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RGB LED Coffee Table Question

Aaron Attar
Intellectual 265 points

In the project posted here:
http://e2e.ti.com/group/msp430launchpad/m/project/447779.aspx

They mention "the screen is updated and the table data is sent out the USB port to a FTDI USB-to-Serial Adaptor which talks to the MSP430 over UART". They show their entire schematic and all their code is freely available.

My question is why was the FTDI USB-to-Serial Adaptor needed when the Launchpad provides a USB Serial COM emulation?

any ideas or thoughts would be greatly appreciated!

  • 0
    Genius 4925 points

    I think they need it because they are working with a 500k bit/s communication which is very fast for a UART interface and if I remember correctly someone mentioned that the launchpad UART handles 9600 or 57,6k at most. So it's basically to slow.

  • 0 in reply to Bernhard Weller
    Intellectual 265 points

    I don't even see the FTDI in the project pictures of the board that they posted.

    Also, why is a baud of 9600 too slow? ... I don't understand how you know how fast a baud you need?

    thanks

  • 0
    Guru 35605 points

    Aaron Attar said:
    the Launchpad provides a USB Serial COM emulation

    Does it?

    Are you sure that isn't just an "emulattion" (sic) interface...? 

  • 0 in reply to Andy Neil
    Intellectual 265 points

    Andy Neil:

    Yes. Page 6

    5861.LaunchPad_User_Guide.pdf

    Bernhard Weller:

    Ok, so I did some digging and I see now where and why they got the baud rate that they did. I can't however find the FTDI on the schematic they provided. Do you know where or how to connect the FTDI to the launchpad?

    4186.schematics.zip

  • 0 in reply to Aaron Attar
    Intellectual 265 points

    After doing some searching on the internets.... I did manage to find an example of an FTDI attached to an MSP430.

    https://www.youtube.com/watch?v=Aghqujx7ViA

    from the image in the video, it seems that all I need to do is connect it to the Tx (P1.1) and Rx (P1.2) of the launchpad.

    Does that sound right to yall?

  • 0 in reply to Aaron Attar
    Genius 4925 points

    I've also looked through the schematics and couldn't find it either. I know from the Silicon Labs UART to USB chips, that they only have to be connected to the TX and RX pin, just as if it was a normal UART connection. From the datasheet of one of the FTDI chips it looked like being the same.

    Just do be careful about your voltages, as USB provides 5 volts and your MSP runs with 3 volts. From a short view of the datasheet of one of the FTDI chips, it looked like it provided a voltage input to set the I/O voltages, so you can apply 3 volts there and it should be fine.

  • 0 in reply to Bernhard Weller
    Intellectual 265 points

    Hmm.... I was finally able to get into contact with a dev from that project.... I'll post here his answers once he replies.

    thanks for the effort Bernhard, I really appreciate it :) 

  • 0 in reply to Aaron Attar
    Intellectual 265 points

    Aaron Attar  -  max, i have a question about yalls project. why did yall use the ftdi-usb board for uart when the launchpad has a usb com emulation that can be used for uart?  thanks

    Nov 10, 2011   

     

    Max Thrun  -  @aaron. Because the speed of the usb->uart on the launchpad is limited to 9600 baud. The table takes 8*16*3*8=3072 bits for a full frame so at 9600bps we would have have a refresh rate of only 3FPS. With the ftdi chip we were using 500KBaud giving us >160FPS.

    Nov 11, 2011   

     

    Aaron Attar  -  hmm i see.... i don't see the ftdi chip on the schematic.... did you simply attach it to the Tx (P1.1) and Rx (P1.2)? your design of cycling through the rgb color layers really helped me on my final project and i'm just trying to better understand exactly what it was that yall did.

    Nov 11, 2011  

     

    Max Thrun  -  yeah it is just attached to the TX RX headers on the launchpad. I was initially going to put a header on the main board so that the ftdi module from sparkfun could plug right into that but I forgot to add that before ordering the board so it is just attached with some ribbon cable. I'm glad our project helped you with yours!

    Nov 11, 2011   

     

    Aaron Attar  -  ok great... so just to double check... yall attached it to 1 and not 2 ( http://dl.dropbox.com/u/21163284/CIMG3790.JPG ) ...also ...last question (i hope) .. i don't understand why or what the part labeled as RF2500 is used for or why it's needed? i'm trying to map out the best way to wire ours... we have 18 of these LED drivers in series... and its a lot of wiring! its such a hard trade off.... organized (longer wires) vs craziness (less noise)

    Nov 12, 2011

     

    Max Thrun  -  1 and 2 are attached to each other. I removed the jumpers on 2 (disconnecting the uart on the msp430 from the programmer) and attached a female header from the ftdi to the RX line (actually i think the rx and tx might have been label wrong) the RF2500 is on there because i originally was going to make the table wireless, but time didn't permit this.the rf2500 board was going to talk to the launchpad over SPI

    here is a link to the rf2500 dev kit

    http://www.ti.com/tool/ez430-rf2500

    18 driver chips!! Definitely post some pictures of your build.

    Yesterday 3:15 AM   

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