2.8" TFT combined with GPS Shield.

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Aerosonic
 
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Joined: Sun Jun 14, 2015 2:14 am

2.8" TFT combined with GPS Shield.

Post by Aerosonic »

Dear Adafruit.

Before I get too deep into my project of creating a GPS/Magnetic Compass/UTC Time Clock; I need to ask a few simple questions. I plan to use the following:

Arduino Uno R3 - No. 50
Adafruit GPS Shield - No. 1272
Adafruit 2.8" TFT Touch Shield (Capacitive) - No. 1947
Adafruit Triple-axis Magnetometer (Compass) Board - HMC5883L - No. 1746 (this may need to be upgraded to No. 1120)

My first question is that I don't understand the "Pinout Section" starting on page 9 in "Adafruit 2.8" TFT Touch Shield v2 - Capacitive or Resistive" (file: adafruit-2-8-tft-touch-shield-v2.pdf). Specifically, what does the text mean "By cutting a jumper (I don't see a jumper) and soldering another on the back, you can move this line". Why would you do this and how would it be done? Why not just use the six pin ICSP?

My second question is that the GPS Shield and TFT Display both appear to be using pin 10. The GPS has a line of code that specifies "#define chipSelect 10" found in "Adafruit-GPS-Library-master.zip" under "examples/shield_sdlog/shield_sdlogg.ino on line 35. The TFT Display as described "Pinout Section" starting on page 9 uses: "Digital #10 - This is the TFT CS (chip select pin). It's used by the Arduino to tell the TFT that it wants to send/receive data only from the TFT". Does this cause a conflict? Is it possible to use both memory chips on each shield? Is there a way to change the pin number on one of the shields so there wouldn't be a conflict?

My idea is to put GPS data on the memory chip using the GPS shield and to store compass images (bit maps) on the memory chip found on the TFT shield. The touch screen would be used to bring up different images and data. At this time I have no code or schematics as I am at the beginning and just found some conflicts that I may need to deal with. If you have any suggestions please pass them along.

Best Regards

Walt (a.k.a AeroSonic)``

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adafruit_support_rick
 
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Joined: Tue Mar 15, 2011 11:42 am

Re: 2.8" TFT combined with GPS Shield.

Post by adafruit_support_rick »

You need to solder some jumpers on the back of the TFT to enable SPI on the ICSP pins. You would only need to cut the traces to pins 11, 12, and 13 if you wanted to use those pins for some other purpose.

The TFT uses Pin 10 as a chip select line for the TFT itself, and it uses pin 4 as the chip select line for the SD card. These pins are exclusive - you can't use them for anything else.

The GPS Shield also uses Pin 10 as a chip select for the SD card. So you can't use the SD card on the GPS along with the TFT, as this is a conflict. To resolve the conflict,
you can move the GPS chip select to a different pin by cutting the trace between CCS and pin 10, and jumpering from CCS to some unused pin.

HOWEVER, you really don't want to use both SD cards. You won't have enough SRAM on the Uno to do this. You are much better off using just the SD card on the TFT, and leaving the one on the GPS shield empty (you won't need to cut any traces or install any jumpers on the GOS if you don't use the SD card).

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