5 Replies Latest reply on May 11, 2017 1:22 PM by Intel Corporation

    I2C PN532 NFC shield and I2C character lcd

    rachael_123

      Hi,

       

      If i connect NFC shield and lcd by using wire, NFC shield is connected to pins A4 and A5 pins and LCD is connected to SDA and SCL pins, "didn't find pn53x board" sometime appear sometime didn't appear. Fyi,  I using the Adafruit_NFCShield_I2C-master library and Arduino IDE. The message "didn't find pn532 board" showing on serial monitor when shield not working. I thought it is connection problem so that i soldered the connectors to attached the shield directly on the board. After soldering, i tested the shield alone on the board, it is working. I thought i solved the problem. But after i connect the lcd on the shield, "didn't find pn532 board" always show again. What is the problem? How can i solve?

       

      18362167_1534104886601562_1992058232_o.jpg

       

      And i did the scanning

       

      0x24 is address for my nfc shield and 0x27 is address for my lcd.

        • 1. Re: I2C PN532 NFC shield and I2C character lcd
          Intel Corporation
          This message was posted on behalf of Intel Corporation

          Hello rachael_123,

          Thanks for reaching out!

          I understand that you soldered the NFC shield to your Edison, but I would like to ask you if you were able to test both devices individually. I mean, it would be of great help if we knew for a fact that both the LCD and the NFC shield worked fine with Edison. If they would, then that would mean that the issue is not related to the LCD, the NFC shield or the Edison but instead power.

          I can see in the picture you shared above that you use the micro USB port to power the Edison, this power supply may not be enough and you might have to use an external power supply (through the barrel jack) to power all three devices (Edison, LCD and NFC shield).

          I would like you to try this and let us know if you see any difference.

          I hope this information helps you,
          Pedro M.

          • 2. Re: I2C PN532 NFC shield and I2C character lcd
            rachael_123

            Hi Pedro,

             

            Thank you for your reply.

            Yes. I had test both devices nfc shield and character LCD individually and they worked perfectly. However once i attached LCD to the shield (see Figure 1), nfc started to stop working, by showing "didn't find pn53x board" on serial monitor (see Figure 2). Once i detached the LCD from the shield again, the nfc working again (see Figure 3). I did connect power jack this time. I read the documentation for the nfc shield, they suggested that provide 3.3V external power source to the nfc shield. The LCD required 5V. By testing the nfc shield alone, if i connect nfc shield using wires, the signal was not stable, the nfc shield sometimes working sometime not working, not working means that  showing "didn't find pn53x board" on serial monitor (see Figure 2), thus i cannot seperate nfc shield from microcontroller. Do you have any suggestion?

             

            20170509_104243.jpg

                                                                                  Figure 1

            cxc.png

                                                     Figure 2

             

             

            xzx.png

                                                 Figure 3

            • 3. Re: I2C PN532 NFC shield and I2C character lcd
              Intel Corporation
              This message was posted on behalf of Intel Corporation

              I still believe this is related to power, I mean, if both devices are proven to work without issues on the board, then you shouldn't have issues using them at the same time if the sketch has not issues.

              What are the specifications of your power supply? I would suggest you to use a power supply of at least 2A and if possible, do not power the LCD and NFC shield directly from the Edison but instead power them directly from the external power supply. I mean, another possibility is that there is nothing wrong with your sketch, the devices or the power supply but it could be that the Edison lacks the capability of providing as much current as those devices need. Powering the devices directly from the power supply would eradicate this possibility.

              Let us know.
              Pedro M.

              • 4. Re: I2C PN532 NFC shield and I2C character lcd
                rachael_123

                Hi Pedro M.,

                 

                I changed to use conventional wiring for LCD instead of I2C, both LCD and RFID is working. Thus, i guess the problem is on I2C.

                 

                • 5. Re: I2C PN532 NFC shield and I2C character lcd
                  Intel Corporation
                  This message was posted on behalf of Intel Corporation

                  I see, I find really strange that the Edison was having trouble using both devices at the same time. Anyhow, I'm glad to hear that you are now able to use these devices without problems.

                  Thank you for sharing this workaround with the community, I'm sure this information will be of help for other users in the future.

                  Pedro M.