Badger2

Badger2

Badger2 will be a hybrid of the RocketBoard1 and the BadgerCub. It will be based around the LPC2368 as tested on RocketBoard1 and will use the Venus GPS chipset and TI CC1111 (or CC1110) as used on the BadgerCub. It will also provide a place to mount a Gumstix Overo for more intensive processing tasks e.g. interfacing to the software GPS front-end.

Sensors

• SCP1000 Absolute pressure sensor
• IDG650, IDZ650 3-Axis Gyro Pair
• AD7927 ADC to interface gyros
• LIS3LV 3-Axis Accelerometer
• HMC5843 3-Axis Magnetometer
• ADIS16204 2-Axis High-g Accelerometer (for rocket thrust measurements)
• Venus634 10Hz GPS chipset
• SiGe SE4120 Software GPS Front-end
• CC1111 based radio transceiver.

Rev 1 Issues

• TCXO package upside-down
• GPS VBAT backup line on internal layer / ground via
• 1.8V Reg package - tab is not GND
• Via by 3.3V reg to GND - actually looks like this is for the large pyro reservoir cap
• GPS LED wrong way round on schematic
• Venus GPS RF ground tracks are a bit odd - make a proper split ground plane
• Radio LED and resistor tracks crossing
• Check for overlapping tracks and clearance issues highlighted by DRC (i.e. by pyro channel 1 and on one of the SD card data lines)
• Space capacitors next to SiGe and resistors by the Venus for easier oven reflowing (they tend to try and stick together)
• SPI resistor with one end not connected to anything
• SPI connector has one pin not connected to anything, probably should be ground.
• AD16204 has the lower range Y-axis aligned with rocket thrust vector. Rotate 90 degrees for Rev 2.
• Tactile switch footprint could be a smidge wider.
• Duplicate decoupling capacitor on bottom of board.

Some useful things to include in future revisions:

• Reverse supply protection diode!!
• Switch mode supply
• CC1111 reset line going to LPC.
• Maybe make the JTAG connector be a small 1.27mm pitch connector like the CC1111.
• Some kind of supply voltage measurement, and possibly supply current monitoring?
• Make the pyro connector holes a bit bigger to fit the bad-ass orange connectors.
• Tent Vias
• Maybe change to a different high-g accelerometer as this one is a bit expensive.
• More pyro channels?
• Possibly higher resistance on pyro continuity test
• Break out spare analog channels and maybe connect the unamplified range of the gyros to the ADC too. Possibly two ADCs on the board?

Construction Notes

• Reset tactile switches (Farnell 1656434) don't seem to like being in the oven. Solder by hand.
• Venus also very heat sensitive, can go in the oven but doesn't like multiple cookings very much. Hot air soldering it is a PITA.

CC1111

The CC1111 has its own page with information about wrangling this chip into doing our evil bidding. The code is under CC1111_firmware and can be compiled by SDCC. It simply takes commands on its UART from the LPC and transmits or receives strings on the radio. The CC1111 shall flash its LED thrice upon power-up.

The CC1111 will send a ':' character indicating it is ready to receive a command. The LPC should respond when ready with a single character to specify which command it wants. After that the LPC may need to send or receive a parameter or some data depending on the command.

Commands

• T - Transmit a string on the radio. After issuing this command the LPC should send a null terminated string for the CC1111 to transmit. When the string has finished being sent then the CC1111 will reply with a ':' signifying it is ready for another command.
• R - Switches the CC1111 into receive mode and will wait for the ground station to uplink a string. If a string is received then the CC1111 will send it on to the LPC as a null terminated string. Otherwise, if the receive times out then just a null character to the LPC.
• B - Accepts a baud rate as an ASCII null-terminated string and changes the radio transmit baud rate.
• D - Returns the CC1111 internal temperature as a ASCII string formatted float.