The Amp Hour

An Interview with Craig J Bishop


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Welcome, Craig J Bishop!

  • Craig designed and built the Gameslab, which is a custom gaming platform built with a Xilinx Zynq part (XC7Z035). (Update: Craig has been posting more about the Gameslab on his site here)
  • Bought reballed chips on PCBs. They were actually a $1200 chip he got for $80.
  • Episode with Ryan Cousins
  • There is apparently a kit for counterfeiting Xilinx chips
  • National lab has a pdf on how to detect counterfeits
  • Digilent Zybo
  • Craig built the board on the JLC 6 layer process at 210x100 for each board. $150 for 5 PCBs.
  • DDR3 chip was .8mm pitch
  • Using stack up to calculate impedance/prop delay
  • Used an excel sheet to track delay and skew for nets, since KiCad can't track delays between layers
  • FPGA on chip delays are also stated in the datasheet and need to be accounted for.
  • Running Rust on STM32L0, on kernel modules in A9, applications / games
  • Sense resistors with instrumentation amps going to the ADC to measure each rail's current draw.
  • BQ24250 chip for charging with configurable registers
  • Zynq doesn't necessarily need the bitstream programmed first. Instead the A9s boot first and can load the bitstream.
  • Every game brings its own hardware
  • Can put the Gameboy hardware into the fabric!
  • Craig doesn't like verilog, so he uses a higher level language called SpinalHDL. It is a fork of Chisel, which is based on Scala.
  • Each of the above languages are strongly typed. Loosely typed means you can convert between data types, like in C.
  • "Verilog is becoming the assembly language of FPGAs"
  • ZipCPU
  • AXI bus
  • Most designs need to reimplement different hardware blocks. But there are libraries in Chisel, which can implement things easier.
  • Vex Risc V
  • Created a frame buffer for the LCD and some 2d graphics acceleration on the Gameslab.
  • Learned to program to make PC games. This was part of the idea behind the Gamesphere project as well.
  • PIC18F452 in a 40 pin DIP
  • Used AT91R4000 for the game sphere
  • Andrei LaMothe wrote the book "The Black Art of video game console design"
  • Cypress dual port SRAM
  • Craig's first "big boy job" was working for a a neighbor up the street starting a semiconductor packaging company (Tim Olson)
  • Deca Technologies was opening a Wafer Level Chip Scale packaging fab in the Philippines.
  • After iphone came out, there was a lot of demand for low profile complex chips.
  • Raspberry Pi photon problem
  • Added a "squishy" layer to the silicon, and then exposing certain parts of the silicon to the interconnect.
  • The graphics problem was that they wanted to make the chip bigger but the silicon smaller
  • EWLB from Infineon looks like a plastic wafer.
  • Can put two chips next to each other
  • There was a paper about the subject (has the image Chris and Craig were discussing during recording).
  • Sometimes the parts are placed 30 microns to the left, which is not good for the substrate they are placed upon.
  • Can get really expensive PnP machines but they go slow.
  • The microscope would spit out X, Y and rotation, but it scales with chip complexity, such as when there are two chips.
  • Needed to do traces between them
  • Craig's job was to take the output and do some autorouting between them.
  • Feature sizes were 1 micron
  • Package design looks like PCB design
  • Cadence sells System in Package designer but is really Allegro with different plugins.
  • Can people do their own SIP?
  • Craig thinks that design will move towards more SIP
  • Split die architecture
  • Split it into a few pieces: This will help improve yield and flexibility, as well as modularity.
  • Chris asked about Chiplets, a topic that is championed by Dr Subu (sp?)
  • Chiplets are going to do interconnect in silicon, not plastic
  • Example is BLE and micro
  • Adaptive alignment
  • Craig gave a talk at KiCon about how Autorouters work and how they have been improving.
  • Not your grandpa's autorouter
  • Freerouting is nice and available but it's not the latest
  • TopoR
  • Moving towards interactive design (P&R), but Craig thinks it should go the other way.
  • Generative design would be better
  • Dave Vandenbout's SKiDL talk
  • Craig was briefly interviewed by Piotr and Alvaro at KiCon
  • Find Craig on his personal site where he is documenting his projects (craigjb.com) and also find him as @craig_jbishop on Twitter.
  • Check out the Phoenix 3H (hardware happy hour) if you're in the area!
  • ...more
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    The Amp HourBy The Amp Hour (Chris Gammell and David L Jones)

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