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LCD Backpack only works with USB
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Please be positive and constructive with your questions and comments.

LCD Backpack only works with USB

by dannylgreen on Sun Feb 10, 2019 1:47 pm

Hello,

I recently purchased the USB + Serial Backpack kit, Product 782. I have soldered them together, and it works fine when testing with my computer using the USB cable. However, when I try it using an Arduino Uno, using the sketch provided in the 'Testing with TTL Serial' page of the tutorial, the LCD remains dark. The backpack has the red power LED. When the Arduinio is first powered, the backlight will flicker twice, so fast you can barely see it unless you watch for it. I have tried 2 different Arduino boards, and have double checked everything. I am fairly experienced with Arduino, so I don't think the issue is with loading the sketch or anything (I do get the Upload completed from the IDE). Any help would be appreciated.

Using LCD.jpg
Using USB it Works
Using LCD.jpg (640.98 KiB) Viewed 135 times


Using Arduinow Serial.jpg
Using Serial it doesn't work
Using Arduinow Serial.jpg (566.7 KiB) Viewed 135 times


Arduino Connections.jpg
Arduino Connections
Arduino Connections.jpg (733.42 KiB) Viewed 135 times


Thanks,
Danny

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Re: LCD Backpack only works with USB

by adafruit_support_carter on Sun Feb 10, 2019 2:51 pm

Looks like you might be doing some additional jumpering from the supplied JST pigtail cable to some other wires that actually go to the UNO?

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Re: LCD Backpack only works with USB

by dannylgreen on Sun Feb 10, 2019 3:23 pm

Hello,

I have connected short pieces of solid wire to the ends of the pigtail using butt connectors to allow me to insert them into the Arduino. I've used this technique in the past without problems, is it possible this is the issue? I redid the white TX wire in case the connection was bad (though these connectors typically work very well). I figured the power wires were OK as the power LED is lit on the backpack.

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Re: LCD Backpack only works with USB

by dannylgreen on Sun Feb 10, 2019 3:50 pm

Ok, so I put jumpers from the TX Grnd, and 5v holes on the backpack to the Ardunio, and like this the backlight for the LCD lights, but there is no text displayed.

JumpersToUno.jpg
Jumpers to Uno
JumpersToUno.jpg (948.96 KiB) Viewed 118 times

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Re: LCD Backpack only works with USB

by adafruit_support_carter on Sun Feb 10, 2019 4:13 pm

Try using those jumpers wires and hook up the display same as I did below. I just tested that sketch on the Learn page and it's running OK for me. Since yours is working with USB, seems like some form of connection issue with the TX line.
lcd_test.jpg
lcd_test.jpg (114.46 KiB) Viewed 115 times

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Re: LCD Backpack only works with USB

by dannylgreen on Sun Feb 10, 2019 5:04 pm

Hello,

This is exactly how I have hooked it up. Both from the connector, and to the holes directly on the backpack. Was there something specific that I should do differently?

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Re: LCD Backpack only works with USB

by adafruit_support_carter on Sun Feb 10, 2019 5:15 pm

Oh, sorry. Realizing now that I added that extra connector to mine a while back. The JST cable as shipped comes unterminated on the other end.

Using the holes like you show won't be secure enough to insure a good signal. I would think the crimp connection you had in your original photo would work OK though. Go back to that approach and double check that it's solid. Also check your soldering on all the pins here, on both sides of the connector:
pins.jpg
pins.jpg (69.54 KiB) Viewed 108 times

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Re: LCD Backpack only works with USB

by dannylgreen on Sun Feb 10, 2019 6:09 pm

Hello,

I redid my connections to the jst, but that didn't help. I also tried soldering the connections on the backpack, see the pictures below. I still get no text to display.

20190210_165328_resized.jpg
20190210_165328_resized.jpg (771.63 KiB) Viewed 101 times


20190210_165338_resized.jpg
20190210_165338_resized.jpg (772.14 KiB) Viewed 101 times


20190210_165445_resized.jpg
20190210_165445_resized.jpg (624.5 KiB) Viewed 101 times


Is it possible there is something wrong with the backpack so that only USB works but not serial?

Thanks!
Danny

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Posts: 27
Joined: Mon Dec 28, 2015 4:10 pm

Re: LCD Backpack only works with USB

by dannylgreen on Mon Feb 11, 2019 12:18 pm

Hello,

Above it mentions checking the soldering between the backpack and the LCD, however if there was an issue there, it seems like using USB wouldn't have worked.

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Re: LCD Backpack only works with USB

by adafruit_support_carter on Mon Feb 11, 2019 12:47 pm

The solder touch up was just to make sure, but agrees, seems like if there was an issue there, it would have affected USB also.

For the direct solder connections, the white wire should go to RX. The pin on the JST is labeled TX, but it's actually RX (confirmed with multimeter).

But it should notionally work through the JST with the connections you've shown. Not sure why that is not working. Do you have a multimeter?

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Re: LCD Backpack only works with USB

by dannylgreen on Mon Feb 11, 2019 12:54 pm

I do have a multimeter, what should I test? Also, I will try direct to RX.
Note that with the JST, the backlight of the LCD didn't even light up.

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Re: LCD Backpack only works with USB

by adafruit_support_carter on Mon Feb 11, 2019 1:28 pm

Connect your JST cable with the crimped solid core wire. Then do a continuity test between the end of the white wire and the RX pad on the header row of the backpack.

Between here:
white_wire.jpg
white_wire.jpg (44.54 KiB) Viewed 72 times


and here:
RX_pad.jpg
RX_pad.jpg (47.29 KiB) Viewed 72 times

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Re: LCD Backpack only works with USB

by dannylgreen on Mon Feb 11, 2019 1:41 pm

Excellent, I will test the continuity of the red and black jst also (though the power LED on the backpack lights with jst, so it seems that must be good).

I am at work right now, so it won't be until this evening that I can do the testing.

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Posts: 27
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Re: LCD Backpack only works with USB

by dannylgreen on Mon Feb 11, 2019 7:07 pm

Hello,

I tested continuity on all 3 wires for the JST connector, and all three tested good.

I also switched the direct connected white wire to the RX connection. Now I get garbled flickering text when I run (this is with the direct connection JST is just dark):

20190211_174548_resized.jpg
Example sketch
20190211_174548_resized.jpg (186.05 KiB) Viewed 56 times


I also simplified the sketch, removing the special character and just having it print 'Hello World ', and the code in the loop to change the RGB background:

20190211_174625_resized.jpg
Simplified Sketch
20190211_174625_resized.jpg (171.68 KiB) Viewed 56 times


Here it is stable without the loop, but still garbled.
I also checked the version of SoftwareSerial, and it is Built-In by Arduino version 1.0.0

Thanks!
Danny

dannylgreen
 
Posts: 27
Joined: Mon Dec 28, 2015 4:10 pm

Re: LCD Backpack only works with USB

by dannylgreen on Tue Feb 12, 2019 7:04 am

Here is the code for my 'Simplified' version:

Code: Select all | TOGGLE FULL SIZE
#include "Arduino.h"

#if defined(ARDUINO_ARCH_SAMD) || defined(__SAM3X8E__)
  // use pin 18 with Due, pin 1 with Zero or M0 Pro
  #define lcd Serial1 36+0
#else
  #include <SoftwareSerial.h>
  // Create a software serial port!
  SoftwareSerial lcd = SoftwareSerial(0,2);
#endif

// for ESP8266 use this SoftwareSerial library: https://github.com/plerup/espsoftwareserial

void setup() {
  lcd.begin(57600); 
 
  // set the size of the display if it isn't 16x2 (you only have to do this once)
  lcd.write(0xFE);
  lcd.write(0xD1);
  lcd.write(16);  // 16 columns
  lcd.write(2);   // 2 rows
  delay(10);       
  // we suggest putting delays after each command to make sure the data
  // is sent and the LCD is updated.

  // set the contrast, 200 is a good place to start, adjust as desired
  lcd.write(0xFE);
  lcd.write(0x50);
  lcd.write(200);
  delay(10);       
 
  // set the brightness - we'll max it (255 is max brightness)
  lcd.write(0xFE);
  lcd.write(0x99);
  lcd.write(255);
  delay(10);       
 
  // clear screen
  lcd.write(0xFE);
  lcd.write(0x58);
  delay(10);   // we suggest putting delays after each command
 
  // go 'home'
  lcd.write(0xFE);
  lcd.write(0x48);
  delay(10);   // we suggest putting delays after each command

  lcd.print("Hello World ");
 
 
  delay(1000);
}

uint8_t red, green, blue;
void loop() {

}


Thanks!
Danny

dannylgreen
 
Posts: 27
Joined: Mon Dec 28, 2015 4:10 pm

Please be positive and constructive with your questions and comments.