MaxLinear XR21B1420IL28-0A-EVB USB to RS-232/422/485 Evaluation Board
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.
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:
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xr_usb_serial_common_lnx-3.6-and-newer-pak.zip (1C was superseded by 1D)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
Exar XR21B1420IL28-0A-EVB Evaluation Board User’s Manual Rev 1A
Exar XR21B1420/21 Evaluation Board Schematic Rev 1.0