After a few weeks of waiting, I’ve finally received two breakout boards with BMP085 barometric pressure sensors.
One of my first hardware projects for RPi were Serial Shield expansion boards. They provide easily accessible serial interfaces with voltage level conversion for interfacing with 5V logic and a battery backed-up RTC clock which enables hardware clock support in Raspbian.
UPDATE (2013-01-25): I’ve updated RPi firmware today and it seems that the latest kernel (3.6.11+) includes working driver for TL-WN725N. Instructions below are now obsolete/educational 😉
I’ve decided to replace TL-WN721N adapters with something smaller. After some research and tests with my old Debian laptop, I’ve bought two TP-LINK TL-WN725N 802.11n USB adapters.
In contrast to 721’s, they are smaller and are built on different chipset – Realtek RTL8188CUS.
Installation is not as easy as with Atheros-based adapters, because no kernel driver supports this chipset. Fortunately, Realtek provides open-source Linux drivers on their website.
So, let’s get started 🙂
My Raspberries are expanded with DS3231 I2C realtime clock. It’s a very simple solution, as only required external component is a backup battery (crystal is integrated into the chip!). And it’s also claimed to be very accurate 🙂
By default, Raspbian installation uses “fake hwclock” to read previously stored date/time from file just before clock is synced by NTP client. We’re going to switch to “full” hwclock, first ensuring that our RTC is seen by kernel.
Here’s a short tutorial on how to quickly setup WiFi on your RasPi.
I’m using Atheros based TP-LINK TL-WN721N USB adapter – good and cheap.