StopWatch

This is a simple demo of CLaSH tool for Haskell compilation to .vhdl.

Uses one algebraic datatype, and two types of counters as Mealy machines.

Displays seconds since reset on a seven segment display.

Important files:

• DigitalClock.hs - contains Haskell code.

• TopEntity.vhd - contains wrapper that translates signal names in VHDL generated from Haskell to Papillio LogicStart pin codes.

• constraints.ucf - maps descriptive pin codes to FPGA's pin numbers.

• SevenSeg.xise and SevenSeg.gise - Xilinx ISE project.

Recompilation

Not all steps are automated yet, so you may need to do few steps to get it on your Papillio:

0. For simulation just compile it with clash as a Haskell program, and run.

1. For VHDL generation:

   • run interpreter: clash --interactive DigitalClock.hs
   • enter :vhdl in the interpreter to generate .vhdl code

2. Refresh Xilinx ISE project by:

   • removing all previously generated .vhdl files: rm -rf xst/ DigitalClock/*.vhdl
   • clicking on ISE - it will ask you to remove files from the project, mark checkbox yes.
   • copy new VHDL files: cp -r vhdl/DigitalClock/*.vhdl DigitalClock/
   • re-add these files as source files in Xilinx ISE (right click within project window)

3. Recompile Xilinx ISE project and generate new bitcode file SevenSeg.bit.

   • If there are any errors, compare type of recordish in TopEntity.vhd wrapper file, and generated DigitalClock/topEntity_0.vhdl file. Modify the name of the datatype accordingly in two selectors just below.
   • Make sure the toolchain follows all the steps until generation of code for the target device. (Note that for a different device you may just provide different constraints.ucf file to ISE, since this file maps VHDL signal names to FPGA pins.)

4. Upload the bitcode onto your FPGA device: papillio-prog -f SevenSeg.bit