Since I am the one who started this topic - sorry for not following it up (health reasons, I do not read or post anywhere anymore) .
Hello to Leo and all. I still use the Linduino that LT kindly gave me. It is a very good board with USB ground isolation and clean power, and has excellent free code. I also use the clone that I built myself (see earlier posts and video).
I am a bit sorry that Linduino has not taken off in the Arduino world, but as LT has stated: They do not want to set a price that competes with Arduino and clones. Fair enough. LT is not a sandbox player but a professional business.
Du to reasons stated above, I have had little chance to work with electronics. However, if anyone wants to make a Linduino clone from an Arduino, it is quite easily done. But you must read my earlier posts about MULTIPLEXING OF I2C AND SPI.
On page 11, Block Diagram in
http://cds.linear.com/docs/en/demo-board-manual/DC2026AFB.PDF you will see that there is a multiplexer. You will have to reproduce this MUX or it's function. On page 14 you will see the schematic with the Atmega processor U7 and the MUX chip U4. This is the MUX you will have to buy, or emulate its switching by using junk box logic (as I have written in earlier posts). You can mount the MUX and the other components around it on an empty Arduino shield.
Now look at the schematic
http://cds.linear.com/image/resized/934asch.jpg from
http://www.linear.com/solutions/3305.
You will see that the board has an a DAC, an ADC, a MUX and an EEPROM.
The WIRED Arduino I2C is OCCUPIED by the EEPROM. The DAC and ADC shares Arduino SPI via the MUX. The resultant signal is DEMULIPLEXED in the earlier mentioned Linduino MUX. So there are two MUXes - one for mixing the signals on the DAC/ADC board, and one for separating them before they reach the Atmega on the Linduino board.
So, unless you understand what I have just said, you will in my opinion find it difficult to use an Arduino as a Linduino clone.
OK. That's it. I am sorry I cannot follow this up. I highly recommend the Linduino and the code Library, and hope more people will use it. Thanks again to LT for generous help.