Image-capturing apparatus, accessory apparatus, and control method therefor with changing signal level of communication channel from one level to another
The image-capturing apparatus communicates with an accessory apparatus using a clock/communication request channel and first and second data communication channels. The camera controller switches its communication method between a first communication method in which data communication is performed while a clock signal is alternately switched between first and second levels and a second communication method in which data communication is performed in response to a communication request from the camera controller to the accessory apparatus, which is output by switching a signal level of the clock/communication request channel from the first level to the second level. The camera controller, in response to detecting a communication error in the first and second communication methods, transmits to the accessory apparatus through the second data communication channel a specific signal for restoring the communication while keeping the signal level of the clock/communication request channel at the first level.
1. An image-capturing apparatus to which an accessory apparatus is attachable, the image-capturing apparatus comprising:
a first communication channel, a second communication channel, and a third communication channel, each of these channels used for communicating with the accessory apparatus;
one or more processors; and
a memory storing instructions which, when executed by the one or more processors, cause the image-capturing apparatus to function as: a camera control unit configured to communicate with the accessory apparatus by a first communication method in which the camera control unit transmits camera data via the first communication channel in correspondence with transmission of a clock signal via the second communication channel, or by a second communication method in which the camera control unit transmits camera data in correspondence with reception, via the third communication channel, of accessory data, the accessory data having been received at a corresponding timing with respect to a change of signal level of the second communication channel from a first level to a second level,
wherein, when a signal level of the first communication channel is kept at a predetermined level for a predetermined time while a signal level of the second communication channel is kept at the first level, the camera control unit changes, after elapse of the predetermined time, a signal level of the first communication channel from the predetermined level to a signal level different from the predetermined level, and transmits first camera data via the second communication channel in the first communication method.
2. An image-capturing apparatus according to claim 1 , wherein the camera control unit controls a transition of communication mode from the second communication method to the first communication method after elapse of the predetermined time.
3. An image-capturing apparatus according to claim 1 , wherein the first camera data corresponds to a request for communication by the first communication method.
4. An image-capturing apparatus according to claim 1 , wherein the camera control unit, in response to detecting a communication error in a communication in the second communication method, keeps a signal level of the first communication channel at a predetermined level for a predetermined time while keeping a signal level of the second communication channel at the first level.
5. An image-capturing apparatus according to claim 4 , wherein the camera control unit detects, in the second communication method, the communication error based on at least one of parity information or a stop bit included in the accessory data received via the third communication channel.
6. An accessory apparatus attachable to an image-capturing apparatus, the accessory apparatus comprising:
a first communication channel, a second communication channel, and a third communication channel, each of these channels used for communicating with the image-capturing apparatus;
one or more processors; and
a memory storing instructions which, when executed by the one or more processors, cause the image-capturing apparatus to function as: an accessory control unit configured to communicate with the image-capturing apparatus by a first communication method in which the accessory control unit transmits accessory data via the third communication channel in correspondence with reception of a clock signal via the second communication channel, or by a second communication method in which the accessory control unit transmits accessory data in correspondence with change of signal level of the second communication channel from a first level to a second level,
wherein, when a signal level of the first communication channel is kept at a predetermined level for a predetermined time while a signal level of the second communication channel is kept at the first level, the accessory control unit transmits, after elapse of the predetermined time, in correspondence with change of signal level of the second communication channel from the first level to the second level, first accessory data via the third communication channel.
7. An accessory apparatus according to claim 6 , wherein the accessory control unit performs a reset operation of the communication by clearing the accessory data buffered for transmission to the image-capturing apparatus via the third communication channel, before reception of camera data via the first communication channel.
8. An accessory apparatus according to claim 6 , wherein the accessory control unit transmits, in response to reception of request via the first communication channel after elapse of the predetermined time and change of a signal level of the second communication channel from the first level to the second level, a response corresponding to confirmation of communication by the first communication method.
9. An accessory apparatus according to claim 6 , wherein the accessory control unit transmits, in the second communication method, the accessory data including at least one of parity information or a stop bit via the third communication channel.
10. An image-capturing system including an image-capturing apparatus and an accessory apparatus detachably attachable to the image-capturing apparatus, the system comprising:
a first communication channel, a second communication channel, and a third communication channel, each of these channels used for communicating with the accessory apparatus;
one or more processors; and
a memory storing instructions which, when executed by the one or more processors, cause the image-capturing apparatus to function as:
(1) a camera control unit configured to communicate with the accessory apparatus by a first communication method in which the camera control unit transmits camera data via the first communication channel in correspondence with transmission of a clock signal via the second communication channel, or by a second communication method in which the camera control unit transmits camera data in correspondence with reception, via the third communication channel, of accessory data, the accessory data having been received at a corresponding timing with respect to a change of signal level of the second communication channel from a first level to a second level; and
(2) an accessory control unit configured to communicate with the image-capturing apparatus by a first communication method in which the accessory control unit transmits accessory data via the third communication channel in correspondence with reception of a clock signal via the second communication channel, or by a second communication method in which the accessory control unit transmits accessory data in correspondence with change of signal level of the second communication channel from a first level to a second level,
wherein when a signal level of the first communication channel is kept at a predetermined level for a predetermined time while a signal level of the second communication channel is kept at the first level, the camera control unit changes, after elapse of the predetermined time, a signal level of the first communication channel from the predetermined level to a signal level different from the predetermined level, and transmits first camera data via the second communication channel in the first communication method, and
wherein when a signal level of the first communication channel is kept at a predetermined level for a predetermined time while a signal level of the second communication channel is kept at the first level, the accessory control unit transmits, after elapse of the predetermined time, in correspondence with change of signal level of the second communication channel from the first level to the second level, first accessory data via the third communication channel.
11. A control method of an image-capturing apparatus to which an accessory apparatus is attachable, the image-capturing apparatus including a first communication channel, a second communication channel, and a third communication channel, each of these channels used for communicating with the accessory apparatus, the control method comprising the steps of:
causing the image-capturing apparatus to communicate with the accessory apparatus by a first communication method in which the image-capturing apparatus transmits camera data via the first communication channel in correspondence with transmission of a clock signal via the second communication channel, or by a second communication method in which the image-capturing apparatus transmits camera data in correspondence with reception, via the third communication channel, of accessory data, the accessory data having been received at a corresponding timing with respect to a change of signal level of the second communication channel from a first level to a second level; and
causing the image-capturing apparatus to, when a signal level of the first communication channel is kept at a predetermined level for a predetermined time while a signal level of the second communication channel is kept at the first level, change, after elapse of the predetermined time, a signal level of the first communication channel from the predetermined level to a signal level different from the predetermined level, and transmit first camera data via the second communication channel in the first communication method.
12. A control method of an accessory apparatus attachable to an image-capturing apparatus, the accessory apparatus including a first communication channel, a second communication channel, and a third communication channel, each of these channels used for communicating with the image-capturing apparatus, the control method comprising the steps of:
causing the accessory apparatus to communicate with the image-capturing apparatus by a first communication method in which the accessory apparatus transmits accessory data via the third communication channel in correspondence with reception of a clock signal via the second communication channel, or by a second communication method in which the accessory apparatus transmits accessory data in correspondence with change of signal level of the second communication channel from a first level to a second level; and
causing the accessory apparatus, when a signal level of the first communication channel is kept at a predetermined level for a predetermined time while a signal level of the second communication channel is kept at the first level, to transmit, after elapse of the predetermined time, in correspondence with change of a signal level of the second communication channel from the first level to the second level, first accessory data via the third communication channel.
13. An image capturing apparatus according to claim 1 , wherein in the first communication method, the camera control unit transmits camera data via the first communication channel and receives accessory data via the third communication channel in correspondence with transmission of a clock signal via the second communication channel.
14. An image capturing apparatus according to claim 1 , wherein in the second communication method in which the camera control unit transmits camera data via the first communication channel in correspondence with reception of accessory data via the third communication channel, the accessory data is received at a corresponding timing with a change of signal level of the second communication channel from a first level to a second level.
15. An image capturing apparatus according to claim 1 , wherein the clock signal is a signal where change of a signal level of the second communication channel from the first level back to the first level via the second level is repeated 8 times.
16. An image capturing apparatus according to claim 15 , wherein the predetermined time is longer than a time when a change of a signal level of the second communication channel from the first level back to the first level via the second level is repeated 8 times.
17. An accessory apparatus according to claim 6 , wherein in the first communication method the accessory control unit transmits accessory data via the third communication channel and receives camera data via the first communication channel in correspondence with reception of a clock signal via the second communication channel.
18. An accessory apparatus according to claim 6 , wherein in the second communication method the accessory control unit transmits accessory data via the third communication channel in correspondence with change of signal level of the first communication channel from a first level to a second level and receives camera data via the first communication channel in correspondence with transmission of the accessory data via the third communication channel.
19. An accessory apparatus according to claim 6 , wherein the clock signal is a signal where a change of a signal level of the second communication channel from the first level back to the first level via the second level is repeated 8 times.
20. An accessory apparatus according to claim 19 , wherein the predetermined time is longer than a time when a change of a signal level of the second communication channel from the first level back to the first level via the second level is repeated 8 times.