Skywire
®
Cellular Modem
Hardware Developer’s Guide
NimbeLink Corp
Updated: April 2020
PN 1001594 rev 3 © NimbeLink Corp. 2020. All rights reserved. 1
Table of Contents
Table of Contents 2
Introduction 4
Skywire Modem Overview 4
Skywire Modem Categories 4
Design Resources 5
Mechanical Drawing 7
Skywire Pin Description 8
System Architecture 10
Skywire Integration 12
Serial Communications 12
Serial UART Interface 12
USB Interface 13
Power 13
Power Supply design Guidelines 14
Power Control 15
ON_OFF Signal 15
Shutdown 15
VREF 16
DTR/WAKE 17
Status Monitoring 17
Ring Indicator 17
GPIOx 17
Power Monitoring with a modem’s GPIO pin 17
SIM Cards 17
ESD 18
Layout & Schematic Considerations 18
Layout Examples 18
Enclosure Considerations 21
Skywire Antenna Considerations 22
Skywire Antenna Connections 22
Antenna Considerations 22
System Verification 24
Operational tests 24
PN 1001594 rev 3 © NimbeLink Corp. 2020. All rights reserved. 2