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Gen4-uLCD-70DT questions

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  • Gen4-uLCD-70DT questions


    We've been using the Diablo16 70DT for over a year, and now we are migrating to the newer gen4 version. As of now we are facing two problems with the migration:
    1. Since all the other hardware was built to function with the older models, which had the 30-pin header, now we have to adequate all the other hardware pieces to the new 30-way FPC cable. As a temporary measure and as means to check if everything still works with the newer displays before changing the rest of the hardware, we bought a gen4-PA board to solder all the wires from the old hardware - and here comes the first problem. We were using the 70DT to send and receive commands through serial communication using COM0, which worked fine with the old display. Using the newer gen4 display, we can see how the commands sent by the display are in the correct TTL range (0~3V3), but when receiving commands the signal is in 1V5~3V3 range, which causes the gen4 to be unable to receive them correctly. Doing some tests, the problem narrowed down to either the gen4 display, the FPC cable or the gen4-PA (but we bought a new gen4-PA board and the problem is still there. Checking the gen4-PA datasheet, it seems the RX0 and TX0 lines have a 68Ohm resistor on them, but we doubt it's that because then there would be a failure in both the RX and TX lines).
    2. We are planning to use a 5kNTC to monitorize the temperature of a piece of equipment. According to the gen4 datasheet, only PA0 to PA3 can be set as analog inputs with 0 to 3V3 range. Our team looked into it and it seems there are some issues with the input voltage range: the estimated resistance range of the NTC we will use is 4K~30K, according to calculations, feeding the circuit with 5V would mean a voltage range of 0.8V to 3V3, but if something happens with the NTC the analog pin will receive 5V, way out of tolerance. On the other hand, if we feed the circuit with 3V3 to prevent burning the input, the voltage range would drop to 0.5V to 2V, giving a much smaller resolution. Is the datasheet accurate on the tolerance of the analog pins?
    Thanks for your time.

  • #2

    I have tested a communication between an Arduino with DIABLO 70DT and DIABLO gen4 70DT and both displays received the same data. Can you explain more of your setup (connections and power source) while testing so that I can simulate here on my end?

    Just like what is documented in the datasheet, the maximum tolerable voltage of the analog inputs is 3.3V only. It could be connected to 5V but this is not recommended as it destroys the ADC of the display. You might find this useful for better resolution:

    Best Regards,


    • #3

      The setup is as follows (I hope it is somewhat understandable): the device we're using receives 24V from an external conversor, which is then further converted to 5V 2A using a DC/DCThe converter (R-78B5.0-2.0) to feed the display on a spearate board which acts as a bridge between the display and the driver board. The driver board requires RS232 signal, so the bridge board features a max3232-type chip to convert TTL to RS232. The bridge board connects to the 70DT via a 10-way IDC type cable, connected to a small board that attaches to the 70DT's 30-pin header. With the gen4 displays, we bought a few gen4-PA boards with the intention of keeping the bridge board as is for the moment, so we hand-made a small board that connects the IDC cable to the gen4-PA pins, and the gen4-PA connects to the gen4-70DT through the supplied FFC cable.

      Everything works except the serial communication when using the gen4-70DT, and the device works properly with a 70DT. We unwired everything on the hand-made board leaving only the bare minimum for the serial communications to work - +5V, GND, TX0 and RX0. Using the bridge board's test points, we can check the TTL signal sent from the gen4-70DT (correct signal), after converting to RS232-type (correct signal), the received RS232 signal from the driver board (correct signal) and after converting to TTL (wrong signal). Since the driver board sends information on startup via serial, we tested the received TTL signal without wiring the gen4-PA or the gen4-70DT; the signal received was correct TTL-level so that should rule out any issues on the other hardware (and to reiterate, the device including serial communcation works fine using a 70DT).

      Since we ended up with three gen4-PAs, a coworked tampered with it and found out that cutting the path leading to R5 on the gen4-PA (corresponding to the RX0 signal) makes the received signal be properly TTL-level.

      Thanks for providing us with that link, we'll take a look.

      Unfortunately I'll be on leave for two weeks, please excuse the delay on coming back to you.

      Thank you for your time.