RS485/GPIO Shield for Raspberry Pi

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Contents

Introduction

This is a shield to add a RS485 level shift to the UART of Raspberry Pi. Moreover, it also breakout the rest headers for easy access.

RS485 RPI 1.jpg

Schematics

Schematic

Tutorial

The UART on Raspberry Pi is on P1 and shown below:



RPI UART.png


The UART is /dev/ttyAMAO, it defaults to output system log. But if user wants to use this UART to connect to other modules through UART, for example, GPS module, we need to change the configuration.

The detailed steps are as following:

We need to modify two files: /boot/cmdline.txt and /etc/inittab.

Modify /boot/cmdline.txt:

Replace the original content:

dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait

With:

dwc_otg.lpm_enable=0 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait


Modify /etc/inittab:

Comment out the last line of /etc/inittab. To comment out, it simply addess a '#'.


$ sudo vi /etc/inittab

  1. T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100

Save the changes, and reboot. We will get an UART with baud rate of 115200.

Resources

How to buy

Here to buy RS485/GPIO Shield for Raspberry Pi on store

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