AVR Programmer is an ISP programmer for AVR microcontrollers that offers faster programming than the ones that use a legacy serial port. The program comes with a simple circuit and built-in FTDI's official driver that makes it easy to use. One of the exciting features of this programmer is its built-in simple filer that enables you to log UART from MCU via MOSI pin.

AVR Programmer's logging UART feature is unique as it logs via MOSI, not MISO, and it is a non-inverting UART. The new line is CR or LF or CR+LF, and the only ASCII is supported. Additionally, in this mode, ADBUS0(TXD, SCK) and ADBUS2(RTS#, MISO) output H, and SCK/MISO are not able to use as GPIO. Please set their DDR to input. To use the program, check that your phone supports USB-OTG, and the phone catalog which Google Play has may be wrong. To make an adapter, the schematic is available in the app. However, the cost of parts is about US$20, and the PDI/TPI are not supported, which are next-generation interfaces. Only Intel HEX is supported, and if your phone cannot resume USB, you had better disable sleep.