GATT(GENERIC ATTRIBUTE PROFILE) describes a service framework using the Attribute Protocol for discovering services, and for reading and writing characteristic values on a peer device. There are 11 features defined in the GATT Profile, and each of the features is mapped to procedures and sub-procedures:
| Item No. | Feature | Sub-Procedure | nimBLE command |
|---|---|---|---|
| 1 | Server Configuration | Exchange MTU | b mtu |
| 2 | Primary Service Discovery | Discover All Primary Services | b disc svc conn=x |
| Discover Primary Services By Service UUID | b disc svc conn=x uuid=x | ||
| 3 | Relationship Discovery | Find Included Services | b find inc_svcs conn=x start=x end=x |
| 4 | Characteristic Discovery | Discover All Characteristic of a Service | b disc chr conn=x start=x end=x |
| Discover Characteristic by UUID | b disc chr conn=x start=x end=x uuid=x | ||
| 5 | Characteristic Descriptor Discovery | Discover All Characteristic Descriptors | b disc dsc conn=x start=x end=x |
| 6 | Reading a Characteristic Value | Read Characteristic Value | b read conn=x attr=x |
| Read Using Characteristic UUID | b read conn=x start=x end=x uuid=x | ||
| Read Long Characteristic Values | b read conn=x attr=x long=1 | ||
| Read Multiple Characteristic Values | b read conn=x attr=x attr=y attr=z | ||
| 7 | Writing a Characteristic Value | Write Without Response | b write conn=x value=0xXX:0xXX no_rsp=1 |
| Signed Write Without Response | NOT SUPPORTED | ||
| Write Characteristic Value | b write conn=x attr=x value=0xXX:0xXX | ||
| Write Long Characteristic Values | b write conn=x attr=x value=0xXX:0xXX long=1 | ||
| Characteristic Value Reliable Writes | b write conn=x attr=x value=0xXX:0xXX attr=y value=0xYY:0xYY | ||
| 8 | Notification of a Characteristic Value | Notifications | Write 0x01:0x00 to CLIENT CONFIGURATION characteristic |
| 9 | Indication of a Characteristic Value | Indications | Write 0x02:0x00 to CLIENT CONFIGURATION characteristic |
| 10 | Reading a Characteristic Descriptor | Read Characteristic Descriptors | b read conn=x attr=x |
| Read Long Characteristic Descriptors | b read conn=x attr=x long=1 | ||
| 11 | Writing a Characteristic Descriptor | Write Characteristic Descriptors | b write conn=x value=0xXX:0xXX |
| Write Long Characteristic Descriptors | b write conn=x value=0xXX:0xXX long=1 |
Assuming you have discovered and established a BLE connection with at least one peer device (as explained earlier in API for bletiny app, you can find out what characteristics and services are available over these connections. Here is a recap.
To show established connections:
b show conn
To show discovered services, characteristics, and descriptors:
b show chr
To show connection RSSI:
b show rssi conn=x