Arduino Forum

Using Arduino => LEDs and Multiplexing => Topic started by: acid on Nov 30, 2012, 09:07 pm

Title: How to connect LEDs to RX0/TX1 and still be able to flash?
Post by: acid on Nov 30, 2012, 09:07 pm
I've tried to connect 2 leds on Digital Pin0 and Digital Pin1. I know it's connected to UART RX/TX. After this connection I wasn't able to flash device - no response.
But there must be some way to isolate this LEDs from RX/TX pins during programming(except putting release buttons).

So I want to have LEDs on those pins (using all pins on Arduino UNO) and be able to program board.
Title: Re: How to connect LEDs to RX0/TX1 and still be able to flash?
Post by: John_Smith on Nov 30, 2012, 09:19 pm
What have you got connected to all the other pins ?   more leds?
Title: Re: How to connect LEDs to RX0/TX1 and still be able to flash?
Post by: Grumpy_Mike on Nov 30, 2012, 09:20 pm
The best way is to switch them out. That is physically disconnect them.

Alternatively you can use a buffer or a transistor to isolate them from the serial signals. They will then flash as you upload stuff but when the sketch starts running they will be fully controllable.
Title: Re: How to connect LEDs to RX0/TX1 and still be able to flash?
Post by: acid on Nov 30, 2012, 09:21 pm
Other LEDs, SPI. The number of pins are exactly matches to requirements if I only can isolate them and use flash device without disconnecting LEDs.
Title: Re: How to connect LEDs to RX0/TX1 and still be able to flash?
Post by: acid on Nov 30, 2012, 09:22 pm

Other LEDs, SPI. The number of pins are exactly matches to requirements if I only can isolate them and use flash device without disconnecting LEDs.


Could you please give me some reference values of elements?
Title: Re: How to connect LEDs to RX0/TX1 and still be able to flash?
Post by: John_Smith on Nov 30, 2012, 09:39 pm
You can drive loads of LEDs from 3 pins with a shift register ....
Title: Re: How to connect LEDs to RX0/TX1 and still be able to flash?
Post by: Grumpy_Mike on Dec 01, 2012, 12:12 am

Other LEDs, SPI. The number of pins are exactly matches to requirements if I only can isolate them and use flash device without disconnecting LEDs.


You can't without isolating the LEDs from the serial input. As I said before you fdo this either electrically or mechanically.