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[web/altusmetrum] / TeleMetrum / index.mdwn

diff --git a/TeleMetrum/index.mdwn b/TeleMetrum/index.mdwn
index 93550e393d8e28080d8f34d928f12fff6ed79777..d5ed480c36fb2af66cbb491b0ab890dd80a651ca 100644 (file)
--- a/TeleMetrum/index.mdwn
+++ b/TeleMetrum/index.mdwn
@@ -98,10 +98,14 @@ always want GPS on board, which lead to our current second generation boards.
 * [Microchip 25LC1024](http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en520389) CMOS serial EEPROM instead of DataFlash
        * 128k x 8
        * SPI interface
-* [Microchip MCP9700A](http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en027103) temperature sensor instead of using cc1111 on-chip sensor
-* used 1000uF electrolytic capacitor charged to 5V for pyro charges
+* [Microchip MCP9700A](http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en027103) discrete temperature sensor
+* used 1000uF electrolytic capacitor charged to 5V for pyro supply
+* two LEDs instead of one attached to CPU
 
-## [Production History](production) ##
+The elimination of the discrete temperature sensor and second LED were
+necessary to support the companion board interface added in v0.2.
+
+## [Production History](../production) ##
 
 ## [Flight Logs](flightlogs) ##
 
@@ -114,18 +118,27 @@ always want GPS on board, which lead to our current second generation boards.
   place parts!  Without an inspection microscope, loading and testing these
   boards might be impossible.
 
-* The v0.1 artwork has the USB connector footprint placed wrong, so that the
-  connector hangs out over the edge of the board instead of being flush with
-  the edge.
-
-* The v0.1 artwork has two issues that require cuts and jumps.  The first is
-  that we need chip select on the SPI memory.  To fix that, we give up the 
-  ability to put the accelerometer into self-test mode and use that GPIO line
-  to pull chip select on the memory.  The second is that the igniter sense
-  circuits each need a second resistor to complete the voltage divider so our
-  3.3V CPU ADC can read the 5V ejection voltage.  This is fixed by changing
-  two resistor values, and tacking two additional resistors onto the board
-  with jumpers to ground.
+* The addition of on-board GPS in v0.2 means that the total power consumption
+  can exceed the rate at which we draw power from the USB interface, 
+  particularly when the GPS is in cold start mode.  This means a battery must 
+  be attached during operation, and also that the battery will only charge 
+  effectively from USB when the board is turned off.
+
+* The v0.1 artwork had three issues, two of which required physical rework
+  on each board.  All of these issues were fixed in v0.2.
+
+       * The USB connector footprint was placed wrong, so that the
+         connector hung out over the edge of the board instead of being 
+         flush.
+       * We needed chip select on the SPI memory.  To fix that, we gave up the 
+         ability to put the accelerometer into self-test mode and used that 
+         GPIO line to pull chip select on the memory, which required two
+         cuts and two jumpers.  
+       * The igniter sense circuits each needed a second resistor to 
+         complete the voltage divider so our 3.3V CPU ADC could read the 
+         5V ejection voltage.  This was fixed by changing two resistor 
+         values, and tacking two additional resistors onto the board
+         with jumpers to ground.
 
 ## Artifacts ##