StrichLux/CORE

The StrichLux Core is the "motherboard" of the system, that holds the framebuffers and lets the I/O modules talk to each other. It also holds the "transform engine", which is the FPGA that can do various transforms between the input and output.

Next Troubleshooting Steps

• Sometimes chanbuf_clken_req is not asserted during a READ cycle
  • Checked if rx_ready is asserted next, found that it was asserted at the wrong time
  • Found that bit_nbr was getting reset mid-byte sometimes
    • Very brief glitches on nSS were causing this
      • Implemented a stability filter into this signal in the SPI module
  • Now i'm not seeing "sliding bits" in the output, but sometimes it hangs and never changes again
    • Realized on the way home that nSS is fed directly into the module controller to reset the cmd, so glitches would now cause this!
      • Next time: Make the SPI controller output the nss_risen_stable signal and use that in the module controller

Project Log

• 2013-05: On hold for how due to too many other paying/deadlined projects. Will resume when working on invisibleMaze.
• 2012-07-02: Fixed one issue with the SPI controller sometimes resetting state on brief nSS glitches, but still having issues. More troubleshooting tomorrow.
• 2012-07-02: READ logic in place but failing sometimes. More troubleshooting tomorrow.
• 2012-06-18: Worked through a bunch of logic issues, now the WRITE command seems to work, and READ returns the address pointer as it should at this point. Real READ logic is next on the list to implement.
• 2012-06-16: Finished assembly, found an issue with the DC-DCs and solved it. Got the FPGA programming, but having some logic issues with getting the SPI going.
• 2012-06-15: 80% done assembling the first board.
• 2012-06-10: Started writing firmware, basic structure is in place and input module controller is 80% ready with very basic functionality (only WRITE command supported).
• 2012-05-27: Ordered boards from MyRO PCB. Parts are here already.
• 2012-05-26: Waiting to get PWR-DC5 and IO-ETH boards done to send all 3 off to get made at once.
• 2012-05-23: Found the power switch would interfere with the power jack, replaced with a vertical switch to resolve this issue.
• 2012-05-20: Routing complete, will wait to send board so I can review it again tomorrow.
• 2012-05-15: Routing continues, 30 airwires to go.
• 2012-05-08: EAGLE purchase went through, board routing started.
• 2012-05-07: Ran checklist, completed last few changes. Rev. 1 schematic complete, board layout started (but stuck until my EAGLE purchase goes through, as the board is 160x100mm).
• 2012-05-06: Schematic complete, checklist still needs to be run.
• 2012-05-05: Started working on the schematic.
• 2012-05-04: Started putting together specs/BOM.

Project Ideas

• Required I/O
  • 4 Input modules (one SPI slave transceiver and one I2C master transceiver each)
  • 4 output modules (one SPI slave transceiver and one I2C master transceiver each)
  • RS232 and USB for troubleshooting and configuring the core board itself
  • 1 Power module (one I2C master transceiver)
• Local framebuffer memory
  • Dual-port memory would be best so the output and input sections can both deal with it independently
  • 8 bits per frame * 512 channels per universe * 4 universes = 16kbit (2kbyte) of framebuffer memory required
    • Twice that for double-buffering would be awesome, so 32kbit/4kbyte of dual-port memory wanted
  • Split into 4 channels, so each block would be 8kbit/1kbyte
  • Reading/writing needs to happen in parallel for each block
• Looking at using the LFXP2-8E-5TN144C FPGA
  • 5 series is ~$5 cheaper but only has 3 sysDSP blocks, given the 4 channel system, 4 blocks seems a better fit

Revision 1 Issues

• Resistor packs for status LEDs are wrong footprint
• Power Module connector footprint needs tweaking to move pads further apart, solder bridges under the connector are almost impossible to avoid as it is
• Schematic lists ferrite chips as L1-L4, BOM as FB1-FB4
• Adjust resistor on the two DC-DC converters needs to go to GND not VOUT