Reply To: New Koryuu test firmware 1.1-test1

[megari]

@aotta Thank you for your efforts in troubleshooting this. It does indeed look like your LSF0204 (designation U2) is not working. Bypassing it is perfectly fine, although it is preferable to use a 3V3 logic HIGH level [1].

PC3 (pin 26) is not connected to anything, so no harm was done there, fortunately.

May be my LSF0204 is gone? I found in a Texas Instruments’ datasheet that pins 6 and 9 are not connected in TSSOP 14 pin LSF0204, while in Koryuu they are used.. could it be related to my issue?

Pins 6 and 9 in the 14-TSSOP package LSF0204 are indeed not connected internally. However, those two pins are not used in the Koryuu. The other pins are used as follows:

• Pin 1: 3V3 IO voltage reference
• Pin 2: 3V3 MISO
• Pin 3: 3V3 MOSI
• Pin 4: 3V3 SCK
• Pin 5: 3V3 /RESET
• Pin 7: GND
• Pin 8: EN (connected to 3V3, so always enabled)
• Pin 10: 5V /RESET
• Pin 11: 5V SCK
• Pin 12: 5V MOSI
• Pin 13: 5V MISO
• Pin 14: 5V I/O voltage reference

All the 3V3 pins are connected to the MCU, while the 5V pins are connected to the ICSP header.

Thank you for your support!

Thank you for your efforts! You have been very patient while remotely troubleshooting this kind of a frustrating problem.

I wonder if you could check one more thing for me, please? I’d like to see a photo of the LSF0204 chip that was used on the board, or alternatively, know all the markings on said chip. That would be helpful in ascertaining that there isn’t a wider problem.

I have been intending to release somewhat simplified schematics and other technical information helpful for firmware development for quite a long while now, but this year has not been nice (to say the least), delaying these plans.

[1] The atmega328p is tolerant to 5V logic, but there may be issues in the long term due to the extra voltage causing current through protection diodes to GND and/or VCC. Due to this, all pins except /RESET have an absolute maximum rating of VCC + 0.5V, with VCC equal to 3V3 here.