- can I put the GPS chip antenna on the board *and* allow for an SMA or other
connector if we want it off-board?
+- changing the memory part from the SOIJ8 to the DFN8 would save about 2mm
+ in width, but that doesn't really help.
+- changing the 5V switcher from S8 to MS8 takes us from 5 tall to 3 tall, but
+ costs $0.30 more per piece and isn't stocked by Digikey. Not worth it?
+
+- noticed the NXP SC18IS600, which is an SPI slave to I2C master interface
+ with a few GPIO lines... mate that with an HMC5843, which is a 3-axis
+ magnetic sensor, and we might have another interesting companion board for TM
+
+
- To Do List
- add serial connector back to schematic as optionally loaded part
- move USB connector on PCB layout 80 mils in from board edge
- - create PCB footprints for the GPS module and GPS antenna
+ - move yellow LED and passives closer to LiPo connector
+ + create PCB footprint for the GPS module
+ + create PCB footprint for the GPS antenna
+
+
+2009.10.09
+- flew lots of stuff last weekend at O'fest. 100g accel worked ok in G-Spot,
+ broke beeper presumably on landing with tangled chute. board seems ok
+ otherwise, need to verify that baro sensor is still ok.
+
+- put out sample requests for gps passive patches from 3 vendors
+
+- when adding GPS, let's plan for passive patch loaded on the back of the
+ board, plus a U.FL connector loaded on the top of the board with DC bias feed
+ to support external active antennas. This probably means passive patch
+ direct to gps chip, then a dc blocking cap, a chip inductor for dc bias
+ injection, and the connector. A suitable connector is:
+
+ WM5587CT-ND Molex 73412-0110 0.70 in single quantity
+
+ Keith found gps active antennas with cable to U.FL connectors and Molex sells
+ cables with U.FL to bare leads, so this should cover the bases.
+
+- TelePyro doesn't really need a CPU. How about an SPI to I2C converter chip
+ with GPIO lines and an I2C ADC chip? Cheaper and easier than a PIC?
+
+ PIC16F882 in SSOP-28 is $2.10 per, 1.41 @ 25 units
+ -- PIC16F883 is $2.12, PIC16F886 is $2.32, have better memories
+ CP2120 in QFN-20 is $2.41 per, 2.27 @ 25 units
+
+ The Silabs CP2120 has 8 gpio lines but is only available in QFN20. The NXP
+ part I discovered earlier, the SC18IS600, has 4 full gpio lines and 2 lame-o
+ pins, but is available in a hand-solderable version. Add in a Maxim ADC,
+ and something like this emerges:
+
+ DigiKey 568-3232-5-ND NXP SC18IS600IPW,112 2.25
+ DigiKey MAX11603EEE+-ND Maxim MAX11603EEE+ 4.00
+ Mouser 595-CD4508BM TI CD4508BM 1.70
+
+ The 4508 has separate reset inputs and latch controls for each 4-bit latch.
+ The reset forces all outputs low, and the reset is an active-high input.
+
+ The NXP part has an active-low reset input, with 10-30k internal pullup.
+
+ The ADC has no distinct reset input.
+
+ A suitable SOT-23-5 reset controller is the MCP1319MT-29LE... it has a master
+ reset input we can ignore, and both active high and active low reset outputs.
+
+ DigiKey MCP1319MT-29LE/OTCT-ND 0.70
+
+ This plus 8 copies of the pyro circuit on TM (FET and 4 resistors) and we're
+ good to go.
+
+ Wonder if there are resistor networks it'd be worth trying to use to ease
+ component placement? Yes... these are 8 x 0402, more or less:
+
+ 100 ohm 741X163101JPCT-ND 0.16
+ 10k 741X163103JPCT-ND 0.16
+ 27k Y1273CT-ND 0.18
+ 100k Y1104CT-ND 0.18
+
+- another way to think about all this is that I could panelize a set of boards
+ all done in 2 layers, then treat that as a sub-panel I put N copies down of
+ to fill up a 33each.com max panel size.
+2009.10.16
+- move to AT45DB161D 16-megabit SPI "DataFlash" EEPROM from Atmel?
+ AT45DB161D-SU-ND in SOIC-8 for $2.26 each
+ appears to compare favorably against $4.40 for current 128kx8 part
+ minor concern about write power, but probably red herring
projects / hw / telemetrum / blobdiff