= CW DOSI Probe for Cancer Monitoring

The proposed probe contains six pairs of LEDs, one photo-detector assembly and drive electronics.
Each of the 12 LEDs may be selected individually, with external drive current controlling the output intensity.

The LED pairs are arranged in a circle with a 25.4mm radius, with the photodiode assembly in the center.

A single flexible, multi-conductor cable provides power and control.  The HDMI cable seems like
a reasonable off-the-shelf solution (with mini-HDMI type C connector on the probe)

== Initial (Rigid PCB) Design
* Schematic: [http://ohm.bu.edu/~hazen/Roblyer/DC_Probe/cw_pcb_low_profile_sch.pdf PDF] [http://ohm.bu.edu/~hazen/Roblyer/DC_Probe/cw_pcb_low_profile.sch ExpressPCB]
* Layout: [http://ohm.bu.edu/~hazen/Roblyer/DC_Probe/cw_pcb_low_profile.pcb ExpressPCB]
* Parts list: [http://ohm.bu.edu/~hazen/Roblyer/DC_Probe/proto1_BOM.xlsx proto1_BOM.xlsx]

== Revised (Flex PCB) Design

* Second Layout
 * KiCAD (FINAL): [http://ohm.bu.edu/~hazen/Roblyer/DC_Probe/FlexV2/CWProbe2_Final.zip] (gerber files included)
 * Schematic (FINAL): [http://ohm.bu.edu/~hazen/Roblyer/DC_Probe/FlexV2/Probe2.pdf PDF]
 * Parts List (FINAL): [http://ohm.bu.edu/~hazen/Roblyer/DC_Probe/FlexV2/Probe2.xls XLS]
* Preliminary Layout
 * KiCAD (PREVIEW): [http://ohm.bu.edu/~hazen/Roblyer/DC_Probe/CWProbe.zip CWProbe.zip]
 * Gerbers (PREVIEW): [http://ohm.bu.edu/~hazen/Roblyer/DC_Probe/CWprobeV1.zip CWprobeV1.zip]
 * Schematic: [http://ohm.bu.edu/~hazen/Roblyer/DC_Probe/FlexV1/schematic.pdf schematic.pdf] -- Preview draft 2014-10-15
 * Layout: [http://ohm.bu.edu/~hazen/Roblyer/DC_Probe/FlexV1/top.png TOP] [http://ohm.bu.edu/~hazen/Roblyer/DC_Probe/FlexV1/bottom.png BOTTOM] -- Preview draft 2014-10-15
* Suggested parts:
 * Photodiode: [http://www.hamamatsu.com/resources/pdf/ssd/s5627-01_etc_kspd1025e06.pdf S4797] (Hamamatsu, low profile SMT)
 * LED 850nm: [http://www.roithner-laser.com/datasheets/led_div/smd/smt850-23.pdf smt850-23.pdf] (low profile SMT)
 * LED 750nm: [http://www.roithner-laser.com/datasheets/led_div/smd/smt750-23.pdf smt750-23.pdf] (low profile SMT)
 * [http://www.nxp.com/documents/data_sheet/74HC_HCT4514_CNV.pdf 74HC4514] decoder in [http://www.nxp.com/documents/outline_drawing/sot355-1_po.pdf TSSOP24] package (original)
 * [http://www.nxp.com/documents/data_sheet/74HC_HCT154.pdf 74HCT154] (Digi-Key 568-8858-1-ND) in VQFN 3.5mm x 5.5mm package (Alternative, see Note 1)
 * [http://www.diodes.com/datasheets/ds30937.pdf DMN2004DMK-7] dual N-channel MOSFET (Digi-Key DMN2004DMKDICT-ND)
 * [http://www.diodes.com/datasheets/ds30916.pdf DMP2004VK-7] dual P-channel MOSFET
 * uHDMI connector -- WM1280CT-ND	

Notes:

1.  The 74HCT154 is attractive because of the very small package, but has active-low logic outputs.  This requires a small change in the schematic.  The control interface should be unchanged.  Alternatively, the 4514 decoder is available in a TSSOP24 package which is about 7mm x 8mm


== Interface Cable

=== Proposed pinout for micro HDMI

|| '''Pin''' || '''HDMI Use''' || '''DOSI Use''' || '''Notes''' ||
|| 1 || Hot Plug Detect/HEAC- || || ||
|| 2 || Utility/HEAC+ ||  || ||
|| 3 || TMDS Data2+ || Photodiode+ || Photodiode Anode ||
|| 4 || TMDS Data2 || Photodiode GND || Shield for Photodiode signal ||
|| 5 || TMDS Data2- || Photodiode- || Photodiode Cathode ||
|| 6 || TMDS Data1+ || LED Power || Power for LEDs ||
|| 7 || TMDS Data1 Shield || AGND || Shield for LED power ||
|| 8 || TMDS Data1- || AGND || Ground for LEDs ||
|| 9 || TMDS Data0+ || A0 || Address 0 ||
|| 10 || TMDS Data0 Shield || DGND || Logic GND ||
|| 11 || TMDS Data0- || DGND || Logic GND ||
|| 12 || TMDS Clock+ || LE || Latch enable ||
|| 13 || TMDS Clock Shield || DGND || Logic GND ||
|| 14 || TMDS Clock- || DGND || Logic GND ||
|| 15 || CEC || A1 || Address 1 ||
|| 16 || DDC/CEC/HEAC Ground || DGND || Logic GND ||
|| 17 || SCL/DDC clock || A2 || Address 2 ||
|| 18 || SDA/DDC data || A3 || Address 3 ||
|| 19 || +5V power || VCC || Logic power (3.3V-5V) ||