Hi,
where have I to connect an external power supply, if I cut away and don't use the midi pcb part?
Should I powered it with 3,3V DC or 5V DC and can the axoloti be powered by an external source while it is connected to a USB source? with midi pcb part this is possible and the external powering is preferred by the axoloti core.
Ex-/internal power management
paul
#1
johannes
#2
Supply (regulated!) +5V, and keep the on-board linear regulators, you can find a pair of solder holes labeled "+5V" and "G". You can also find the same signals on JP3.
The MIDI/power part can be sandwich-mounted to the main part, the mounting holes line up. But that is optional.
There is reverse current protection on the USB device port (and also on the USB host port).
You can monitor the voltage of the +5V and VDD (3.3V nominally) power rails in the software, it's real time updated in the main window.
paul
#3
ok, but if the MIDI/power part is cutted, there are no extra +5V/GND pads besides JP3 solder pads?
the circuit for a external powering should be look like this:
johannes
#4
ok, but if the MIDI/power part is cutted, there are no extra +5V/GND pads besides JP3 solder pads?
There is a pair near PA4 too.
the circuit for a external powering should be look like this
This will work, but your linear regulator will overheat if you use high-current devices on the USB host port.
When a device connected to the USB host port drinks 500mA current (the legal usb maximum current), the regulator will burn 1W if you feed it 7V, and 3.5W if you feed it 12V, just for the USB host port. Will need a serious heatsink.
For this reason, the MIDI/power part has a switching power supply, which is far more efficient. I suggest to reuse that part.
[Need Help with SPI] Euxoloti for axoloti (Eurorack Module)
paul
#5
thank you for the informations. if usb host isn't used, it should work. I want to mount the midi/power part at a separate panel as an option for midi in/out.
I will measure the current drain of my circuit.
nathanxl
#6
Im not clear if it helps out my queries.
I have my core with the MIDI part cut off.
I want to power it from an external power supply of 5VDC.
If the external power is soldered to holes +5V and G near PA4 AND I have the mini USB port connected to my computer will there be a problem?
Thanks
johannes
#7
The ST2161 (U4) will block reverse current into micro-USB. Still, if both external power and the micro-usb are connected, it is not sure that current will be drawn from the external power supply, it will depend on the exact voltages.
The switching power supply part disables USB bus powering when external power is present, by disabling the ST2161.
Also keep in mind that the +5V is assumed to be regulated and stable, it should not exceed 5.25V for the USB host plug to stay in spec.
