DB101 UART

Go To Last Post
6 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Does anyone understand the UART connections on the DB101 board? There are 4 connections besides ground. RXH, TXH, RXL and TXL. So which ones do I use?

Atmel's doc8073.pdf "AVR481: DB101 Hardware User's Guide" contains this paragraph:

The level converted RxD and TxD lines are available on the header – the pins are marked with silkscreen labels RXL and TXL. The RS232 converted RxD and TxD signals are available on the same header, where the pins are marked with silkscreen labels RXH and TXH.

I suppose that would make it clear if I could speak Atmelese. :)

I also have the schematic, ATDB101_schematic_refE.pdf. but that makes me even more confused. Besides the level conversion stuff it has a chip described as "SPDT analog switch or 2:1 multiplexer" and a signal coming from the Atmega called RS-232_SEL. Is Rube Goldberg alive and well and living in Norway? :)

Supposedly this thing comes with a UART software module and a joystick menu to configure it. So if I could just figure out where to connect the wires from my PC I might be in business.

P.S. I just noticed something else. The joystick can't interrupt the AVR. It must be polled. The Butterfly does it better.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I just hooked up the RXH to receive from the PC to test the terminal program( had to reload the newer version since I received one of the non backlight ones that were offered awhile back). The RXL and TXL are at logic level and the RXH and TXH are set for rs232 levels. Yes I went thru the same agony and it can be found but do not remember at this time. I made a simple carrier board and the RS232 was the first thing I hooked up.

Pete

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

It seems to me that part of the complications is that there is an option to select between RS232 or TTL I/O for the serial communications. To be sure though, I'd have to go back and refresh with the code and schematics. I just can't remember clearly as, it was several months ago that I spent any time with the DB101 stuff.

Maybe someone else has a better memory.

You can avoid reality, for a while.  But you can't avoid the consequences of reality! - C.W. Livingston

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

digitool wrote:
I just hooked up the RXH to receive from the PC to test the terminal program( had to reload the newer version since I received one of the non backlight ones that were offered awhile back). Pete

Thanks guys. I was leaning towards the RXH stuff. So what did you reload, and where did you find it?

I also have the non backlight version.

EDIT:: Never mind the question about the reload. I will probably use the GCC port from Martin Thomas.

Steve

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

In a nutshell: the *XH pins are the ones which run at normal RS-232 levels, suitable for direct connection to a computer's serial port or similar. The *XL pins are the logic level versions, which run at normal logic levels (sutable for direct connection to another AVR, for example).

- Dean :twisted:

Make Atmel Studio better with my free extensions. Open source and feedback welcome!

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I'm trying to hook my DB101 up to a 1.8V mainboard, starting with the UART. I'm using the GCC version 20080301 (latest) of the firmware, compiled on Ubuntu 8.04 (avr-gcc 4.2.2, avr-libc 1.4.7) ... no luck so far.

Electrical: hooked up 5V to VREG, 1.8V to VEXT, using RXL/TXL. Told the DB101 to use logic levels, 2400-8-N-1 (and 115200 baud too). "date > /dev/ttyS1" (from the mainboard) produces no output whatever on the DB101 display. I even double checked by switching pins on the mainboard, in case RXL shouldn't hook up to TX (and vice versa). Same "nothing displays" failure mode...

But no luck. Can anyone share a success story using the DB101 with 1.8V signal levels? Any advice, hints, things to check to make sure the DB101 is behaving? I'll try to hook it up to a 3.3V board too. Using RS232 levels instead of logic levels is even doable -- but painful, since I have virtually no RS232 ports.