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proposal for user-defined VDD switching

2025-03-18
2025-03-19
  • Dan Skareda

    Dan Skareda - 2025-03-18

    First of all, I praise the programmer project, it is great. I built it, but I program the circuits in HVP mode by connecting the breadboard to the chip using VPPU-VDDU-GND-PGD-PGC. But the problem with this method of programming is that it uses a switched VDD and 5V cannot be obtained on VPPU, so without switching the wires, the circuit cannot simply be put into the RUN state after programming (at least because VDDU turns off). Did the author consider a three-state level on VPPU (13V-5V-0V for example, by using only one LED)? That would solve this problem - put VPPU to 5V and turn on VDDU, the programmed circuit could be tested immediately without switching the wires... Chips from other manufacturers are programmed differently (e.g. UPDI on Attiny/Atmega) and this method of programming/testing is very practical. Oh, and nowhere in the description did I find when LEDs are on and when they are blinking - can you describe it in detail?

     

    Last edit: Dan Skareda 2025-03-18
  • Alberto Maccioni

    In order to enter program mode, each device needs a specific sequence of voltages on VPP and VDD. This is not the same for every one of them; some allow both VPP first and VDD first, some not. Anyways, controlling both voltages is the safest approach.
    You can enable VDD manually from the I/O tab, however there is a limit to the current that the programmer can supply (also consider that the USB port has a limit as well).
    In fact, documens from Microchip suggest to put a jumper in the vdd line when using ICSP; this is to only power the device in program mode and not the rest of the circuit.
    You can do it but be aware of the risk.
    Finally, you can find the description of LED1-2 on the "communication protocol" chapter on the project website.
    "The state of USB connection is signaled by LED2: it blinks at 4 Hz during enumeration, at 1 Hz in normal operation.
    LED1 shows when there are instructions being executed."

     
  • Dan Skareda

    Dan Skareda - 2025-03-19

    Thanks for the answer. I've only been using the command line so far because opgui.exe didn't recognize the programmer. I'll try to find where the problem is and use opgui.exe. I didn't know that I could choose the VPP voltage there according to my own requirement. That's great!

     

    Last edit: Dan Skareda 2025-03-19
  • Anonymous

    Anonymous - 2025-03-19

    In case of op the procedure is slightly more complicated because there is no explicit option for controlling I/O lines (I may add it in the future); you have to use the -command option to send direct commands to the programmer.
    Instruction EN_VPP_VCC (0x0E) controls the power lines with bits 0 and 3 of its argument.
    So you can type:
    op -command 0E 1
    for turning VCC on,
    op -command 0E 4
    for VPP,
    op -command 0E 5
    for both.

     

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