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Wiring Hardware >> Tangible computing >> Does Serial1 TX have a pullup resistor?

Message started by roypardi on 04/16/09 at 20:34:39

Title: Does Serial1 TX have a pullup resistor?
Post by roypardi on 04/16/09 at 20:34:39
Hi - I am trying to use Serial1 on the Wiring board  to talk to two Gamoto motor controller boards. I have then wired in parallel as per their docs and I seem to be able to address both motors (they have a DIP switch to set board IDs) but I am getting some odd/bad data.

What I don't know is if I need the 10k pull up resistor they describe below. I tried it and it seemed to kill all communication - but maybe I hooked it up wrong. Before I assume I don't need it I thought I would ask here - does the TX line float when not in use?


This option is normally disabled.  It allows you to connect up to 8 Gamotos to the same
serial TX and RX lines, with no additional hardware other than a 10K pull-up resistor, which may be needed in some cases.  When this bit is set, the Gamoto allows the TX line to float when it's not being used.  Since each Gamoto only replies to messages addressed to it (by the correct header/DIP switch combination), then only the proper Gamoto will reply.  Since the TX line is floating when not in use, a 10K pull-up resistor is recommend, if not already included in your serial transceiver or MCU.

Title: Re: Does Serial1 TX have a pullup resistor?
Post by barragan on 04/17/09 at 17:14:04
the pull-up is not part of the board, but you can do it very easily with the 10k resistor going from the pin to +5V (VCC)
What sort of communication problems are you having? please use Wiring 0019 which fixes a bug related to Serial1.

Title: Re: Does Serial1 TX have a pullup resistor?
Post by roypardi on 04/24/09 at 00:42:19
Thanks for the reply - I've added the 10k pullup and life is good (at least with this project ;-) ) Not sure why it didn't work the first time I tried it.

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