Single-wire peer-to-peer bus
A single-wire peer-to-peer (P2P) bus apparatus is provided. The single-wire P2P bus apparatus includes a first peer device and a second peer device(s) coupled to a single-wire bus that correspond to a first bus access priority and a second bus access priority(s), respectively. Any of the first peer device and the second peer device(s) can contend for access to the single-wire bus by asserting a bus contention indication(s) when the single-wire bus is in a defined bus state. A winner for the single-wire bus may be a peer device having a highest bus access priority among those peer devices asserting the bus contention indication(s). In this regard, any peer device on the single-wire bus can have a chance to initiate communications over the single-wire bus, thus making it possible for the single-wire bus to function based on bidirectional P2P bus architecture capable of supporting more application and/or deployment scenarios.
1. A single-wire peer-to-peer (P2P) bus apparatus comprising:
a first peer device coupled to a single-wire bus and assigned a first bus access priority, the first peer device is configured to broadcast an opening start-of-sequence (SOS) sequence configured to start telegram communication and provide a timing reference for at least one second peer device; and
the at least one second peer device coupled to the single-wire bus and assigned at least one second bus access priority lower than the first bus access priority;
wherein at least one selected peer device among the first peer device and the at least one second peer device is configured to:
assert a bus contention indication when the single-wire bus is in a defined bus state configured to permit bus contention;
determine whether the bus contention indication is successful based on the first bus access priority of the first peer device and the at least one second bus access priority of the at least one second peer device; and
communicate over the single-wire bus in response to the bus contention indication being successful.
2. The single-wire P2P bus apparatus of claim 1 further comprising the single-wire bus.
3. The single-wire P2P bus apparatus of claim 1 wherein the defined bus state corresponds to an idle state configured to enable communication between the first peer device and the at least one second peer device.
4. The single-wire P2P bus apparatus of claim 1 wherein the single-wire bus is maintained at a bus voltage during the defined bus state.
5. The single-wire P2P bus apparatus of claim 4 wherein the at least one selected peer device is further configured to assert the bus contention indication by pulling down the bus voltage of the single-wire bus to a predefined threshold and subsequently restoring the single-wire bus to the bus voltage.
6. The single-wire P2P bus apparatus of claim 5 wherein the first peer device is further configured to broadcast the opening SOS sequence immediately upon the at least one selected peer device restoring the single-wire bus to the bus voltage.
7. The single-wire P2P bus apparatus of claim 5 wherein the first peer device is further configured to broadcast the opening SOS sequence after a hysteresis period from a time at which the at least one selected peer device restores the single-wire bus to the bus voltage.
8. The single-wire P2P bus apparatus of claim 5 wherein the first peer device is further configured to broadcast a first bus request telegram over the single-wire bus immediately after communicating the opening SOS sequence.
9. The single-wire P2P bus apparatus of claim 8 wherein the at least one second peer device is configured to broadcast at least one second bus request telegram over the single-wire bus immediately after the first peer device broadcasts the first bus request telegram.
10. The single-wire P2P bus apparatus of claim 9 wherein the first peer device and the at least one second peer device are configured to broadcast the first bus request telegram and the at least one second bus request telegram, respectively, according to an order established by the first bus access priority and the at least one second bus access priority.
11. The single-wire P2P bus apparatus of claim 9 wherein each of the first bus request telegram and the at least one second bus request telegram comprises a respective data field configured to indicate a respective intention to access the single-wire bus.
12. The single-wire P2P bus apparatus of claim 11 wherein each of the first bus request telegram and the at least one second bus request telegram further comprises a respective parity field subsequent to the respective data field.
13. The single-wire P2P bus apparatus of claim 12 wherein each of the first bus request telegram and the at least one second bus request telegram further comprises a respective bus park field subsequent to the respective parity field.
14. The single-wire P2P bus apparatus of claim 9 wherein the at least one selected peer device is further configured to:
determine an end of the at least one second bus request telegram; and
communicate one or more protocol telegrams subsequent to the end of the at least one second bus request telegram in response to the bus contention indication being successful.
15. The single-wire P2P bus apparatus of claim 9 wherein the first peer device is further configured to broadcast a closing SOS sequence subsequent to the at least one second bus request telegram.
16. The single-wire P2P bus apparatus of claim 15 wherein the opening SOS sequence is configured to be identical to the closing SOS sequence.
17. The single-wire P2P bus apparatus of claim 15 wherein the opening SOS sequence is configured to be different from the closing SOS sequence.
18. The single-wire P2P bus apparatus of claim 15 wherein the first peer device is further configured to broadcast a bus park sequence subsequent to the closing SOS sequence.
19. The single-wire P2P bus apparatus of claim 18 wherein the at least one selected peer device is further configured to communicate one or more protocol telegrams subsequent to the bus park sequence in response to the bus contention indication being successful.