Embedded

ESPAsyncWebServer JSON response example for ArduinoJson 6

The ESPAsyncWebserver page features an example for generating a basic JSON response using ArduinoJson:

#include "AsyncJson.h"
#include "ArduinoJson.h"

AsyncResponseStream *response = request->beginResponseStream("application/json");
DynamicJsonBuffer jsonBuffer;
JsonObject &root = jsonBuffer.createObject();
root["heap"] = ESP.getFreeHeap();
root["ssid"] = WiFi.SSID();
root.printTo(*response);
request->send(response);

However, that example is made for ArduinoJson 5.x whereas most users want to use the updated ArduinoJson 6.x.

ArduinoJson 6.x minimal ESPAsyncWebserver example:

AsyncResponseStream *response = request->beginResponseStream("application/json");
DynamicJsonDocument json(1024);
json["status"] = "ok";
json["ssid"] = WiFi.SSID();
json["ip"] = WiFi.localIP();
serializeJson(json, *response);
request->send(response);

 

Posted by Uli Köhler in Embedded, ESP8266/ESP32, PlatformIO

How to fix ArduinoJson error: DynamicJsonBuffer is a class from ArduinoJson 5

When you see an error message like

Compiling .pio\build\d1_mini\src\main.cpp.o
src\main.cpp:22:11: error: DynamicJsonBuffer is a class from ArduinoJson 5. Please see arduinojson.org/upgrade to learn how to upgrade your program to ArduinoJson version 6
       DynamicJsonBuffer jsonBuffer;

in your PlatformIO or Arduino project using the ArduinoJson library, your code was written for an old version of ArduinoJson.

According to the official ArduinoJson 5 to ArduinoJson 6 migration guide, you need to use DynamicJsonDocument instead. Note that DynamicJsonDocument uses a slightly different API compared to DynamicJsonDocument, hence you might need to adjust more than just changing the class names. But as a first step, replace e.g.

DynamicJsonBuffer json;

by

DynamicJsonDocument json(1024);
Posted by Uli Köhler in Arduino, ESP8266/ESP32, PlatformIO

How to fix ArduinoJson error: ‘ArduinoJson::JsonObject’ has no member named ‘printTo’

Problem:

While trying to build your project using ArduinoJson, you see an error message like

src\main.cpp:26:12: error: 'ArduinoJson::JsonObject' has no member named 'printTo'
       root.printTo(*response);

Solution:

The code you’re using is for an older version of ArduinoJson: It was written for ArduinoJson version 5.x while you’re using ArduinoJson version 6.x. Use serializeJson() instead of  root.printTo(*response):

serializeJson(root, *response);

See the official ArduinoJson guide for Migrating from version 5 to 6 for further information on which calls you need to replace.

 

Posted by Uli Köhler in Arduino, Embedded, ESP8266/ESP32, PlatformIO

How to print ESP8266 Wifi IP address

// Print wifi IP addess
Serial.println("IP address: ");
Serial.println(WiFi.localIP());

Documentation for Wifi.localIP()

Posted by Uli Köhler in ESP8266/ESP32

ESP8266 WPA EAP minimal example

This example shows how to connect to WPA2-EAP wifi with username and password on the ESP8266 using the Arduino framework:

#include <Arduino.h>
#include <ESP8266WiFi.h>
#include "wpa2_enterprise.h"

char ssid[] = "MyWifiSSID";
char username[] = "MyEAPUsername";
char password[] = "MyEAPPassword";

void setup()
{
  Serial.begin(115200);

  wifi_set_opmode(STATION_MODE);

  // Configure SSID
  struct station_config wifi_config;

  memset(&wifi_config, 0, sizeof(wifi_config));
  strcpy((char *)wifi_config.ssid, ssid);

  wifi_station_set_config(&wifi_config);

  // DO NOT use authentication using certificates
  wifi_station_clear_cert_key();
  wifi_station_clear_enterprise_ca_cert();

  // Authenticate using username/password
  wifi_station_set_wpa2_enterprise_auth(1);
  wifi_station_set_enterprise_identity((uint8 *)username, strlen(username));
  wifi_station_set_enterprise_username((uint8 *)username, strlen(username));
  wifi_station_set_enterprise_password((uint8 *)password, strlen(password));

  // Connect
  wifi_station_connect();

  // Wait for connect
  while (WiFi.status() != WL_CONNECTED)
  {
    Serial.println("Wifi connecting...");
    delay(500);
  }
  // Print wifi IP addess
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
}

void loop()
{
  // put your main code here, to run repeatedly:
}

 

Posted by Uli Köhler in ESP8266/ESP32

Minimal ESP8266 WiFi example

#include <Arduino.h>
#include <ESP8266WiFi.h>

void setup() {
  Serial.begin(115200);
  WiFi.begin("MySSID", "MyPassword");
  while (WiFi.status() != WL_CONNECTED) {
    Serial.println("Wifi connecting...");
    delay(500);
  }
  Serial.println("Wifi connected");
}

void loop() {
  // put your main code here, to run repeatedly:
}

 

Posted by Uli Köhler in C/C++, ESP8266/ESP32

How to add GitHub repository to PlatformIO platformio.ini lib_deps

You can directly add a GitHub repository as a PlatformIO library dependency by specifying its repository URL in lib_deps in platformio.ini

lib_deps =
    https://github.com/Bodmer/U8g2_for_TFT_eSPI

Note that the GitHub repository must be a valid PlatformIO library i.e. it must have library.json or library.properties in its root directory. https://github.com/Bodmer/U8g2_for_TFT_eSPI is an example for a library that can be included into PlatformIO.

Posted by Uli Köhler in PlatformIO

How to fix PlatformIO ESP8266/ESP32 fatal error: SPI.h: No such file or directory

Problem:

You are trying to compile your PlatformIO application for the ESP8266 or ESP32 but you’re seeing an error message like

In file included from .pio/libdeps/d1_mini/TFT_eSPI/TFT_eSPI.cpp:17:0:
.pio/libdeps/d1_mini/TFT_eSPI/TFT_eSPI.h:32:17: fatal error: SPI.h: No such file or directory

*************************************************************
* Looking for SPI.h dependency? Check our library registry!
*
* CLI  > platformio lib search "header:SPI.h"
* Web  > https://platformio.org/lib/search?query=header:SPI.h
*
*************************************************************

 #include <SPI.h>

This problem is common using the TFT_eSPI library.

Solution:

First, ensure that your platformio.ini has

framework = arduino

If you’re using a different frameworkSPI.h won’t be available since it’s a part of the Arduino framework !

Secondly, add this line to your platformio.ini:

lib_ldf_mode = deep+

and recompile your source code. This will reconfigure the library dependency finder (ldf) to find dependencies of dependency libraries:

Dependency Graph
|-- <TFT_eSPI> 2.3.52
|   |-- <SPI> 1.0

 

Posted by Uli Köhler in ESP8266/ESP32, PlatformIO

Where to find info about mbed mbed_app.json overridable parameters?

The first resource can have a look at is the platform configuration option page. Additionally, check the manual on how to use the mbed CLI to show configuration options.

Additionally, you can look at targets.json on GitHub:

For example, "Target" => "config" => "default-adc-vref" would need to be entered like this into mbed_app.json:

{
    "target_overrides": {
      "*": {
          "target.default-adc-vref": 3300
      }
    }
}

 

Posted by Uli Köhler in C/C++, mbed, PlatformIO

How to fix mbed AnalogIn.read_voltage() returning nan or 0.000 (PlatformIO)

Problem:

You are trying to read an ADC voltage in mbed / PlatformIO like this:

AnalogIn myADC(PA_5); 
// Read and print voltage, then return
float v = myADC.read_voltage();
printf("%f\n", v);

but this only prints nan or 0.000.

Solution:

mbed doesn’t know the reference voltage for your platform. The easiest method is to provide the referene voltage in the constructor of AnalogIn:

AnalogIn myADC(PA_5, 3.3);

This specifies a reference voltage of 3.3V. While this applies to most applications in their default configuration, note that the reference voltage might be different depending on the configuration of your microcontroller.

In my experience, it’s almost always better to experimentally verify the reference voltage instead of trying to theorize about it if it’s not immediately obvious.

Full example:

#include <mbed.h>

BufferedSerial pc(USBTX, USBRX, 115200); // tx, rx

AnalogIn   myADC(PA_5, 3.3);

FileHandle *mbed::mbed_override_console(int fd) {
    return &pc;
}

int main() {
  while(1) {
    float v = myADC.read_voltage();
    printf("%f\n", v);
    ThisThread::sleep_for(100ms);
  }
}
{
    "target_overrides": {
      "*": {
        "target.printf_lib": "std"
      }
    }
}
Posted by Uli Köhler in C/C++, mbed, PlatformIO

How to fix mbed printf() ignoring decimals in PlatformIO

Problem:

You are using code like

printf("%.2f\n", myFloat);

in your mbed/PlatformIO application, but instead of printing myFloat with 2 decimal places, it always prints it with 6 decimal places (like 0.000000).

Solution:

mbed uses the minimal-printf library by default which is configured to save space on the Microcontroller. Hence, float max decimals support is disabled by default. In order to get all printf features at the expense of more flash usage and much slower executing, us add mbed_app.json in the root directory of the PlatformIO project with "target.printf_lib": "std":

{
    "target_overrides": {
      "*": {
        "target.printf_lib": "std"
      }
    }
}

See the platform configuration option page for more details and similar options.

Posted by Uli Köhler in C/C++, mbed, PlatformIO

How to fix mbed printf() printing literal %f in PlatformIO

Problem:

You are using code like

printf("%f\n", myFloat);

in your mbed/PlatformIO application, but instead of printing myFloat it prints literal %f.

Solution:

mbed uses the minimal-printf library by default which is configured to save space on the Microcontroller. Hence, float support (i.e. %f support) is disabled by default. You need to enable it by adding mbed_app.json in the root directory of the PlatformIO project with "platform.minimal-printf-enable-floating-point": true:

{
    "target_overrides": {
      "*": {
        "platform.minimal-printf-enable-floating-point": true
      }
    }
}

See the platform configuration option page for more details and similar options.

Posted by Uli Köhler in C/C++, mbed, PlatformIO

How to fix mbed error: ‘wait’ was not declared in this scope (PlatformIO)

Problem:

While compiling your mbed / PlatformIO application, you see an error message like

src/actuators.cpp:253:5: error: 'wait' was not declared in this scope
  253 |     wait(1.0);
      |     ^~~~

 

Solution:

wait is an old API and has been deprecated in favour of the C++ standard ThisThread::sleep_for. Use

ThisThread::sleep_for(1s);

 

Posted by Uli Köhler in Embedded, mbed, PlatformIO

mbed STM32 timer interrupt example

You can use the mbed Ticker API to add a timer interrupt to your mbed application. This example will use a Ticker-based timer interrupt to toggle the LED once per second, for example on the STM32F429I-DISCO board:

#include <mbed.h>

DigitalOut led1(LED1);
Ticker ticker;

/**
 * This function will be run once per second
 */
void timerTick() {
  // Toggle LED
  led1 = !led1;
}

int main() {
  ticker.attach(timerTick, 1.0 /* seconds */);

  // What you do in the main loop is not important
  while(1) {
  }
}

 

Posted by Uli Köhler in C/C++, mbed

How to fix Raspberry Pi OpenVPN error “ERROR: Cannot open TUN/TAP dev /dev/net/tun: No such device (errno=19)”

Problem:

You want to setup OpenVPN on your Raspberry Pi but you see an error message like

Fri Jun 26 18:12:35 2020 ERROR: Cannot open TUN/TAP dev /dev/net/tun: No such device (errno=19)
Fri Jun 26 18:12:35 2020 Exiting due to fatal error

Solution:

This error occurs if you’ve installed OpenVPN using sudo apt install -y openvpn but if you didn’t reboot after installing it. In order to fix the issue, reboot using

sudo reboot

 

Posted by Uli Köhler in Linux, Raspberry Pi

How to fix PlatformIO mbed error: ‘Mutex’ does not name a type

Problem:

You are trying to compile your PlatformIO mbed application using Mutexes like

Mutex myLock;

but you see an error message like

src\main.cpp:3:1: error: 'Mutex' does not name a type
 Mutex myLock;
 ^~~~~

Solution:

Add this line to your platformio.ini:

build_flags = -D PIO_FRAMEWORK_MBED_RTOS_PRESENT

This will enable the RTOS features in mbed, including the Mutex.

Posted by Uli Köhler in mbed, PlatformIO

How to fix PlatformIO fatal error: stm32f429i_discovery_lcd.h: No such file or directory

Problem:

You are trying to compile your PlatformIO application using  the LCD_DISCO_F429ZI library, but you see an error message like

 #include "stm32f429i_discovery_lcd.h"
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.
*** [.pio\build\disco_f429zi\src\main.o] Error 1
In file included from .pio\libdeps\disco_f429zi\LCD_DISCO_F429ZI_ID2432\LCD_DISCO_F429ZI.cpp:19:0:
.pio\libdeps\disco_f429zi\LCD_DISCO_F429ZI_ID2432\LCD_DISCO_F429ZI.h:25:10: fatal error: stm32f429i_discovery_lcd.h: No such file or directory

Solution:

First, ensure that BSP_DISCO_F429ZI is listed is library dependency in platformio.ini like this:

[env:disco_f429zi]
platform = ststm32
board = disco_f429zi
framework = mbed
lib_deps =
    LCD_DISCO_F429ZI
    BSP_DISCO_F429ZI

 

Replace the line

#include "stm32f429i_discovery_lcd.h"

in LCD_DISCO_F429ZI.h with

#include "Drivers/BSP/STM32F429I-Discovery/stm32f429i_discovery_lcd.h"

 

Posted by Uli Köhler in C/C++, PlatformIO

How to fix PlatformIO fatal error: ../Fonts/fonts.h: No such file or directory

Problem:

You are trying to compile a PlatformIO application using the BSP_DISCO_F429ZI library, but you see an error message like

In file included from .pio\libdeps\disco_f429zi\BSP_DISCO_F429ZI_ID2208\Drivers\BSP\STM32F429I-Discovery\stm32f429i_discovery_lcd.c:75:0:
.pio\libdeps\disco_f429zi\BSP_DISCO_F429ZI_ID2208\Drivers\BSP\STM32F429I-Discovery\stm32f429i_discovery_lcd.h:49:10: fatal error: ../Fonts/fonts.h: No such file or directory
 #include "../Fonts/fonts.h"
          ^~~~~~~~~~~~~~~~~~
compilation terminated.

Solution:

The BSP_DISCO_F429ZI package includes fonts.h from the wrong directory. Replace

#include "../Fonts/fonts.h"

by

#include "Utilities/Fonts/fonts.h"

in order to fix the issue. You might need to do that multiple times (in multiple files) in order to fix your build.

Posted by Uli Köhler in C/C++, PlatformIO

How to use printf in mbed using STM32F429I-DISC1 and PlatformIO

In PlatformIO, you can directly use printf without any special configuration for the STM32F429-DISC1 discovery board:

#include <mbed.h>

int main() {
  while(1) {
    printf("Hello world\n");
    wait(0.5);
  }
}

This program will print Hello world twice every second. You can watch the output using the PlatformIO Monitor feature.

Posted by Uli Köhler in mbed

How to toggle the STM32F429I-DISCOVERY LED using mbed + PlatformIO

This simple firmare toggles the LED on the STM32F429I-DISC1 discovery board.

#include <mbed.h>

DigitalOut myled(LED1);

int main() {
  while(1) {
    myled = !myled;
    wait(0.5);
  }
}

This will toggle the green (PG13) LED twice per second.

The program is simple: We toggle the LED using myled = !myled; and then use wait(0.5) for 0.5 seconds.

Posted by Uli Köhler in C/C++, mbed