HarryFilm said:
CafferyPhoto said:
jolyonralph said:
this patent is just about communication protocols
What protocols do the other companies (Sony, Nikon) use?
From an electrical point of view I am assuming a 2-bit, 3-bit or 4-bit parallel protocol much like the old-time Centronics printer ports but with less pins! In this case I suspect depending upon the number of pins on various mounts that Canon uses 2 data pin + 2 ground pins, or 3 data pins and 3 ground, or 4-pins for data and 4 pins for ground.
It could also be a serial protocol such as RS-232 or RS-422 like they used on old-style video cameras and editing decks. In terms of speed the Baud rate (in bits per second) Canon should be able to get between 56k/baud up to 384k/baud and depending upon the error correction protocol used which needs extra bits, it could be between 6000 bytes per second up to 48,000 bytes per second which is PLENTY to get and set various lens parameters at up to 120 frames per second! This means it would be CHEAP to produce (less than $3 per lens) because if they tried doing a micro-USB style serial communications system at MANY megabytes per second, it would cost between $10 to $150 extra per lens depending upon the lens parameters needed to be get/set and powered!
I think I have read that camera-lens-data exchange runs via I2C (maybe not Canon) and - I checked the following link:
https://photo.stackexchange.com/questions/61959/does-anyone-have-any-information-on-canons-vl-mount-regarding-pinout-and-protoc
Where the following contact scheme is provided:
Contact shape / Function
Dot / Battery voltage - supply for all actors
Bar shaped / Analog ground (minus) for actors like motors
------------------------------------------------------------------
Dot / Digital supply voltage
Dot / Digital data signal out from Camera to Lens
Dot / Digital data signal in from Lens to Camera
Dot / Digital clock signal to "align" the bits for both information channels
Dot / Digital ground (minus)
Which seems a well done arrangement for a mixed digital / analog system.
So it's definitely not RS-232/-485 (no common clock) nor I2C (only one data wire). If it is SPI (a synchronous serial interface using a common clock) they have no chip select (selection of a device) lines, maybe they use the cpu in the lens to interpret commands and send the info to the correct subdevices in the lens for e.g. focusing and electr(on)ic aperture.
Maybe Canon prepares to use I2C which needs one contact less. I2C is a wide spread communication protocol for sensors, displays and some actors. I2C uses address based bus devices (very flexible), allows more than one controler on the bus and can reach data transmission speeds up to
>>>>>
– Standard-mode (Sm), with a bit rate up to 100 kbit/s [~10 kByte / s]
– Fast-mode (Fm), with a bit rate up to 400 kbit/s [~40 kByte / s]
– Fast-mode Plus (Fm+), with a bit rate up to 1 Mbit/s [~100 kByte / s]
– High-speed mode (Hs-mode), with a bit rate up to 3.4 Mbit/s. [~340 kByte / s]
<<<<<< from https://www.i2c-bus.org/specification/
A 100 Hz readout of an acceleration sensor wired up by I2C with an Arduino Nano and transfer to a Serial line via USB is no problem for me as a medium experienced former programmer - what if well experienced programmers use I2C and optimize it in a well designed environment?
And what for? Who knows but a lens using at least 3 linear drives (with 3 independent motors) for focusing could adjust lens group tilt by itself (via DPAF) or do some tilt to extend the content which is in focus. This would at least triple the amount of data for the focusing operation.