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ESP32 e IDF: Utilizando Bluetooth Classic

ESP32 e IDF: Utilizando Bluetooth Classic
Pedro Minatel
Por: Pedro Minatel
Dia 29/12/2017 - 17h12

Como utilizar Bluetooth Classic no ESP32 e BTstack

Muitas pessoas são movidas por desafios, e eu não sou diferente. Desde que eu recebi o meu primeiro ESP32 da SparkFun, fiquei interessado mais na questão de ter um Bluetooth junto com o WiFi do que qualquer outro atributo do ESP32. E ai vieram as primeiras decepções, que muitos usuários do ESP32 já estavam enfrentando. Além da falta de documentação em relação ao uso do Bluetooth, algumas pessoas estavam relatando que a Espressif ainda não tinha terminado toda a implementação da pilha, parei de me interessar em fazer funcionar. Eis que surge uma oportunidade de usar o Bluetooth no ESP32. Fiz a devida atualização da plataforma ESP-IDF, que já tratamos aqui anteriormente e comecei a ler novamente a documentação. Descobri que ainda estavam faltando alguns detalhes e que não seria tarefa trivial utilizar, mesmo que alguns testes dos exemplos prontos funcionavam com BLE, mas não com Bluetooth Classic. Não poderia utilizar a pilha da Espressif. Na minha busca em alternativas, me deparei com a BTstack da BlueKitchen, que é uma pilha de Bluetooth que suporta SPP (Serial Port Profile) e tem suporte para o ESP32.

Instalando a BTstack

Para instalar a BTstack, devemos antes instalar o ESP-IDF, que pode ser feito por este link. Feita a instalação do ESP-IDF, devemos fazer o clone do repositorio na mesma pasta em que está a pasta esp-idf, no meu caso a pasta /home/pedro/esp. No terminal:

$ git clone https://github.com/bluekitchen/btstack.git

Vá para a pasta btstack/port/esp32/

$ cd btstack/port/esp32/

Execute o comando:

./integrate_btstack.py

Neste ponto, a BTstack deverá aparecer dentro da pasta components do ESP-IDF ../esp/esp-idf/components/btstack/

Testando a Btstack

Durante esse processo de instalação, foram criados os exemplos na seguinte pasta: ../esp/btstack/port/esp32/example/ Neste diretório temos os exemplos para fazer diversos testes, mas vamos focar no Bluetooth Classic com SPP, muito utilizado em projetos maker. O exemplo “spp_counter”, será o nosso exemplo base, e com algumas alterações podemos realizar os mais diversos tipos de integração.

Código fonte de teste

 

/*
* Copyright (C) 2014 BlueKitchen GmbH
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the copyright holders nor the names of
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
* 4. Any redistribution, use, or modification is done solely for
* personal benefit and not for any commercial purpose or for
* monetary gain.
*
* THIS SOFTWARE IS PROVIDED BY BLUEKITCHEN GMBH AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
* RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
* THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* Please inquire about commercial licensing options at
* contact@bluekitchen-gmbh.com
*
*/

#define __BTSTACK_FILE__ "spp_counter.c"

// *****************************************************************************
/* EXAMPLE_START(spp_counter): SPP Server - Heartbeat Counter over RFCOMM
*
* @text The Serial port profile (SPP) is widely used as it provides a serial
* port over Bluetooth. The SPP counter example demonstrates how to setup an SPP
* service, and provide a periodic timer over RFCOMM.
*/
// *****************************************************************************

#include 
#include 
#include 
#include 
#include 

#include "btstack.h"

#define RFCOMM_SERVER_CHANNEL 1
#define HEARTBEAT_PERIOD_MS 1000

static char lineBuffer[30];

static void packet_handler (uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size);

static uint16_t rfcomm_channel_id;
static uint8_t spp_service_buffer[150];
static btstack_packet_callback_registration_t hci_event_callback_registration;


/* @section SPP Service Setup
*s
* @text To provide an SPP service, the L2CAP, RFCOMM, and SDP protocol layers
* are required. After setting up an RFCOMM service with channel nubmer
* RFCOMM_SERVER_CHANNEL, an SDP record is created and registered with the SDP server.
* Example code for SPP service setup is
* provided in Listing SPPSetup. The SDP record created by function
* spp_create_sdp_record consists of a basic SPP definition that uses the provided
* RFCOMM channel ID and service name. For more details, please have a look at it
* in \path{src/sdp_util.c}.
* The SDP record is created on the fly in RAM and is deterministic.
* To preserve valuable RAM, the result could be stored as constant data inside the ROM.
*/

/* LISTING_START(SPPSetup): SPP service setup */
static void spp_service_setup(void){

// register for HCI events
hci_event_callback_registration.callback = &packet_handler;
hci_add_event_handler(&hci_event_callback_registration);

l2cap_init();

rfcomm_init();
rfcomm_register_service(packet_handler, RFCOMM_SERVER_CHANNEL, 0xffff); // reserved channel, mtu limited by l2cap

// init SDP, create record for SPP and register with SDP
sdp_init();
memset(spp_service_buffer, 0, sizeof(spp_service_buffer));
spp_create_sdp_record(spp_service_buffer, 0x10001, RFCOMM_SERVER_CHANNEL, "SPP Counter");
sdp_register_service(spp_service_buffer);
printf("SDP service record size: %u\n", de_get_len(spp_service_buffer));
}
/* LISTING_END */

/* @section Bluetooth Logic
* @text The Bluetooth logic is implemented within the
* packet handler, see Listing SppServerPacketHandler. In this example,
* the following events are passed sequentially:
* - BTSTACK_EVENT_STATE,
* - HCI_EVENT_PIN_CODE_REQUEST (Standard pairing) or
* - HCI_EVENT_USER_CONFIRMATION_REQUEST (Secure Simple Pairing),
* - RFCOMM_EVENT_INCOMING_CONNECTION,
* - RFCOMM_EVENT_CHANNEL_OPENED,
* - RFCOMM_EVETN_CAN_SEND_NOW, and
* - RFCOMM_EVENT_CHANNEL_CLOSED
*/

/* @text Upon receiving HCI_EVENT_PIN_CODE_REQUEST event, we need to handle
* authentication. Here, we use a fixed PIN code "0000".
*
* When HCI_EVENT_USER_CONFIRMATION_REQUEST is received, the user will be
* asked to accept the pairing request. If the IO capability is set to
* SSP_IO_CAPABILITY_DISPLAY_YES_NO, the request will be automatically accepted.
*
* The RFCOMM_EVENT_INCOMING_CONNECTION event indicates an incoming connection.
* Here, the connection is accepted. More logic is need, if you want to handle connections
* from multiple clients. The incoming RFCOMM connection event contains the RFCOMM
* channel number used during the SPP setup phase and the newly assigned RFCOMM
* channel ID that is used by all BTstack commands and events.
*
* If RFCOMM_EVENT_CHANNEL_OPENED event returns status greater then 0,
* then the channel establishment has failed (rare case, e.g., client crashes).
* On successful connection, the RFCOMM channel ID and MTU for this
* channel are made available to the heartbeat counter. After opening the RFCOMM channel,
* the communication between client and the application
* takes place. In this example, the timer handler increases the real counter every
* second.
*
* RFCOMM_EVENT_CAN_SEND_NOW indicates that it's possible to send an RFCOMM packet
* on the rfcomm_cid that is include

*/

/* LISTING_START(SppServerPacketHandler): SPP Server - Heartbeat Counter over RFCOMM */
static void packet_handler (uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
UNUSED(channel);

/* LISTING_PAUSE */
bd_addr_t event_addr;
uint8_t rfcomm_channel_nr;
uint16_t mtu;
int i;

switch (packet_type) {
case HCI_EVENT_PACKET:
switch (hci_event_packet_get_type(packet)) {
/* LISTING_RESUME */
case HCI_EVENT_PIN_CODE_REQUEST:
// inform about pin code request
printf("Pin code request - using '0000'\n");
hci_event_pin_code_request_get_bd_addr(packet, event_addr);
gap_pin_code_response(event_addr, "0000");
break;

case HCI_EVENT_USER_CONFIRMATION_REQUEST:
// ssp: inform about user confirmation request
printf("SSP User Confirmation Request with numeric value '%06"PRIu32"'\n", little_endian_read_32(packet, 8));
printf("SSP User Confirmation Auto accept\n");
break;

case RFCOMM_EVENT_INCOMING_CONNECTION:
// data: event (8), len(8), address(48), channel (8), rfcomm_cid (16)
rfcomm_event_incoming_connection_get_bd_addr(packet, event_addr);
rfcomm_channel_nr = rfcomm_event_incoming_connection_get_server_channel(packet);
rfcomm_channel_id = rfcomm_event_incoming_connection_get_rfcomm_cid(packet);
printf("RFCOMM channel %u requested for %s\n", rfcomm_channel_nr, bd_addr_to_str(event_addr));
rfcomm_accept_connection(rfcomm_channel_id);
break;

case RFCOMM_EVENT_CHANNEL_OPENED:
// data: event(8), len(8), status (8), address (48), server channel(8), rfcomm_cid(16), max frame size(16)
if (rfcomm_event_channel_opened_get_status(packet)) {
printf("RFCOMM channel open failed, status %u\n", rfcomm_event_channel_opened_get_status(packet));
} else {
rfcomm_channel_id = rfcomm_event_channel_opened_get_rfcomm_cid(packet);
mtu = rfcomm_event_channel_opened_get_max_frame_size(packet);
printf("RFCOMM channel open succeeded. New RFCOMM Channel ID %u, max frame size %u\n", rfcomm_channel_id, mtu);
}
break;
case RFCOMM_EVENT_CAN_SEND_NOW:
rfcomm_send(rfcomm_channel_id, (uint8_t*) lineBuffer, strlen(lineBuffer));
break;

/* LISTING_PAUSE */
case RFCOMM_EVENT_CHANNEL_CLOSED:
printf("RFCOMM channel closed\n");
rfcomm_channel_id = 0;
break;

default:
break;
}
break;

case RFCOMM_DATA_PACKET:
printf("Recebido: ");

for (i=0;i

 

Para testar o funcionamento, utilizei o programa para Android “Bluetooth Terminal HC-05”.

 

Conclusão

Pelos teste que fiz, pude notar que a BTstack foi a melhor opção para SPP em modo Bluetooth Classic. Não posso dizer em relação aos outros exemplos pois não utilizei a ponto de tirar alguma conclusão.

O que posso dizer é que eu fiquei muito satisfeito com a documentação e com os exemplos prontos que a Bluekitchen disponibilizou.

Happy Hacking and Happy 2018!

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