdc_line_coding_cb(uint8_t itf, cdc_line_coding_t const* coding) {
  (void) itf;
#if DEBUG_LVL >= 1
  DEBUG_PORT.printf("n");
#endif 
  if (coding->bit_rate != baud_rate) {
    ESP_PORT.begin(coding->bit_rate);
    baud_rate = coding->bit_rate;
#if DEBUG_LVL >= 1
    DEBUG_PORT.printf("Setting new baudrate to %d ", baud_rate);
#endif 
  }
}

//
// This overrides the stack functionality to capture cdc line state
// changes.
//
#if defined(USE_OVERRIDE_LINE_STATE_CB)
void tud_cdc_line_state_cb(uint8_t itf, bool dtr, bool rts) {
  (void) itf; // interface ID, not used

  if (rts) {
    digitalWrite(wifi_rst, LOW);
#if DEBUG_LVL >= 1
    DEBUG_PORT.printf("RST=low ");
#endif 
  } else {
    digitalWrite(wifi_rst, HIGH);
#if DEBUG_LVL >= 1
    DEBUG_PORT.printf("RST=high ");
#endif 
  }

  if (dtr) {
    digitalWrite(wifi_mode, LOW);
#if DEBUG_LVL >= 1
    DEBUG_PORT.printf("MODE=low");
#endif 
  } else {
    digitalWrite(wifi_mode, HIGH);
#if DEBUG_LVL >= 1
    DEBUG_PORT.printf("MODE=high");
#endif 
  }
#if DEBUG_LVL >= 1
  DEBUG_PORT.printf("n");
#endif

// DTR = false is counted as disconnected
  if (!dtr) {
// touch1200 only with first CDC instance (Serial)
    if (itf == 0) {
      cdc_line_coding_t coding;
      tud_cdc_get_line_coding(&coding);

      if (coding.bit_rate == 1200) {
        TinyUSB_Port_EnterDFU();
      }
    }
  }
}
#endif

// the setup routine runs once when you press reset:
void setup()
{
  pinMode(led, OUTPUT);
  digitalWrite(led, 0);

#if DEBUG_LVL >= 1
  DEBUG_PORT.begin(921600);
  DEBUG_PORT.println("nnnnnnDebug monitor !");
#endif

// Set default baudrates
  ESP_PORT.begin(baud_rate);
  ESP_PORT.setTimeout(10);

  PC_PORT.begin(baud_rate);
  PC_PORT.setTimeout(10);

// Set initial state of control pins
// Normal start when the reset pin is released
  digitalWrite(wifi_rst, LOW);
  pinMode(wifi_rst, OUTPUT);
  digitalWrite(wifi_mode, HIGH);
  pinMode(wifi_mode, OUTPUT);
// delay(1);
// digitalWrite(wifi_rst, HIGH);

  while (!PC_PORT);
  digitalWrite(led, HIGH);
}

//
// The main loop were data is received from the host and then forwarded
// to the ESP8285 and vice versa.
//
void loop() {

  // Handle data from the USB port ment for the ESP8285
  if (PC_PORT.available()) {
    received = PC_PORT.readBytes(buffer, PACKET_SIZE);
    ESP_PORT.write(buffer, received);

#if DEBUG_LVL >= 2
    if (port != 1) {
      port = 1;
      words = 0;
      DEBUG_PORT.println("nFrom USB to ESP8285 ==================================");
    }
    for (int i=0;i<received;i++) {
      DEBUG_PORT.printf("%02x ", buffer[i]);
      if (++words > 15) {
        words = 0;
        DEBUG_PORT.println();
      }
    }
#endif
  }

  // Handle response data from the ESP8285
  if (ESP_PORT.available()) {
    received = ESP_PORT.readBytes(buffer, PACKET_SIZE);
    PC_PORT.write(buffer, received);

#if DEBUG_LVL >= 2
    if (port != 2) {
      port = 2;
      words = 0;
      DEBUG_PORT.println("nFrom ESP8285 to USB ==================================");
    }
    for (int i=0;i<received;i++) {
      DEBUG_PORT.printf("%02x ", buffer[i]);
      if (++words > 15) {
        words = 0;
        DEBUG_PORT.println();
      }
    }
#endif
  }
}