| ??? 03/09/08 18:49 Read: times |
#152047 - Further Explanation Responding to: ???'s previous message |
Mehdi said:
Indeed your answer made me more aware about the subject,
Michael said:
The fast analogue output requirement out of a scanner CCD device often requires some clever design to deal with the fast data flow rate. In this Sony chip at 1MHz clocking with 3x 5300 pixels to capture at say 8-bits per pixel there will be just under 16K bytes of data to manage for each scan time which is on the order of somewhere between 5 and 6 milliseconds (assuming the 1MHz clock rate the chip specs are referenced to). Can you tell me please 5 and 6 milliseconds come from where? For an 8052 design it may be well to use a derivative part that can support a external RAM array. 5300 Pixels @ 1 usec per pixel = 5.3 milliseconds. Mehdi said:
Why RAM is needed while i must send real time data to pc?
Michael said:
A smallish CPLD or FPGA could be used to create the clocks to run the CCD array, the video decoder/graphics digitizer and digital data DMA process into the RAM. The CPLD could, if enough pins and logic cells are allocated, If you are running in single scan mode you will need RAM to buffer one scan because the 8052 itself does not have sufficient RAM itself and probably cannot gather the data fast enough to put it into a RAM directly. Additionally only the very fastest modern interfaces to the PC are fast enough to even consider moving the pixel data into the PC at or above the scan rate. This the RAM is needed to be used as the elastic store between the CCD clock rate and the PC transfer rate. Mehdi said:
Did you meen all ADC Interfacing,CCD Clocking,Sending Data to pc can be done by a Spartan 2 Xilinx FPGA like XC2S150?
No I was proposing that the 8052 would still be involved because at the time it was not clear at all to me that you were sending all the data directly to the PC. However you may want to have your MCU do whatever dark level compensation of the pixels before sending them to the PC. Note that if you were to implement the 1 MHz clocking of the CCD the net serial transfer rate to send three 8 bit digital pixel samples per clock is 8*3*1MHz = 24 MHz in raw bit rate without any protocol overhead involved. To get this into a PC in real time without an elastic store memory would require you to use the variety of USB 2.0 that operates in the 480Mbit mode. Not many USB microcontrollers support this rate. Michael Karas |
| Topic | Author | Date |
| CCD linear sensor | 01/01/70 00:00 | |
| Link? | 01/01/70 00:00 | |
| CCD | 01/01/70 00:00 | |
| RTFDS | 01/01/70 00:00 | |
| You've got to read the datasheet | 01/01/70 00:00 | |
| Some hints | 01/01/70 00:00 | |
| Thanks Kai,Richard,Andy And Steve | 01/01/70 00:00 | |
| Fast A/D Converter | 01/01/70 00:00 | |
| Thanks Michael, | 01/01/70 00:00 | |
| Further Explanation | 01/01/70 00:00 | |
| More Advice? | 01/01/70 00:00 | |
| I would not consider parallel port. | 01/01/70 00:00 | |
| Windows is probably a poor choice of platforms | 01/01/70 00:00 | |
Enhanced Parallel port on ISA does 2 MBps | 01/01/70 00:00 | |
| frame grabber | 01/01/70 00:00 | |
| Richard And Michael | 01/01/70 00:00 |