Users Manual

ITM-1066A User Manual
Proprietary & Confidential Information iotTech Corporation, Taiwan
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6. Hardware Design Guidelines
6-1 Reference Design
GPIO3 and GPIO13 must be HIGH when power-on.
GPIO20 MUST be LOW when power-on (A 100K-ohm pull-low resistor is recommended)
J3A and J4A are for firmware upgrade through USB interface – Pulling up GPIO14/15 when
power-on will force the module enter USB mode for firmware upgrade.
However, J3A and J4A must be as close to GPIO14/15 pins as possible. Otherwise, the PCB
traces of GPIO14/15 may cause EMI problem, because GPIO14 and GPIO15 are SPI flash
clock/data pins when the module is in normal operation mode.