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+spt to hex converter
+
+This programm extract firmware from hex2spt gerenated Cypress EZ-USB
+spt script file.
+Copyright (C) 2013  Emmanuel Fusté
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+spt is a generic USB commands scripting format, but as we know how hex files
+are converted to spt by standard cypress tools or procedures to get back
+an hex file from a hex-converted-to-spt file.
+
+
+each USB transaction is described by a record
+record format: 32 byte header in little endian + data
+ 
+uint Signature == 0x54505343 or byte[4] == 'CSPT' //4 
+uint RecordSize == header size + data size == 32 + data size //8
+ushort HeaderSize == 32  == 0x0020//10
+byte Tag == 0 == 0x00//11
+
+Device on wich the script will be played : selected at runtime,
+0x0 in the script:
+byte ConfigNum == 0 == 0x00 //12
+byte IntfcNum == 0 == 0x00 //13
+byte AltIntfc == 0 == 0x00 //14
+byte EndPtAddr == 0 = 0x00 //15
+
+byte bReqType == 0x40 in our case (TGT_DEVICE|REQ_VENDOR|DIR_TO_DEVICE) //16
+byte CtlReqCode //17
+byte reserved0 is generaly 0x20//18 
+
+ushort wValue //20
+ushort wIndex //22
+byte reserved1 ~ 0x9F //23 
+byte reserved2 ~ 0x00 //24
+
+uint Timeout ~ 0x00000005 //28
+uint DataLen; //32
+
+hex to spt converter do the following:
+1 CPU put in reset mode (A0 request to write 0x01 at 0xE600 for FX2LP)
+2 upload of vendor_ax firmware with A0 request
+3 CPU put in run mode (A0 request to write 0x00 to addresss 0xE600 for FX2LP)
+4 upload of external RAM code with A3 vendor request implemented by vendor_ax
+5 CPU put in reset mode
+6 upload of RAM code with A0 vendor request (all code under 16k on FX2LP)
+7 CPU put in run mode
+
+spt generated by cypress tools upload inconditionnaly vendor_ax firmware.
+If there is nothing to upload to external ram, step 4 is skipped.
+
+If manualy recorded, step 2,3,4,5 could be omitted if no code need to be 
+uploaded to external ram.
+
+all contiguous hex record data are packed in one usb transaction and re-split
+in two if the packed result in payload > 4k
+Cypress tools generate hex file with 16 bytes of data max per record.
+Decoded spt data payload will be re-split in 16 bytes hex record.