5 This is a photo of our original board with serial port for off-board GPS,
6 without the big off-board 1000uF cap from the original ejection circuit. All
7 v0.2 boards were hand-assembled by Bdale.
9 <a href="v0.1/loadedpair.jpg"> <img src="v0.1/loadedpair-thumb.jpg"></a>
12 significantly different than later versions, in both mechanical and
15 * 2.5 x 1 inch board with all parts mounted on one side
16 * 4-pin PicoBlade serial port connector for attachment of external GPS module
17 * USB connector projected approximately 3mm over the edge of the board
18 * Debug connector used 4 IC socket pins on 100 mil centers
19 * 50ma LDO regulator on early boards, later boards used a 100ma part
20 * [Microchip 25LC1024](http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en520389) CMOS serial EEPROM instead of DataFlash
23 * [Microchip MCP9700A](http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en027103) discrete temperature sensor
24 * used 1000uF electrolytic capacitor charged to 5V for pyro supply
25 * a dual LED instead of just one attached to the CPU
27 The v0.1 artwork had three issues, two of which required physical rework
28 on each board, all of which were fixed in v0.2.
30 * The USB connector footprint was placed wrong, so that the
31 connector hung out over the edge of the board instead of being
33 * We needed chip select on the SPI memory. To fix that, we gave up the
34 ability to put the accelerometer into self-test mode and used that
35 GPIO line to pull chip select on the memory, which required two
37 * The igniter sense circuits each needed a second resistor to
38 complete the voltage divider so our 3.3V CPU ADC could read the
39 5V ejection voltage. This was fixed by changing two resistor
40 values, and tacking two additional resistors onto the board
41 with jumpers to ground.
43 The schematics and PCB artwork for this version as of the working-v0.1 tag
44 are available here as pdf copies for easy reference:
46 * [schematic](v0.1/telemetrum.pdf)
47 * [pcb artwork](v0.1/telemetrum.pcb.pdf)
48 * [bill of materials](v0.1/telemetrum.bom)
52 These are photos of our second version. All v0.2 boards were hand assembled
55 <a href="v0.2/cimg5164-cropped.jpg"> <img src="v0.2/cimg5164-thumb.jpg"></a>
56 <a href="v0.2/cimg5171-cropped.jpg"> <img src="v0.2/cimg5171-thumb.jpg"></a>
58 Lots of things were different from v0.1. Perhaps the biggest change was
59 integrating a Venus GPS receiver and a passive patch GPS antenna. This
60 required stretching the board length to 2.75 inches, and changing the layout
61 to put through-hole parts on the opposite side from
62 the surface mount parts. While we were at it, things were rearranged to put
63 tall parts near the center and not on the board edges so that boards could
64 be mounted in smaller diameter tubes.
66 Another significant change was adding a "companion" port, intended to support
67 expansion boards but also possible to use as a programming interface. With
68 a suitable cable, the presence of the companion port allowed any TeleMetrum
69 board to be used to re-program any other TeleMetrum or TeleDongle
70 board. Elimination of the discrete temperature sensor and second LED were
71 necessary to free up the pins needed for the companion interface.
73 We also changed to a different flash memory chip with 1 megabyte of storage.
75 Issues with the v0.2 boards included:
77 * The passive GPS antenna turned out to have disappointing performance due
78 to our many PCB geometry constraints.
79 * The initial voltage regulator on v0.2 boards was a 100mA part. Once we
80 realized how much power the GPS receiver needed to achieve initial lock,
81 we switched to a 150mA part.
82 * The reset circuit worked well for the cc1111 but was marginal for the GPS
83 chip .. sometimes the board would have to be power cycled several times
84 to get the GPS to come up correctly.
86 The schematics and PCB artwork for this version are on the v0.2 branch in
87 our git repository, here are pdf copies for easy reference:
89 * [schematic](v0.2/telemetrum.pdf)
90 * [pcb artwork](v0.2/telemetrum.pcb.pdf)
91 * [bill of materials](v0.2/partslist.csv)
95 These are photos of our third version, which was our first production
96 build. By the time we understood what we wanted to change in v0.2, things
98 well enough that every time we went to a launch someone would ask about
99 buying boards from us. So in January 2010, Keith and Bdale made the decision
100 to produce enough boards to sell some to others. These were sold between April
101 and December 2010, and performed very well.
103 <a href="v1.0/cimg5972-crop.jpg"> <img src="v1.0/cimg5972-thumb.jpg"></a>
104 <a href="v1.0/cimg5974-crop.jpg"> <img src="v1.0/cimg5974-thumb.jpg"></a>
106 The changes from v0.2 were fairly small. The value of the reset capacitor
107 changed to increase the probability of the GPS chip coming up correctly, and
108 we moved to using a Taoglas amplified patch antenna attached to the U.FL
109 connector instead of the passive GPS patch antennas.
111 There were really only two issues with the v1.0 boards that annoyed us. The
113 that the reset circuit still wasn't satisfying. The GPS chip would sometimes
114 fail to initialize, particularly in hot weather. The second was that
115 fluctuation of the 3.3 volt power rail correlated with radio transmission
116 induced noise patterns in the accelerometer data.
118 The schematics and PCB artwork for this version are on the v1.0 branch in
119 our git repository, here are pdf copies for easy reference:
121 * [schematic](v1.0/telemetrum.pdf)
122 * [pcb artwork](v1.0/telemetrum.pcb.pdf)
123 * [bill of materials](v1.0/partslist.csv)
127 These are photos of v1.1, which rightfully looks very similar to v1.0. These
128 boards were sold through most of 2011.
130 <a href="v1.1/telemetrum-v1.1-thside.jpg"> <img src="v1.1/telemetrum-v1.1-thside-thumb.jpg"></a>
131 <a href="v1.1/telemetrum-v1.1-smtside.jpg"> <img src="v1.1/telemetrum-v1.1-smtside-thumb.jpg"></a>
133 There were several changes in v1.1:
135 * different flash memory part due to supplier availability problems. It turned
136 out that 2 megabyte chips were cheaper than 1 megabyte, so the size doubled.
137 * updated reset circuit to improve reliability at temperature extremes
138 * changed the GPS antenna footprint to eliminate the large through-hole
139 originally intended for use with a passive patch
140 * irq line eliminated from the companion port
141 * an additional resistor divider added to allow sampling the 5V supply
143 With an associated software change, being able to sample the 5V and 3.3V rails
144 made it possible to factor out almost all of the coherent noise from the
145 accelerometer data seen with v1.0 boards.
147 The one big problem with v1.1 boards turned out to be that they would
148 sometimes reset during flight, usually when firing pyro charges. Bdale
149 wrote a [blog entry](http://www.gag.com/bdale/blog/posts/RF_Immunity.html)
150 that explains in some detail what we finally learned was causing this.
152 For those who don't have ready access to the gEDA suite, here are pdf snapshots
153 of the files for Production PCB version 1.1 in more easily readable form.
155 * [schematic](v1.1/telemetrum.pdf)
156 * [pcb artwork](v1.1/telemetrum.pcb.pdf)
157 * [bill of materials](v1.1/partslist.csv)
161 This is our current production version, first made available for sale on
164 Changes from v1.1 include:
166 * changed to 70g accelerometer from Analog Devices since Freescale MEMS parts
167 are still unavailable following the Japanese earthquake and tsunami.
168 * reset controller changed from 3.15 to 3.00 volt trip point
169 * bypass cap added to LDO input
170 * pyro circuit resistor values tweaked to eliminate a glitch that at least in
171 theory made it possible for pyro charges to fire at power on. We never saw
172 a problem, but the change was easy and obvious.
projects / web / altusmetrum / blob