Pololu Wixel Instrukcja Użytkownika Pobierz pdf (Strona 40)

Caveats

• If data is received on the ASCII_RX or BINARY_RX pins too quickly, it could result in the internal buffers

filling up and data loss. This app has 512 bytes of buffer space for the ASCII-to-binary conversion and 512 bytes

of buffer space for the binary-to-ASCII conversion.

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 maximum pin current 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

• Serial ASCII-to-Binary App v1.0 [http://www.pololu.com/file/download/serial-ascii-binary-v1.0.wxl?file_id=0J640]

(17k wxl), released 2013-06-06: Initial release.

9.e. Serial-to-I²C App

Overview

This app turns a Wixel into a serial-to-I²C bridge, acting as a master controller on a single-master I²C bus. To perform

I²C operations, another device can issue serial ASCII commands to the Wixel on its radio, UART, or USB interface.

I²C [http://en.wikipedia.org/wiki/I²C] is a two-wire interface that is commonly used for communications on peripherals

like the LSM303DLHC compass [http://www.pololu.com/product/2124] and the BMP085 pressure sensor

[http://www.pololu.com/product/1646]. The official specification [http://www.pololu.com/file/download/

UM10204.pdf?file_id=0J435] (371k pdf) for the I²C bus is published by NXP.

Installation Instructions

Download the Serial-to-I²C App (v1.0) [http://www.pololu.com/file/download/serial-i2c-v1.0.wxl?file_id=0J480] (26k wxl).

Open it with the Wixel Configuration Utility, choose your parameters, and then write it to a Wixel. See Section 4 for

more information on how this is done.

Default Pinout

Pin Function

P1_0 SCL I²C clock (0–3.3 V)

P1_1 SDA I²C data (0–3.3 V)

P1_6 TX transmits serial data (0–3.3 V)

P1_7 RX receives serial data (0–3.3 V)

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