Outputs (GPIOs, I2S, SPI) on the M100
The M100 converts the 1.8V level output signals to 3.3V. It uses a bidirectional level converter, which
automatically detects the direction of the signal. For the level conversion to work properly, caution must be
taken, if there is a pull-up resistor on any output. This applies to all outputs including GPIOs and special
function outputs like SPI, I2S. If there are any pull-up resistors on these outputs, they must have more than 50
kOhm. If there is a pull-up resistor with a lower value, than the level converter may determine that the signal
is driven from the outside, and that this pin should be treated as input.
LEDs
The 12V power LED will light up as soon as the power is connected to the M100, independent of whether a
J100/J106 is plugged in. The 2 on-board DC converters only power up if a J100 or J106 is plugged in.
Buttons
UART 1 (J7)
This is a TTL level (3.3V) UART port of the TX1/2. The 2 pins are passed through a bi-directional level
converter with 3.3V level outputs (TXB0104PWR) and through 33 Ohm series resistors (in a tiny 0804 size
resistor array).
USB 2.0 (J17)
USB 2.0 port for firmware upgrades and for USB 2.0 devices like mouse and keyboard.
