UART not Working through CD74HC4052E

Matthew Baker

I am trying to communicate with 2 sensors that operate at a baud of 9600. The sensors operate on 5V logic and so does the Arduino Mega I am using. The sensors are connected to the appropriate power and the logic controls for the multiplexer are set-up and functional. Below is the pins that are connected.

An: Arduino Tx

Bn: Arduino Rx

A0 and A3: Sensor Rx

B0 and B3: Sensor Tx

Vcc: 5V

Vee: 0V

The information returned to the Arduino should be plain ASCII text (ex Z 00123). Instead I am getting stuff like this:

5.þ+
úÂNþ
Êþ Ã‚ŠÊüÿ1þ0ü üÿùþþŠÿò
ª
úþ¢ÿ
ü%ðøøÿ.
ŠÊÊÀþ01ù0ñð‚‚
�‚.1à
5.ñú2
2ð
¢ùò

The same sensors work when directly connected to the Tx and Rx on the Arduino with the same commands being sent to them. The only difference is the multiplexer chip. Is there something wrong with my set-up and can the multiplexer be used in this situation?

over 9 years ago

0 Clemens Ladisch over 9 years ago

Guru 316440 points

I'd ask for the schematic, but I guess you don't have one.

You did not mention any decoupling capacitors.

Show your code.

0 Matthew Baker over 9 years ago in reply to Clemens Ladisch

Prodigy 50 points

The circuit schematic is below.

The code is attached. multExampleCode.zip

0 Clemens Ladisch over 9 years ago in reply to Matthew Baker

Guru 316440 points

That is not a circuit diagram.

In C strings, the escape character is not / but \.

0 Matthew Baker over 9 years ago in reply to Clemens Ladisch

Prodigy 50 points

I didn't notice the errors in the code and have now fixed them. The circuit schematic can be seen below except I am using an Arduino Mega.

I also tested my code with the revisions with the Rx and Tx lines connected right from the sensor to the Arduino bypassing the multiplexer and the sensor was able to be read. When I tried the same code with the sensors connected through the multiplexer the sensors can no longer recognize the commands and they give back an error message.

0 Clemens Ladisch over 9 years ago in reply to Matthew Baker

Guru 316440 points

I do not see a decoupling capacitor.

Please show the datasheet of the sensors.

0 Matthew Baker over 9 years ago in reply to Clemens Ladisch

Prodigy 50 points

I rebuilt the circuit using de-coupling capacitor between Vcc and Ground and was able to read the 2 senors. I then added the last of my 2 sensors and was able to read everything. There must have been a bad connection or issues with the chip without the decoupling capacitor.

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UART not Working through CD74HC4052E