MaxLinear XR21B1420IL28-0A-EVB USB to RS-232/422/485 Evaluation Board

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Overview

USB to serial evaluation board. Supports RS-232, RS-422, and RS-485. Made by MaxLinear, formerly Exar. Supposedly supports higher than usual baudrates, up to 12Mbaud.

MaxLinear XR21B1420IL28-0A-EVB | DigiKey

MaxLinear XR21B1420IL28-0A-EVB | Mouser

Wiring Diagram

DB9 Pin RS-232 RS-422 RS-485
1 DCD TX- Data-
2 RXD TX+ Data+
3 TXD RX+
4 DTR RX-
5 (GND)
6 DSR
7 RTS
8 CTS
9 RI
  • Page 5 of the SP339E datasheet shows the DE9 pinout

Jumpers

Name Default Function
J2 1 & 2 (down) 1 & 2 (down): VCC_OUT to VCC_TRANS
2 & 3 (up): VCC_USB to VCC_TRANS
J3 pins map to DE9 connector, except pin 5 (GND) is skipped
J4 47k pull-ups to VCC_TRANS for jumpering to J18
J10 1 & 2 (right) 1 & 2 (right): VCC_USB to VCC_UART
2 & 3 (left): VCC_3V3 to VCC_UART
J11 (not present) 1 & 2 (left): VCC_OUT to VIO
2 & 3 (right): VIO_EXTERNAL to VIO
J12 1 & 2 (down) 1 & 2 (down): GPIO7/!RI/!RWK to SW1 button
2 & 3 (up): GPIO7/!RI/!RWK to !RI_TRANS
J13 2 & 3 (left) 1 & 2 (right): VIO to VCC
2 & 3 (left): VCC_OUT to VCC
J15 2 & 3 (up) 1 & 2 (down):
2 & 3 (up)
J17 2 & 3 (up) 1 & 2 (down): TXT_MODE1 to TXT
2 & 3 (up): pullup/D1 LED to TXT
J18 ??? TODO
J19 (not present) 1 & 2: connects the regulated 3.3V from the SP6260 to the VCC pin of the XR21B1420
J20 1 & 2 1 & 2: GPIO9/!DSR to !DSR (transceiver) NOTE: manual claims GPIO2? schematic says GPIO9...
J21 1 & 2 (down): XEN to J37 pin 3
2 & 3 (up): !RTS_XEN to J37 pin 3
J23 ...
3 & 4: VCC_USB to !RESET
...
J24 (various debug signals)
J37 ...
3 & 4 (2nd from left): XEN or !RTS_XEN to DIR1
...

Software

To get full functionality under Linux, you must install the xr_usb_serial_common kernel module. The drivers are available here:

Software Drivers - MaxLinear

In the "USB UART" section in their downloads table, pick the latest version for Linux. Here is a direct link to version 1D for "Linux 3.6.x and newer":

xr_usb_serial_common_lnx-3.6-and-newer-pak_v1d.zip

xr_usb_serial_common_lnx-3.6-and-newer-pak.zip (1C was superseded by 1D)

If successfully installed, when the USB device (04e2:1420 Exar Corp.) is connected it the device node /dev/ttyXRUSB0 should show up.

Bill of Materials

Name Part
U2 MaxLinear SP339ECR1-L
U3 MaxLinear XR21B1420IL28-F

Online Resources

Exar XR21B1420IL28-0A-EVB Evaluation Board User’s Manual Rev 1A

Exar XR21B1420/21 Evaluation Board Schematic Rev 1.0

MaxLinear XR21B1420 Datasheet

MaxLinear SP339E Datasheet

XR21B1420 - MaxLinear

Exar XR21B1420IL28-0A-EVB Evaluation Board User’s Manual Rev 1A

Exar XR21B1420/21 Evaluation Board Schematic Rev 1.0

Exar XR21B1420/21 Evaluation Board Schematic Rev 1.0

running Due at 1Mbaud and 2.5M baud [SOLVED] | AVR Freaks