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Serial port test

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  • Serial port test

    Have a simple question can i connect RX1 to TX1 on my uLCD and send some data to see if the port is working ? I have a gps module and i checked the tx on the module with a scope all seems fine, but no data on my µLCD-32PT(GFX)


  • #2

    Well you could, but it 'must' work. If you can write programs and/or PmmCs then TX and RX are working.

    Can you show a circuit of how the GPS is connected?

    Which GPS is it and when you say you can see the data with a scope, can you also see what speed the data is received at and whether it is valid?


    • #3

      Is it not COM0 for the programming port ?


      • #4

        Duh, sorry, I thought he was talking about Com0.

        Could always try the GPS on Com0.

        Could also try connecting tx0 to rx1 etc, to identify the pin if tx1 to rx1 fails, but really it must be rx1 (assuming that's what it is) as the GPS doesn't need to be sent to


        • #5

          This why I mentioned TX1 and RX1 I relize that com0 is used for uploading.

          The GPS module is GPS-PA6B-DIP Bought all my products from 4D !

          I have 2 other slave chips a DAC and ADC using Ic2 protocol and both are working correctly.

          Pwr, battery backup, for the GPS, 3.3v from the lcd max 400ma.

          GPS consumes only 50ma I figure that the ripple volts is less than 50mv being that it is powered by LCD no ferrite bead.

          GPS TX to RX1 of the lcd with a 68 ohm resistor in series.

          Ran the gambit of baud rates starting at 4800bps GPS default is 9600bps

          The 3d fix indicator is working correctly

          simple code to test

          com_SetBaud(COM1, 480); // To set Com1 to 9600 BAUD rate.

          var char;
          char := serin1(); // test the com port
          if (char >=0)print(char); //


          Is there anything that i missed LOL

          Second question I noticed that there is a 47k pullup resistor (R17) connected to 3.3v on Com0 RX of the lcd close to connector CN1 when looking at the schematic of the lcd. Question if I would connect some other serial TTL on com0 how would it be affected by the pullup resistor ? I guess I could use your µUSB-CE5 and the gps TX to connect to hyper terminal winxp ?


          • #6

            Getting it going under hyperterm is probably the easiest, maybe. It should be ok with the CE5.

            Maybe try reading through this


            • #7

              if GPS default is 9600, I would set com_SetBaud(COM1,960); straight up.

              Also, if the GPS is a 3.3V device, I wouldn't worry about a series resistor.. just GPX_Tx --> 4D_Rx1, etc..

              MicroLec Industries P/L