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how does chdk communicate with usb?

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how does chdk communicate with usb?
« on: 30 / June / 2016, 10:43:50 »
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Hi there,

I've been trying to understand the working theory of CHDK for sometime. My question is how does CHDK receive/send the data from/to USB? I used to work with FPGA/microcontroller + USB + PC. Say if I send data from PC to FPGA, then software on PC detects the USB device and write functions through USB, when data arrived in FPGA which connects to the USB controller on the other side, the firmware inside FPGA will deal with the data received, and according to the functions in the firmware do certain operations. In the camera case, the CHDK is like the firmware to deal with the data received, then my question is if there's any specific file in CHDK that deals with the communication work?
Any hints will be appreciated!

Elaine

Re: how does chdk communicate with usb?
« Reply #1 on: 30 / June / 2016, 11:42:05 »
CHDK extends the PTP interface built into every Canon P&S camera. 

 See : Wikipedia : Picture Taking Protocol

Details on how this works can be found here : CHDK Wikia : PTP Extension

If you want to experiment a bit,  CHDK's Lua scripting language provides a convenient method of communicating between your PC and the camera :  Lua : PTP Scripting
Ported :   A1200    SD940   G10    Powershot N    G16

 

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