UART Connection

15 1659
Edited by Tido at Feb 21, 2016 20:01

Hi,

I couldnt figure out how to interface a serial device to Guitar's uart pins Tx, Rx, 8th and 10th pins in 40 pin header. Can anyone tell me how to use it in android or guide me where i can find information? Also are the uart pins ttl output or cmos output? and works with 3.3v or 5v? Since the device i need to connect is 3.3v cmos i need to use logic level converter.

Thanks
12458  

Yes, i have read everything that i could find but thats about debug com port connection to pc. Nothing about uart connection between guitar and a microcontroller. For example how to access uart in an android application? all i can find is about i2c and spi in linux. There is a wiki page about using java but its about using gpios not uart. Do you have any idea about uart in android?

Noone knows how to use uart pins on android?

Tido  
Edited by Tido at Feb 21, 2016 20:15
osmanates replied at Feb 21, 2016 11:56
UART pins on android?  3.3V or 5V?

Hi,

I don't know about the difference between ANDROID and Linux, I only use Linux (Lemuntu).

There is a user manual and in chapter 8 it says:

There are 40pins for GPIO on LeMaker Guitar Base Board Rev. B,
including TWI, PWM, SPI, I2C, UART, etc....
Via the basic way, you can control the digital ports input or output from the sys user space.

About the voltage I have no clue, did you search the forum?

Can you say what you want to read out from the UART, logging the boot process?




Hi,
I figured out that voltage is 5v. so anyone needs an uart connection to a microcontroller or device which works with 3.3v or some other than 5v need to use logic level converter.

I need to use uart to communicate with a rf module under android. I made some progress but now need a serial terminal like minicom on android. Just found microcom but didnt work that much. I'm open to suggestions.

osmanates replied at Feb 21, 2016 14:18
Hi,
I figured out that voltage is 5v. so anyone needs an uart connection to a microcontroller or dev ...

Just to update i have made some progress. First i tried microcom serial terminal bundled with busybox but it didnt work much so later i tried to port picocom from linux to android and it worked. So i can now say that guitar can communicate with the uart device on android via its 8th nad 10th pins on the 40 pins header. I had to use some kind of logic level converter since guitar uses 5v and my rf module uses 3.3v.

finger  
Edited by finger at Feb 22, 2016 17:22
osmanates replied at Feb 22, 2016 13:32
Just to update i have made some progress. First i tried microcom serial terminal bundled with busyb ...

That is really weird, usually the uart is 3.3v (TTL).
I measured TX and GND and got 3.3v. RX and GND and got 3.3v.
I am about to interface a device that is 3.3v and not 5v tolerant, can you please double check how you figured out the uart is 5v?

Can someone from LeMaker confirm the uart ttl level?

12458  
osmanates replied at Feb 22, 2016 04:18
Hi,
I figured out that voltage is 5v. so anyone needs an uart connection to a microcontroller or dev ...

Hi there you got it all wrong. Most ARM processes operate at either 3.3v or 1.8v. The Guitar most likely is at 3.3v Logic level as from the datasheet it say the I/O core ia powered by 3.3v

12458  
Edited by 12458 at Feb 23, 2016 20:55
osmanates replied at Feb 23, 2016 03:32
Just to update i have made some progress. First i tried microcom serial terminal bundled with busyb ...

First all the logic level is 3.3v. Secondly you could a voltage divider instead of a logic level converter(here refering to you saying that for whatever reason the guitar is 5v logic level)

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