It doesn't work after a few hours of operation.

[AshiChu]

A few hours worked nicely OLED displayed a record on MicroSD worked. Now, but the OLED does not display and LED flashes on the GPS module. And the red LED does not light on the main board with Atmel chip. Charging works and battery voltage is 3.8V when charging is disconnected.

[hinner]

Is it any difference with or without SD-card? Is something written to the card? Does the blue LED flash from time to time and ticking is audible? GPS flashing LED does not mean anything special but tells you there is no problem with DC. If there is something written to the SD-card and the blue LED flashes, check OLED display connection. If not, check processor soldering. Happy easter Kajetan – Dr. K. Hinner, Dr. Hinner GmbH, Kochelseestr. 11, D-81371 München, St.-Nr: 143/130/60382       --- Unternehmensberatung mit Schwerpunkt IT - IT-Sicherheit - Datenrettung  ---                 -- Handel mit EDV und -Teilen, Windows Server - Linux - IT-Speziallösungen --                 -  HR München, HRB 242301 Geschäftsführer: Dr. Kajetan Harald Hinner - Am 19.04.19 um 08:57 schrieb AshiChu:

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A few hours worked nicely OLED displayed a record on MicroSD worked. Now, but the OLED does not display and LED flashes on the GPS module. And the red LED does not light on the main board with Atmel chip. Charging works and battery voltage is 3.8V when charging is disconnected. —

[AshiChu]

I desoldered apart the main board and the Arduino Fio board and the Arduino Fio board doesn't really react. The red LED is off only the orange LED is on when charging. I don't own FTDI serial converter so I ordered and try to do upgrade FW according to instructions. Maybe the Arduino Fio board will start working.