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Topic: The 0.1uF capacitors when using FTDI programmer (Read 4158 times) previous topic - next topic


Great ! How about CTS? What's that ?

Not required in this application and can be left disconnected.



Feb 02, 2013, 03:11 am Last Edit: Feb 02, 2013, 03:14 am by retrolefty Reason: 1
If the PC com link was set-up with the 'hardware handshacking' enabled, the CTS (clear to send) would be how the device would tell the PC it was ready to receive data if any is waiting to be sent. The comm port as used by arduino (and most all PC serial applications) use the 'no handshake' option choice to run the link at. There is also a 'software handshake' option where the two sides of a comm link send the ascii Xon and Xoff control characters to tell the other side to stop or start sending data. That is also not used in most PC applications. But both options are available for interfacing with such thing a older modems and other data communication devices.



Great ! How about CTS? What's that ?

cts, dsr, ri, etc are inputs to the pc and therefor can never be used as arduino control bits.


But the timing has to be right, hold down the reset, select the program from the IDE, when it says loading, count one two three, and release the reset.

I have tried this ! It's really do work well ! But the timing really have to be correct. Have to release the RESET button once the IDE shows 'uploading..'

Thanks ! Finally I understand why is there a cap there- to bring the RESET High and LOW. :)

When I want to upload a new sketch, the we should RESET our microcontroller so that the previous sketch is deleted and pull the RESET HIGH to allow the new program to load into ?

Am I correct ?

Thanks !


Thanks ! Finally I understand why is there a cap there- to bring the RESET High and LOW.

Well actually that should read 'to bring the reset Low then High'.  ;)


Nick Gammon

Resetting the processor does not delete the old sketch.
Please post technical questions on the forum, not by personal message. Thanks!

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