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Bluetoe implements a GATT server with a very low memory footprint and a convenient C++ interface. Bluetoe makes things easy but gives you the opportunity to fiddle with all the low-level GATT details if necessary. Bluetoe's primary target is very small microcontrollers. Here is a complete example of a small GATT server that allows a client to controll an IO pin, running on a nRF52832:
#include <bluetoe/server.hpp>
#include <bluetoe/device.hpp>
#include <nrf.h>
using namespace bluetoe;
// LED1 on a nRF52 eval board
static constexpr int io_pin = 17;
static std::uint8_t io_pin_write_handler( bool state )
{
// On an nRF52 eval board, the pin is connected to the LED's cathode. This inverts the logic.
NRF_GPIO->OUT = state
? NRF_GPIO->OUT & ~( 1 << io_pin )
: NRF_GPIO->OUT | ( 1 << io_pin );
return error_codes::success;
}
using blinky_server = server<
service<
service_uuid< 0xC11169E1, 0x6252, 0x4450, 0x931C, 0x1B43A318783B >,
characteristic<
requires_encryption,
free_write_handler< bool, io_pin_write_handler >
>
>
>;
blinky_server gatt;
device< blinky_server > gatt_srv;
int main()
{
// Init GPIO pin
NRF_GPIO->PIN_CNF[ io_pin ] =
( GPIO_PIN_CNF_DRIVE_S0H1 << GPIO_PIN_CNF_DRIVE_Pos ) |
( GPIO_PIN_CNF_DIR_Output << GPIO_PIN_CNF_DIR_Pos );
for ( ;; )
gatt_srv.run( gatt );
}
http://torstenrobitzki.github.io/bluetoe/
Bluetoe ships with its own fully-usable link layer based on the nRF52832. The link layer implementation is based and tested on an abstract device called a scheduled radio, and should be easy to port to similar hardware. As Bluetoe is a GATT server implementation, only parts of the link layer relevant to GATT have been implemented. Bluetoe can be easily adapted to any other existing L2CAP implementation (those based on HCI, for example).
The following table shows the list of supported GATT procedures, along with and their current and planned implementation status:
Feature | Sub-Procedure | Status |
---|---|---|
Server Configuration | Exchange MTU | implemented |
Primary Service Discovery | Discover All Primary Services | implemented |
Discover Primary Service By Service UUID | implemented | |
Relationship Discovery | Find Included Services | implemented |
Declare Secondary Services | implemented | |
Characteristic Discovery | Discover All Characteristic of a Service | implemented |
Discover Characteristic by UUID | implemented | |
Characteristic Descriptor Discovery | Discover All Characteristic Descriptors | implemented |
Characteristic Value Read | Read Characteristic Value | implemented |
Read Using Characteristic UUID | implemented | |
Read Long Characteristic Value | implemented | |
Read Multiple Characteristic Values | implemented | |
Characteristic Value Write | Write Without Response | implemented |
Signed Write Without Response | not planned | |
Write Characteristic Value | implemented | |
Write Long Characteristic Values | implemented | |
Characteristic Value Reliable Writes | implemented | |
Characteristic Value Notification | Notifications | implemented |
Characteristic Value Indication | Indications | implemented |
Characteristic Descriptor Value Read | Read Characteristic Descriptors | implemented |
Read Long Characteristic Descriptors | implemented | |
Characteristic Descriptor Value Write | Write Characteristic Descriptors | implemented |
Write Long Characteristic Descriptors | implemented | |
Cryptography | Encryption | implemented |
Authentication | planned |
This is the current state of implemented Advertising Data:
Advertising Data | Format | Status |
---|---|---|
Service UUID | Incomplete List of 16-bit Service UUIDs | implemented |
Complete List of 16-bit Service UUIDs | implemented | |
Incomplete List of 32-bit Service UUIDs | not planned | |
Complete List of 32-bit Service UUIDs | not planned | |
Incomplete List of 128-bit Service UUIDs | implemented | |
Complete List of 128-bit Service UUIDs | implemented | |
Local Name | Shortened Local Name | implemented |
Complete Local Name | implemented | |
Flags | Flags | implemented |
Manufacturer Specific Data | Manufacturer Specific Data | planned |
TX Power Level | TX Power Level | planned |
Secure Simple Pairing Out of Band | not planned | |
Security Manager Out of Band | not planned | |
Security Manager TK Value | not planned | |
Slave Connection Interval Range | not planned | |
Service Solicitation | not planned | |
Service Data | not planned | |
Appearance | Appearance | implemented |
LE Role | LE Role | planned |
This is the current state of the Link Layer implementation:
Aspect | Feature | Status |
---|---|---|
Roles | Slave Role | implemented |
Master Role | not planned | |
Advertising | connectable undirected advertising | implemented |
connectable directed advertising | implemented | |
non-connectable undirected advertising | implemented | |
scannable undirected advertising | implemented | |
Device Filtering | implemented | |
Connections | Single Connection | implemented |
Multiple Connection | not planned | |
Connection | Slave Latency | planned |
Feature Support | LE Encryption | implemented |
Connection Parameters Request Procedure | implemented | |
Extended Reject Indication | planned | |
Slave-initiated Features Exchange | planned | |
LE Ping | implemented | |
LE Data Packet Length Extension | planned | |
LL Privacy | not planned | |
Extended Scanner Filter Policies | not planned |
Pull requests are welcome.
All measurements were done without any traffic and a slave latency of 0. Average current was measured using various connection intervals.
Calibrated RC Sleep Clock (500ppm) (13608 Bytes binary size)
Crystal Oscilator Sleep Clock (20ppm) (13364 Bytes binary size)
Calibrated RC Sleep Clock (500ppm) (22848 Bytes binary size)
Crystal Oscilator Sleep Clock (20ppm) (22608 Bytes binary size)
Synthesized Sleep Clock (40ppm) (22596 Bytes binary size)
Old radio implementation (40ppm) (22212 Bytes binary size)
Calibrated RC Sleep Clock (500ppm / 1ms HFXO startup time) (21880 Bytes binary size)
Calibrated RC Sleep Clock (500ppm / 0.3ms HFXO startup time) (21880 Bytes binary size)