USB interface for HRPT decoder

Note: decoder needs to be set to "6x2" mode.

wsat verion 2010.01 can communicate via this interface with the decoder.

pin left on schematicconnect?description
+5VdependsSee chapter 'Power'
ctrl[7:0]Only if channel selection neededsee chapter "Selection channels etc."
(no text, from RD of FT245R)Not if no channel selection neededTBD
DIO[7:0]Yessee table 1
is_outOnly if channel selection neededTDB; connect to pin 63 buffer-FPGA = pin 14 par. port connector
rd_offIf NO channel selection: to +5Vsee chapter "Selection channels
clkYessee table 1
readynYessee table 1
r_clk_nYessee table 1

HRPT-data from decoder to USB.

Next table shows which connections are needed to transfer the HRPT-data via USB to PC. If possible existing connectors on the decoder PCB are used. In a few occasions a connection needs to be made directly to a FPGA pin. Be aware that the ecoder PCB contains 2 FPGA's. The one near the EPROM contains the actual decoder; the other FPGA contains the data-buffer. This is the one to connect to the USB-interface. Naming in the left column of tables below means:
13@FPGA means: pin 13 of buffer-FPGA
17@CONP means: pin 17 of connector near parallelport
3@CON10 means: pin 3 of connector CON10
Tabel 1: Connection decoder with USB-interface: Data from decoder to USB.
13@FPGA r_clk_n lees-klok
17@CONP readyn 0=data in decoder
59@FPGA D0 HRPT-data
3@CON10 D1 HRPT-data
2@CON10 D2 HRPT-data
1@CON10 D3 HRPT-data
3@CON9 D4 HRPT-data
1@CON9 D5 HRPT-data
3@CONP D7 (!! See note below!!) !!!Via R=100 ohm!!!
9@EPROM clk 666/1300 kHz
NOTE: Use fixed wsat release 2010.01.a.
For earlier release 2010.01, "3@CONP" needs to be connected to "D6" instead of "D7".
Table 2: Connections in decoder
decoder-PCB Connect with description
69@FPGA GND set to 2x6 mode
2@CON9 3@CONP connect r_clk with rdy_nib

Selection channels etc.

If channel selection/decoderselection isn't needed via PC then this part can be kept very simple. In fig. 1 IC 74273 isn't needed, and pin "rd_off" must be connected to +5V. This prevents that the USB chip will drive the data lines. For further adaptions see table 3.

Tabel 3: No channel selection by PC (all channels active)
decoder-PCB Connect with Description
18@CONP GND output always active
1...6 @CON1 to +5V all channels active
jumper CON2 pin1-2 remove manual selection 'on'


There are a few possiblilities to power USB-interface and decoder with +5V. The USB-connector contains 5V, from PC, which can be used to power both interface and decoder. As a result the decoder is always powered if PC is on (and decoder is connected to PC).
Possibilities are:
power to do comments
Power USB-interface and decoder from USB Add jumper J1 (fig. 1)
Remove jumper J3 (fig. 1)
Connect 5V-pin to 5V decoder
Don't connect an external power unit to decoder!
Disadvantage: decoder altijd On if PC is on.
Power USB-interface and decoder from decoder Remove jumper J1 (fig. 1)
Add jumper J3 (fig. 1)
Connect 5V-pin to 5V decoder
Use power unit decoder
Power USB-interface from USB connector
Power decoder using it's own power unit
Add jumper J1 (fig. 1)
Remove jumper J3 (fig. 1)
Disadvantage: "false" currents if decoder is powerd and USB not or vice versa

About last possibility: The "false currents" go via the connections between USB-interface and decoder. As a result decoder-LEDs may go 'On' while decoder isn't powered. It is possible that after some time decoder and/or USB chip will degrade.