add a photo

[web/altusmetrum] / TeleMetrum / index.mdwn

diff --git a/TeleMetrum/index.mdwn b/TeleMetrum/index.mdwn
index a98fcac5a2a07bbdcbcff8fc96f7cc8e1a00a59a..d5ed480c36fb2af66cbb491b0ab890dd80a651ca 100644 (file)
--- a/TeleMetrum/index.mdwn
+++ b/TeleMetrum/index.mdwn
@@ -99,12 +99,13 @@ always want GPS on board, which lead to our current second generation boards.
        * 128k x 8
        * SPI interface
 * [Microchip MCP9700A](http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en027103) discrete temperature sensor
-       * eliminated in v0.2 to free GPIO line for companion interface
 * used 1000uF electrolytic capacitor charged to 5V for pyro supply
 * two LEDs instead of one attached to CPU
-       * eliminated second LED to free GPIO line for companion interface
 
-## [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) ##
 
@@ -117,17 +118,23 @@ 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 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
+       * 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 
+       * 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 
+       * 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