Epyon
Well-known member
Hello all
I recently made a custom board based on the Teensy 3.1 schematic available from Paul. The board uses the MK20DX256VLH7 microcontroller together with the Mini54 TQFP chip from the PJRC store.
My schematic is an almost identical copy of the one of the Teensy 3.1, save for the on-board 3.3V regulator and a combined reset for both 3.3V en 5V logic (I have some 5V components on the board as well). However, when connecting the board via USB, nothing happens. The MK20 and Mini54 receive power but aren't booting: the MK20 USB interface isn't recognized by the computer, and even the clock crystal doesn't seem to be oscillating. It's the same when I power the board externally (not via USB).
I've added a flywire to connect VREGIN to the USBVCC, but this doesn't have any effect (VREGOUT reads 3.3V).
I've included the schematic below. I don't really see where I could have missed something. According to the MK20 manual, the chip doesn't require special power up routines, but even when it has power it just wont boot. I have two boards, but it's the same with both.
Any help would be much appreciated!
*update*
By adding a 0,1µF capacitor between VREGOUT and GND there is a slight improvement in functionality. When connecting the USB cable, the board still isn't recognized by the PC. However, when I now press the program button the board is recognized, but as a USB HID input device - not as a serial port..
I recently made a custom board based on the Teensy 3.1 schematic available from Paul. The board uses the MK20DX256VLH7 microcontroller together with the Mini54 TQFP chip from the PJRC store.
My schematic is an almost identical copy of the one of the Teensy 3.1, save for the on-board 3.3V regulator and a combined reset for both 3.3V en 5V logic (I have some 5V components on the board as well). However, when connecting the board via USB, nothing happens. The MK20 and Mini54 receive power but aren't booting: the MK20 USB interface isn't recognized by the computer, and even the clock crystal doesn't seem to be oscillating. It's the same when I power the board externally (not via USB).
I've added a flywire to connect VREGIN to the USBVCC, but this doesn't have any effect (VREGOUT reads 3.3V).
I've included the schematic below. I don't really see where I could have missed something. According to the MK20 manual, the chip doesn't require special power up routines, but even when it has power it just wont boot. I have two boards, but it's the same with both.
Any help would be much appreciated!
*update*
By adding a 0,1µF capacitor between VREGOUT and GND there is a slight improvement in functionality. When connecting the USB cable, the board still isn't recognized by the PC. However, when I now press the program button the board is recognized, but as a USB HID input device - not as a serial port..
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. I'll check if I can find the board again in my lab next week.