Pololu Wixel User Manual download pdf (Page 36)

Caveats

Data will be lost if the Wixel receives bytes on the RX line faster than the radio can convey them to the other Wixel.

If you have trouble, try reducing the amount of data sent to the RX line by lowering the baud rate or adding delays to

your microcontroller’s code.

Caution: The Wixel’s I/O lines are not 5V tolerant. You must use level-shifters, diodes, or voltage dividers

to connect the Wixel to outputs from 5V systems. Also, avoid drawing more current from an I/O line than

it can provide (see the discussion of P1_0 and P1_1 in Section 1.a). Avoid connecting multiple output pins

together.

The Wixel does not support the RS-232 voltage levels typically used by DB9 serial ports. The Wixel’s I/O

lines, including the RX and TX lines, operate on voltages between 0 and 3.3 V. To connect the Wixel to an

RS-232 serial signal, you will need additional level-shifting and inverting hardware like the Pololu 23201a

serial adapter [http://www.pololu.com/product/126] (RS-232 serial is inverted; the Wixel’s serial interface

expects non-inverted serial).

Versions

• Wireless Serial App v1.3 [http://www.pololu.com/file/download/wireless-serial-v1.3.wxl?file_id=0J484] (26k wxl),

released 2011-06-20: Added the framing_error_ms parameter and the corresponding feature for disabling the

UART’s receiver after a framing error. Changed the behavior of the red and yellow LEDs; in previous versions

the red LED was off and the yellow LED simply indicated the presence of VIN power.

• Wireless Serial App v1.2 [http://www.pololu.com/file/download/wireless-serial-v1.2.wxl?file_id=0J468] (24k wxl),

released 2011-04-06: Added support for control signals. As a result, the radio protocol used is NOT compatible

with earlier versions. Also fixed a glitch on the TX line that occurred upon power-up or reset. Added blinking

behavior to the green LED to indicate USB data transfer.

• Wireless Serial App v1.1 [http://www.pololu.com/file/download/wireless-serial-v1.1.wxl?file_id=0J461] (18k wxl),

released 2011-03-23: Improved the radio protocol to fix a problem in v1.0 where if one Wixel resets but the other

Wixel does not, then (depending on the state of the other Wixel) there is a 50% probability that the next radio

packet sent in either direction will be ignored by the receiver.

• Wireless Serial App v1.0 [http://www.pololu.com/file/download/wireless-serial-v1.0.wxl?file_id=0J447] (18k wxl),

released 2011-03-22: Initial release.

Versions Configured for the Wixel Shield for Arduino

These are special versions of the app that have the same code as the corresponding standard versions, but have

different settings so that they will work well with the Wixel Shield for Arduino [http://www.pololu.com/product/

2500]. The default baud_rate was changed to 115200, which is the baud rate used by the Arduino Uno’s

[http://www.pololu.com/product/2191] bootloader. All the pin assignment parameters were set to -1 (disabled) except

arduino_DTR_pin, which was left at 0 (P0_0). The framing_error_ms parameter was set to 5. The only parameters

of these apps that can be modified by the user are the radio_channel parameter and baud_rate parameter. For

more information about configuring this version, please see the Section 2.c of the Wixel Shield User’s Guide

[http://www.pololu.com/docs/0J47].

• Wireless Serial App (version 1.3) configured for the Wixel Shield for Arduino [http://www.pololu.com/file/

download/wireless-serial-v1.3-shield.wxl?file_id=0J485] (25k wxl)

9. Wixel Apps Page 36 of 64

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Pololu Wixel User Manual Page 36