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C2000 launchpad external power supply ans serial communication problems

Duong Tam
Prodigy 160 points

Other Parts Discussed in Thread: MAX232, CONTROLSUITE

to get standalone status of C2000 launchpad (SCI-A), I supply a 5v power to pin 1 (+) and pin 2 (-) of header J5 as schematic. It seems be ok, but tx and rx leds of SCI status are always on although I don't send or receive anything via scia. Because of this I couldn't observe my communication status. I think it's a bug, isn't it ?

another question, I don't want to use virtual com port via mini usb interface, I've put S4 to DOWN and connected pin 3&4 of header J1 with COM port of my desktop via max232 (my max232 circuit works fine). I can't receive any tested character I sent on my terminal program in PC. Would I need anymore setup to complete this communication? (if connected via mini usb, terminal program can receive character as well). I know that max232 require TTL of 5v input, but TTL signal of c2000 is only 3v3, is that totally ok ?

Anyone can help me please, all advices should be appreciated :)

Thanks,

Tam

  • 0
    Guru 192875 points

    Hi Tam,

    Duong Tam said:
    It seems be ok, but tx and rx leds of SCI status are always on although I don't send or receive anything via scia. Because of this I couldn't observe my communication status. I think it's a bug, isn't it ?

    Which LEDs are you talking about? Can you name them on C2000 Launchpad schematic? As far as I remember there are no such LEDS.

    Duong Tam said:
    Would I need anymore setup to complete this communication? (if connected via mini usb, terminal program can receive character as well). I know that max232 require TTL of 5v input, but TTL signal of c2000 is only 3v3, is that totally ok ?

    MAX232 level shifter circuitry is enough. 3.3V TTL works perfectly well with MAX232 IC and I've implemented the same. You don't need any other circuitry; just check the pulses using DSO. Also, the sample code in controlSuite is implemented for 9600 baud rate.

    Regards,

    Gautam

  • 0 in reply to Gautam Iyer
    Prodigy 160 points

    Thanks for your quick response.

    Those are D7& D8, which are signed TX&RX in the Launchpad, in the corner near FTDI chip& JP2. When transmitting or receiving data, the respective LED will blink to notify our transmission. With external power, they are always on !

    In my project, it needs 115200 baud rate to communicate with the radar(can't change!), so that I've changed baud rate to 115200 in the sample code, I've tested output with terminal program(via mini usb port) that the code also works fine. Is that config ok if I connect J1.3& J1.4 instead of virtual com port ?

    max232's datasheet said that it could work fine with rate up to 120kbps. We need the rate at 115.2 kbps, I think it will be ok, isn't it ?

    Regards,

    Tam

  • 0 in reply to Duong Tam
    Guru 192875 points

    Duong Tam said:
    Those are D7& D8, which are signed TX&RX in the Launchpad, in the corner near FTDI chip& JP2. When transmitting or receiving data, the respective LED will blink to notify our transmission. With external power, they are always on !

    Ok, yes they're related to FTDI chip and indicate the SCI transfers. They should blink only while transmission; as you've mentioned above that the transfers take place without any issue... this seems like a glitch. On my launchpad, I'm not able to observe that though!

    Duong Tam said:
    In my project, it needs 115200 baud rate to communicate with the radar(can't change!), so that I've changed baud rate to 115200 in the sample code, I've tested output with terminal program(via mini usb port) that the code also works fine. Is that config ok if I connect J1.3& J1.4 instead of virtual com port ?

    Yes, J1.3 & 1.4 are perfect. Are you able to observe the data waveform in and out from MAX-232?

    Regards,

    Gautam

  • 0 in reply to Gautam Iyer
    Prodigy 160 points

    Oh, they all works very well. Maybe, the 2 LEDs with external power have some bugs that in this mode we can't observe the transmission via tx rx leds :)

    Thanks for your help.

    Regards,

    Tam

  • 0 in reply to Duong Tam
    Guru 192875 points

    Duong Tam said:
    Oh, they all works very well.

    So, your max232 circuit is working now or not? If not, can you share the max232 circuit schematic you're using?

    Here's a sample circuit that should have a common ground.

    Regards,

    Gautam

  • 0 in reply to Gautam Iyer
    Prodigy 160 points

    Hi Gautam,

    I'm working on a project that sends control signals to the transceiver, and receives data back to launchpad via COM port of this device. My max232 circuit is the same as yours, and it works well.

    With your helpful advices, everything is now ok and I can process data easily. It's my fault that I forgot adding a delay after each of my control singals so that the transceiver couldn't receive it (and so that couldn't send data back), launchpad and max232 all work fine when I observe their signal with a DSO.

    Regards,

    Tam

  • 0 in reply to Duong Tam
    Guru 192875 points

    Duong Tam said:
    With your helpful advices, everything is now ok and I can process data easily. It's my fault that I forgot adding a delay after each of my control singals so that the transceiver couldn't receive it (and so that couldn't send data back), launchpad and max232 all work fine when I observe their signal with a DSO.

    That's Great, Tam!

    Goodluck & Regards,

    Gautam