Blynk

Github Repo	C Header	C source	JS source
mongoose-os-libs/blynk	mgos_blynk.h		api_blynk.js

This Mongoose OS library allows your device remote control via the Blynk platform. It currently only works with Blynk Legacy and is not compatible with Blynk IoT. Device side logic could be implemented in either C/C++ or JavaScript.

Blynk is a platform with iOS and Android apps to control Arduino, Raspberry Pi and the likes over the Internet.

See example video at:

How to use this library

In your Mongoose OS app, edit mos.yml file and add a reference to this library. See an example blynk app that does that.

Device configuration

This library adds blynk configuration section to the device:

mos config-get blynk
{
  "auth": "YOUR_BLYNK_AUTH_TOKEN",
  "enable": true,
  "server": "blynk-cloud.com:8442"
}

In order for your device to authenticate with Blynk cloud, either use Web UI to change the blynk.auth value, or in a terminal:

mos config-set blynk.auth=YOUR_BLYNK_AUTH_TOKEN

---

Blynk API.

This library supports only a subset of Blynk protocol - namely, virtual pin reading and virtual pin writing. That is enough to implement a very wide class of applications. It currently only works with Blynk Legacy and is not compatible with Blynk IoT.

---

(*blynk_handler_t)

typedef void (*blynk_handler_t)(struct mg_connection *, const char *cmd,
                                int pin, int val, int id, void *user_data);

Blynk event handler signature.

blynk_set_handler

void blynk_set_handler(blynk_handler_t func, void *user_data);

Set Blynk event handler. Everytime a Blynk event is raised, func will be called to treat that Event. Example:

// Defines Default Handler Func, sets that func using blynk_set_handler. The handler Func checks if there is a Virtual Read command and if true, sends virtual write that sets s_read_virtual_pin to 1
void default_blynk_handler(struct mg_connection *c, const char *cmd,
                                  int pin, int val, int id, void *user_data) {
  if (strcmp(cmd, "vr") == 0) {
    if (pin == s_read_virtual_pin) {
      blynk_virtual_write(c, s_read_virtual_pin, 1, id);
    }
  } 
  (void) user_data;
}
enum mgos_app_init_result mgos_app_init(void) {
  blynk_set_handler(default_blynk_handler, NULL);
  return MGOS_APP_INIT_SUCCESS;
}

blynk_send

void blynk_send(struct mg_connection *c, uint8_t type, uint16_t id,
                const void *data, uint16_t len);

Send data to the Blynk server. c is a network connection which is passed to the handler registered with blynk_set_handler. type is one of the following:

• BLYNK_RESPONSE
• BLYNK_LOGIN
• BLYNK_PING
• BLYNK_HARDWARE

id is the internal blynk message id; if undefined it will be autogenerated. data holds a message to send. len holds the length of a message to send.

blynk_printf

void blynk_printf(struct mg_connection *c, uint8_t type, uint16_t id,
                  const char *fmt, ...);

Same as as blynk_send(), formats message using printf() semantics.

blynk_virtual_write

void blynk_virtual_write(struct mg_connection *c, int pin, float val, int id);

Send a virtual write command. If id is undefined, it will be autogenerated. This is a helper function that uses blynk_send().

JS API

---

Blynk.send

Blynk.send(conn, type, msg, id)

Send raw message to Blynk server.

conn is a network connection which is passed to the handler registered with Blynk.setHandler. type is one of the following:

• Blynk.TYPE_RESPONSE
• Blynk.TYPE_LOGIN
• Blynk.TYPE_PING
• Blynk.TYPE_HARDWARE

msg is a string with the data to send. id is the internal blynk message id; if undefined it will be autogenerated.

Return value: none. Example:

// Send "virtual write" command manually: write "1" to pin "16"
Blynk.send(conn, Blynk.TYPE_HARDWARE, 'vw\x0016\x001');

Blynk.virtualWrite

Blynk.virtualWrite(conn, pin, val, id)

Write to the virtual pin. If id is undefined, it will be autogenerated. This is a helper function that uses Blynk.send(). Return value: none. Example:

// Send "virtual write" command: write "1" to pin "16"
Blynk.virtualWrite(conn, 16, 1);

Blynk.setHandler

Blynk.setHandler(handler, userdata)

Set handler for the virtual pin reads / writes.

Example:

Blynk.setHandler(function(conn, cmd, pin, val, id) {
  print(cmd, pin, val);
}, null);

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