Lantronix PremierWave 2050 Integration Guide - Page 21

2: Functional Description Table 2-7 Example RS422/485 Connections (Serial Transceiver Required) PremierWave 2050 Signal (logic) TXDx TXDx RXDx RXDx RTSx CPx CPy Description Data Out Data Out Data In Data In TX Enable RS485 Select RS485 2-wire RS485 Signal TX+485 TX-485 RX+485 RX-485 DB25 4 Wire 14 15 21 22 DB25 2 Wire 14 15 14 15 DB9 4 wire 7 3 2 8 DB9 2 wire 7 3 7 3 Note: The IO pins for PremierWave 2050 module are set to floating input on power up until configured by unit firmware. An external 100K ohm pull-up may be required on the serial transmit signal to prevent downstream UART devices from detecting false characters on initial power up. Ethernet Interface The unit provides a 10/100 Mbps Ethernet interface for connection to an external network through external magnetics and an external RJ45. The figure below shows the Ethernet connections to a 10/100 Ethernet RJ45 Jack with Magnetics, J5 in the figure. The RJ45 Magnetic Jack is Belfuse part number 08B0-1D1T-06-F. The Ethernet differential pair signals, ERXM/ERXP and ETXM/ETXP should be routed as 100ohm differential pairs on a layer next to the signal ground plane. The use of vias on these signals should be minimized. Center tap signals RXCT and TXCT should be routed with at least 20 mil trace thickness. The area underneath the RJ45 magnetic jack should be void of all signals and planes. The connector shield should be connected to chassis. It is recommended that 1206 resistor pads from chassis ground to signal ground be placed next to each of the shield tabs. The resistor pads allow for 0 ohm jumper, ferrite beads, or decoupling caps to be installed as needed for EMI/EMC improvement. The Ethernet LED signals should be routed to discrete LEDs or to the LED pins on the RJ45 through 220 ohm or larger resistors. The LED signals are active low. Also shown in the figure is an optional active choke that can be used to improve ESD, EFT, and EMI/EMC performance in harsh environments. The device is shown as U22 in the figure and is Akros part number AS1602. This device features route through pin assignments allowing for the Ethernet differential signal pairs to be routed without altering the trace impedance or adding vias. Due to this routing the device could be installed or depopulated as needed. Lantronix has performed all certification to FCC Class B without U22 populated. The Ethernet signals may be left disconnected if unused. See the Lantronix app note, How to Connect a Lantronix Embedded Module to a Wired Ethernet Port for more details on Ethernet connection and routing, http://www.lantronix.com/pdf/appnotes/Connect-LTRX-Embed-Module-to-WiredEthernet_AN.pdf. PremierWave® 2050 Enterprise Wi-Fi® IoT Module Integration Guide 21