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Thread: Help a newbie build a mini e-reader with lcd and micro SD card?

  1. #1
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    Help a newbie build a mini e-reader with lcd and micro SD card?

    Hi all,

    I am wanting to start a project to make an e-reader.

    It will comprise text files on an SD card which are then read and displayed onto an LCD screen plus the ability to scroll up-down (and/or left-right). I plan on using a DOGM204 lcd module and probably a teensy 3.1 (although other teensy models would be considered if you think they are more appropriate).

    I would really appreciate any help as to how I could make this.
    Last edited by RUSquared; 01-02-2014 at 08:36 PM.

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    Is this a student assignment?

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    Senior Member PaulStoffregen's Avatar
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    I recently tested Adafruit's 2.2 inch TFT, which is 320x240. It's really nice with Teensy 3.1. It also has the SD socket built in.

    Software-wise, this seems pretty simple. Read the files from the card, probably starting from an example which reads them and prints to the Arduino Serial Monitor. Then just add code to also print to the display. Adafruit's library uses Arduino's print class, so it accepts the same print stuff as Serial.

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    Hi stevench, no it's not a student assignment, although I am a student.

    Hi PaulStoffregen, I just checked out the display you mentioned - unfortunately it doesn't seem to be the best size for my project. I am wanting to display in an area about 60 x 22 mm (+- a couple of mm), and the DOGM204 is the only one I have found that is closest to those dimensions.

    I did stumble upon a post from earlier last year which you contributed to here which might be helpful to me.
    Questions I have though would still be: How do I modify the circuit to include an SD socket (something like this?, How do I power it via battery instead of USB?, and What are the pot and two buttons seen on the right hand side and the resistor on the lower left for?

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    Senior Member mortonkopf's Avatar
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    well, a couple of pointers:

    for how to set up the sd card with the Teensy read this guide for the basic connections: http://forum.pjrc.com/threads/16758-...-MicroSD-guide

    it might be most straight forward to go with a screen that has already got drivers and sketch code available, with lots of different examples.
    Last edited by mortonkopf; 01-03-2014 at 10:51 PM.

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    Quote Originally Posted by mortonkopf View Post
    well, a couple of pointers:
    it might be most straight forward to go with a screen that has already got drivers and sketch code available, with lots of different examples.
    I agree, it would be more straight forward, but so far I cannot find one that fits my size requirements.

    I know there are libraries that exist for DOGM but I am just not certain how to wire the circuit (or indeed what some of the components in the circuit are for ).

    Btw, thanks for the link to the microSD guide. Once I have got the LCD connected to the teensy, is it just a matter of following the microSD guide to connect it and then I will be able to read from a microSD card and display it on the LCD? Or am I missing something?

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    Senior Member+ MichaelMeissner's Avatar
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    Are you reading plain text from the SD, or is it encoded in some fashion, such as epub format. If it isn't plain text, you will need appropriate software to decode the formats.

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    Plain text.

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    Senior Member+ MichaelMeissner's Avatar
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    Plain text simplifies things.

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    Senior Member PaulStoffregen's Avatar
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    Look in Arduino's menu: File > Examples > SD > DumpFile

    It reads "datalog.txt" from the SD card and prints it to the Arduino Serial Monitor. You can start with that, and once it's printing the file to the serial monitor, add some code to slow it down to one LCD screenful at a time. Get that working in the serial monitor first. Then add the LCD.

    That's how projects are done... one step at a time, getting each piece working and tested. You build up as you go.

    This new board makes connecting the SD card simple for Teensy 3.1. The old SD adaptor can be used too, but since it was designed to mate nicely to the pinout of Teensy 2.0, wires are needed to match it up to the right pins on a Teensy 3.1.

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    Thanks for all the advice PaulStoffregen

    Currently waiting for my Teensy to arrive in the post.

    When I'm up to the stage where I am connecting the LCD, should I connect it up as you have showed here http://forum.pjrc.com/threads/24237-...ll=1#post35653 ?
    (Is there a schematic somewhere that makes it easier to follow?)

    Also in those photos, what are the buttons, potentiometer(?) and resistor doing?

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    How can I power the Teensy 3.1 by battery?

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    Senior Member mortonkopf's Avatar
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    You can connect up a battery supply o the Vin and grd, have a read of how to ensure no issues with the usb power:
    http://www.pjrc.com/teensy/external_power.html

    this image shows a 4XAA battery pack powering the teensy 3.1 and the cc3000 wifi board using common vin and grd connection points.
    Click image for larger version. 

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    Thanks mortonkopf
    Nice looking project.

    If I don't plan on using the USB, (except to upload my code initially), I won't need to fiddle around with cutting the pads or using diodes will I?

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    Senior Member mortonkopf's Avatar
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    cutting the the usb pads is a good idea, and not too difficult, and can also be reversed with a dab of solder later if you want to use the teensy for a different project. I have not used the diode method on any of my mobile battery powered projects as they are always away from a usb power source other than code changes. Cutting the pads is as simple as scoring a line between the pads with a sharp edge.

    Note that if you cut the pads you will need to power from the external source for all of the teensy activity.

    Alternatively, you can leave the pads joined, and only connect external source after disconnecting the usb, but this will mean the Teensy has no power for a while. The idea is to protect your computer and the Teensy.
    Last edited by mortonkopf; 01-25-2014 at 10:31 AM.

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