What the heck does the TTL cable do? Forgive my not knowing

Sorry folks I am so new to electronics, specing and building them that I have to ask the dumb questions. What is the USB-TTL cable for on Gen 3 Electronics? Can't I just dump my G-code on an SD and walk away do I still need a direct link to a computer?

From reading only, I've seen a few projects that need to be paused at some point and a captive nut inserted.

Anyone else?

The SD card is not really working yet in the firmware. The design still needs some kind of display and control pannel to make that possible.

So yeah it is still a required item and I would think would still be useful down the road also.

freds Wrote:
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> The SD card is not really working yet in the
> firmware. The design still needs some kind of
> display and control pannel to make that possible.
>
> So yeah it is still a required item and I would
> think would still be useful down the road also.


Yep doing some more reading up I see I need to get one. Another order into Makerbot for me. Thanks for the heads up.

Sorry if this seems like another dumb question, but what is the difference between the TTL cable and the bootloader?

Does the bootloader only need to be used once?

Thanks in advance.

The bootloader is a program that is first in control when you reset the processor or it gets reset automatically by the RTS signal that is one of the signal lines from the TTL cable (depends on a jumper on the board).

It has first dibs on the serial port to receive a new program to load into the flash memory of the chip.

There is a time window in which if it starts to receive a new program via the serial port that it will re-flash the program memory with. When it times out the boot loader will then start executing the last sucessfully loaded program.

Note the chip can wear out; depending on the version it can be reprogrammed >- 1000 times.

So are you saying that only the TTL cable is necessary for programming the sanguino/arduino?

If that is the case, why does the documentation for Motherboard and Extruder controller refer to this? --> [www.ladyada.net]

Thanks a lot again.

The USB to TTL serial cable is like a USB to RS232 serial cable except it uses the 0 and 5 volt logic levels of Transistor Transistor Logic (TTL) chips rather than the -12 and +12 volt logic levels of RS232.

You need the cable to communicate with the bootloader in an Arduino or similar microcomputer. That's how you load a program into the Arduino.

You need a DIFFERENT device to program the Arduino bootloader into a bare ATMega chip to make it into an Arduino. Usually you purchase and Arduino with the bootloader already programmed.

JohnWasser Wrote:
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>
> You need a DIFFERENT device to program the Arduino
> bootloader into a bare ATMega chip to make it into
> an Arduino. Usually you purchase and Arduino with
> the bootloader already programmed.

The device you pointed to is a iscp programmer. Bare AVR chips from the manufacture need to be programmed with a iscp or jtag programmer.

The bootloader enables you use a simple serial port, it does have a slight disavantage in that it takes 2K of the available memory and has to timeout after a reset before your program starts running.

If you use the 5v USB to TTL cable it can also function as a ISCP programmer with the right software and proceedures. Which I have documented in my blog here:

[exmrclean.blogspot.com]