sandbox / simple-mbed-client

A simple interface to mbed Device Connector, where you just declare variables to push them to the cloud.

Dependents:   Wifi_Get_Test_V1 simple-mbed-client-example simple-client-app-shield simple-sensor-client

Fork of simple-mbed-client by Jan Jongboom

TL;DR? See simple-mbed-client-example to get started immediately.

This library is a simpler interface to mbed Client, making it trivial to expose sensors, actuators and other variables to the cloud. It does not require you to change how you write your code. You can take any local variable, swap it out for a call to Simple Mbed Client, and the variable will automatically be synchronised with mbed Cloud.

For example, here's how you expose the value of a light sensor to the cloud:

SimpleMbedClient client;

SimpleResourceInt light_value = client.define_resource("light/0/value", 0);     // create the var

AnalogIn light(A1);

void read_light_sensor() {
    // light_value behaves just like a normal variable that you can read and write to!
    light_value = light.read_u16();
}

// update every second
Ticker t;
t.attach(&read_light_sensor, 1.0f);

Setting up

First import this library to your project. As Simple Mbed Client also needs a way to talk to the outside world, you'll need a NetworkInterface-object. The easiest way is by using the easy-connect library, so add that to your project as well. See the easy-connect docs on how to specify the connectivity method.

We also need a way of authenticating with mbed Cloud. For this we need a security certificate. Go to mbed Cloud, and select 'GET MY DEVICE SECURITY CREDENTIALS'. Save the certificate as security.h in your project folder.

Now we can initiate Simple Mbed Client and connect it to the internet.

#include "mbed.h"
#include "security.h"
#include "easy-connect.h"
#include "simple-mbed-client.h"

SimpleMbedClient client;

DigitalOut led(LED1, 0);

void registered() {
    led = 1;
}

int main() {
    NetworkInterface* network = connect_to_network(); // if connection failed, network will be NULL
    client.setup(network); // returns a bool, check if it's true

    client.on_registered(&registered);

    while (1) {
        wait_ms(25000);
        client.keep_alive();
    }
}

Defining variables

You can define a new variable by a call to client.define_resource. This function takes five arguments:

  1. path - The URL on which your variable is exposed in mbed Cloud. Needs to be three (3) segments, split by a slash (/) in the form of 'sensor/0/value'. The second segment always needs to be numeric.
  2. defaultValue - The default value of the variable. Needs to be either a string or an integer. Depending on the type that you pass in here the type of the variable is defined.
  3. operation - Some variables might be read-only or write-only (seen from the cloud). Use the operation to define these constraints. It's of type M2MBase::Operation. Default is GET_PUT_ALLOWED.
  4. observable - If set to false, cloud applications cannot subscribe to updates on this variable. Default is true.
  5. callback - Function pointer which is called whenever the value of the variable is changed from the cloud.

The type returned by the function is either SimpleResourceInt or SimpleResourceString. You can assign and read from these variables like any normal local variable.

void name_updated(string new_value) {
    printf("Value is now %s\n", new_value.c_str());
}

SimpleResourceString name = client.define_resource("device/0/name", "jan", M2MBase::GET_PUT_ALLOWED, true, &name_updated);

// we can read and write to this variable, e.g.:
stringstream ss;
ss << name;

// or
name = "pietje";

// are all valid

Defining functions

You can define functions, which do not have a value, but can just be invoked from the cloud, by a call to client.define_function. This function takes two arguments:

  1. path - The URL on which your variable is exposed in mbed Cloud. Needs to be three (3) segments, split by a slash (/) in the form of 'sensor/0/value'. The second segment always needs to be numeric.
  2. callback - Function pointer which is invoked when the function is called. Takes in a pointer, which contains the data being passed in from the cloud. 

void play(void* data) {
    if (data) { // data can be NULL!
        // cast it to something useful
    }
}

client.define_function("music/0/play", &play);

Accessing the underlying M2MResource

If you need access to the underlying M2MResource you can do so by calling get_resource on a variable, or by calling client.get_resource if it's a function.

SimpleResourceInt led = client.define_resource("led/0/value", true);

client.define_function("led/0/toggle", &toggleLed);

// now to get the resource
M2MResource* ledResource = led.get_resource();
M2MResource* toggleResource = client.get_resource("led/0/toggle");

Printing variables

Unfortunately printf is kind of dumb, and does not automatically cast the variables. If you want to print any of the Simple Mbed Client variables you'll need to cast yourself.

SimpleResourceInt led = client.define_resource("led/0/value", true);

printf("Value is currently %d\n", static_cast<int>(led));

Event Queue

Simple Mbed Client uses an mbed-events EventQueue - running on a separate RTOS thread - to handle incoming events without blocking the main loop. Both the thread and event queue are created when initializing the library. You can override this behavior by providing your own event queue. In this case no thread is created.

EventQueue myQueue;
SimpleMbedClient client(&myQueue);

You can also use the queue to process your own events, which is very useful when dealing with ISRs. The queue is accessible through the eventQueue() function on the client object and returns a pointer to the queue.

SimpleMbedClient client;

InterruptIn btn(D2);

int main() {
  btn.fall(client.eventQueue()->event(&fall));
}

mbedtls_mbed_client_config.h

Committer:
Jan Jongboom
Date:
2017-03-21
Revision:
23:c89df15e88d2
Parent:
17:200624714d15

File content as of revision 23:c89df15e88d2:

/**
 *  Minimal configuration for using mbedtls as part of mbed-client
 *
 *  NOTE! This is an optimized, minimal configuration for mbed Client.
 *  We know it works with mbed Client but if you want to add more
 *  services/communications to the application yourself - please ensure
 *  you update this configuration accordingly. The default configuration
 *  can be found from mbedTLS Github:
 *
 *  https://github.com/ARMmbed/mbedtls/blob/development/include/mbedtls/config.h
 *
 *
 *  Copyright (C) 2006-2016, ARM Limited, All Rights Reserved
 *  SPDX-License-Identifier: Apache-2.0
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
 *  not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *  This file is part of mbed TLS (https://tls.mbed.org)
 */


#ifndef MBEDTLS_CUSTOM_CONFIG_H
#define MBEDTLS_CUSTOM_CONFIG_H

/* Enable entropy for K64F and K22F. This means entropy is disabled for all other targets. */
/* Do **NOT** deploy this code in production on other targets! */
/* See https://tls.mbed.org/kb/how-to/add-entropy-sources-to-entropy-pool */
#if defined(TARGET_K64F) || defined(TARGET_K22F)
#undef MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES
#undef MBEDTLS_TEST_NULL_ENTROPY
#endif

/* System support */
#define MBEDTLS_HAVE_ASM

/* mbed TLS feature support */
#define MBEDTLS_ECP_DP_SECP256R1_ENABLED
#define MBEDTLS_ECP_NIST_OPTIM
#define MBEDTLS_SSL_MAX_FRAGMENT_LENGTH
#define MBEDTLS_SSL_PROTO_TLS1_2
#define MBEDTLS_SSL_PROTO_DTLS
#define MBEDTLS_SSL_DTLS_ANTI_REPLAY
#define MBEDTLS_SSL_DTLS_HELLO_VERIFY
#define MBEDTLS_SSL_EXPORT_KEYS

/* mbed TLS modules */
#define MBEDTLS_AES_C
#define MBEDTLS_ASN1_PARSE_C
#define MBEDTLS_ASN1_WRITE_C
#define MBEDTLS_BIGNUM_C
#define MBEDTLS_CIPHER_C
#define MBEDTLS_CTR_DRBG_C
#define MBEDTLS_ECP_C
#define MBEDTLS_ENTROPY_C
#define MBEDTLS_MD_C
#define MBEDTLS_OID_C
#define MBEDTLS_PK_C
#define MBEDTLS_PK_PARSE_C
#define MBEDTLS_SHA256_C
#define MBEDTLS_SSL_COOKIE_C
#define MBEDTLS_SSL_CLI_C
#define MBEDTLS_SSL_SRV_C
#define MBEDTLS_SSL_TLS_C

// XXX mbedclient needs these: mbedtls_x509_crt_free, mbedtls_x509_crt_init, mbedtls_x509_crt_parse
#define MBEDTLS_X509_USE_C
#define MBEDTLS_X509_CRT_PARSE_C

// XXX: clean these up!!
#define MBEDTLS_SHA512_C
#define MBEDTLS_ECDH_C
#define MBEDTLS_GCM_C

#define MBEDTLS_ECDH_C
#define MBEDTLS_ECDSA_C
#define MBEDTLS_X509_CRT_PARSE_C

// Remove RSA, save 20KB at total
#undef MBEDTLS_RSA_C
#undef MBEDTLS_KEY_EXCHANGE_ECDHE_RSA_ENABLED

// Remove error messages, save 10KB of ROM
#undef MBEDTLS_ERROR_C

// Remove selftesting and save 11KB of ROM
#undef MBEDTLS_SELF_TEST

// Reduces ROM size by 30 kB
#undef MBEDTLS_ERROR_STRERROR_DUMMY
#undef MBEDTLS_VERSION_FEATURES
#undef MBEDTLS_DEBUG_C

// needed for parsing the certificates
#define MBEDTLS_PEM_PARSE_C
// dep of the previous
#define MBEDTLS_BASE64_C

// Reduce IO buffer to save RAM, default is 16KB
#define MBEDTLS_SSL_MAX_CONTENT_LEN 2048

// define to save 8KB RAM at the expense of ROM
#undef MBEDTLS_AES_ROM_TABLES

// Save ROM and a few bytes of RAM by specifying our own ciphersuite list
#define MBEDTLS_SSL_CIPHERSUITES MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,MBEDTLS_TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256

#include "mbedtls/check_config.h"

#endif /* MBEDTLS_CUSTOM_CONFIG_H */