Having had a chat with a number of people about my previous LEA based NTPi board here http://ava.upuaut.net/?p=581 a few things were apparent. Firstly designing a board to fit a Pi you’ve removed the composite header from was silly and not checking it on a stock Pi the board results in it not fitting. Secondly the LEA based board is probably more complex that most people need for a Pi based NTP server.
The new positioning modules from Ublox the MAX-7 series are cost effective high performance and provide the PPS output needed for accurate time keeping. I set about designing a simpler board around the MAX-7Q module.
The MAX-7Q positioning module features a RTC Crystal, very low power usage and high performance. Although not a true timing module it is more than adequate for a Pi based NTP Server. Its worth noting the module can, with a serial command, be placed in “Stationary” dynamic mode which is the default mode for the much more expensive timing modules.
Also of note is the PPS output can be, again with serial commands, be increased to an output of up to 10Mhz for other applications.
To keep the board simple it just features the MAX-7Q, a Raspberry Pi header, battery, power and PPS LED’s and provision for an SMA connected active patch antenna (puck) :
The MAX-7Q is connected via serial to the Pi and the PPS is connected to GPIO18 (pin 12). The design is such that it should fit in a case (I’ve only tested it in the Multicomp MC-RP001). The Pi GPIO’s are passed through to an unpopulated header should you wish to connect other items to the Pi. When in place the antenna cable exits between the USB and RJ45 connectors :
Resulting in a nice tidy NTP Server. The made up boards supplied with a CR2032 battery can be purchased from HAB Supplies here http://ava.upuaut.net/store/index.php?route=product/product&path=59_60&product_id=95
I haven’t intended this board to be used in Pi powered HAB stuff due to the way the Pi interfaces with radio the GPS needs to connect via I2C. This board connects the GPS via serial so please bear that in mind.
I also took the opportunity to fix the design fault with the LEA eval board and can also supply these with LEA-6T timing modules or LEA-5S modules as needed. The LEA eval board is designed as more of a multipurpose board featuring PPS and (where LEA-6T fitted) PPS2 outputs. SMA or u.FL inputs. USB to connect to a PC, Pi header to connect to a Pi, generic header for other uses. Board can be powered by header, USB or Pi header. The board does fit in a Pi case but its tight and the antenna exits over the HDMI :