netdev BLE mode¶
BLE adaption of netdev.
About¶
BLE defines a very specific environment for the used radio, both in terms of communication sequences and in terms of timings. BLE communication is structured in so called events, where each event is a sequence of request and reply packets send between two peers. A radio context (frequency, CRC initializer, and access address) is used throughout such an event and typically changed for the next one. In addition, the timing of the packets sent in a sequence is fixed to an inter-frame-spacing of exactly 150us.
To cater with these specific attributes of BLE, this interface tailors the generic netdev interface to be used for BLE radios.
Interface Adaption / Netdev Interpretation¶
Transmission Sequence Based Approach¶
To be able to handle the exact inter-packet-spacing if 150us seconds, this interface expects the device driver to stay in a continuous alternating RX-TX sequence, until it is manually aborted. While in this sequence, the radio driver needs to take care of switching to RX mode 150us after sending the last packet, and to send the next packet 150us after the last packet was received.
Such a transmission sequence is started by calling either the radio’s send or receive function while the radio is in idle/standby mode.
Once a transmission sequence is in progress, the next packet to be send, or the next reception buffer to be used is specified also using the send/recv functions. They should be called in the event_callback right after the last transmission (RX or TX) was finished.
The transmission sequence is aborted by calling netdev_ble_stop(dev) (netdev->set(dev, NETOPT_BLE_CTX, NULL, 0)). This will put the radio back into idle/standby mode.
Radio Context¶
As BLE uses time sliced channel hopping, the used channel needs to be set regularly. Additionally, also the used access address and the CRC initializer need to be set regularly, as they differ for different BLE connections. To make setting these values more efficient, this interface combines these three values in to a so called radio context and adds a netopt option to set all three values at once using netdev_ble_set_ctx(dev, ctx) (netdev->set(dev, NETOPT_BLE_CTX, ctx, sizeof(netdev_ble_ctx_t))).
Transmission Sequence Based Approach¶
To be able to handle the exact inter-packet-spacing if 150us seconds, this interface expects the device driver to stay in a continuous alternating RX-TX sequence, until it is manually aborted. While in this sequence, the radio driver needs to take care of switching to RX mode 150us after sending the last packet, and to send the next packet 150us after the last packet was received.
Such a transmission sequence is started by calling either the radio’s send or receive function while the radio is in idle/standby mode.
Once a transmission sequence is in progress, the next packet to be send, or the next reception buffer to be used is specified also using the send/recv functions. They should be called in the event_callback right after the last transmission (RX or TX) was finished.
The transmission sequence is aborted by calling netdev_ble_stop(dev) (netdev->set(dev, NETOPT_BLE_CTX, NULL, 0)). This will put the radio back into idle/standby mode.
Radio Context¶
As BLE uses time sliced channel hopping, the used channel needs to be set regularly. Additionally, also the used access address and the CRC initializer need to be set regularly, as they differ for different BLE connections. To make setting these values more efficient, this interface combines these three values in to a so called radio context and adds a netopt option to set all three values at once using netdev_ble_set_ctx(dev, ctx) (netdev->set(dev, NETOPT_BLE_CTX, ctx, sizeof(netdev_ble_ctx_t))).
Implementation Status and Limitations¶
- This interface works for memory mapped radios only (no support for bus-connected devices). This is mainly for timing reasons.
- No support for LE Data Length Extension (bigger packet size), yet
-
int
netdev_ble_send(netdev.h::netdev_t* dev, netdev_ble_pkt_t * pkt)¶ Send the given packet on the next occasion.
If a transmission sequence is in progress, the given packet will be send after 150us after receptions of the last packet. If no sequence is currently active, the packet will be send immediately and a new transmission sequence is started.
Note
Call this function only to start a new transmission sequence (radio is currently idle), or right after a packet was received. If called at any other point in time, the behavior is undefined.
Parameters
dev: radio to use for sending pkt: data to send Return values
- 0 on success
< 0on error
-
int
netdev_ble_recv(netdev.h::netdev_t* dev, netdev_ble_pkt_t * pkt)¶ Start listening for an incoming packet and write it into
pkt.If a transmission sequence is in progress, the radio will use the given buffer for reception when it goes in to RX mode 150us after sending the last packet. If no sequence is in progress, the radio will go into RX mode immediately (using the given RX buffer), and a new transmission sequence is started.
Note
Call this function only to start a new transmission sequence (radio is currently idle), or right after a packet was sent. If called at any other point in time, the behavior is undefined.
Parameters
dev: radio to use for receiving pkt: buffer to write new packet to Return values
- 0 on success
< 0on error
-
void
netdev_ble_set_ctx(netdev.h::netdev_t* dev, netdev_ble_ctx_t * ctx)¶ Set the radio context for the given radio device.
Parameters
dev: target radio device ctx: new radio context (CRC, channel, access address)
-
void
netdev_ble_stop(netdev.h::netdev_t* dev)¶ Stop the ongoing RX/TX sequence.
Note
This function has not effect if the radio is in the middle of a data transfer
Parameters
dev: target radio device
-
NETDEV_BLE_PDU_MAXLEN¶ Maximum payload length of a standard BLE packet.
1
(37U)
-
NETDEV_BLE_CRC_MASK¶ Mask for the actual (3 byte) CRC data in the context’s CRC field.
1
(0x00ffffff)
-
NETDEV_BLE_CRC_OK¶ Flag for marking a correct CRC on packet reception.
1
(0x80000000)