Quickstart guide¶

This guide provides instructions for preparing input for gerber2ems, using Antmicro’s open source SO-DIMM DDR5 Tester as an example.

Clone the board¶

git clone https://github.com/antmicro/sodimm-ddr5-tester.git
cd sodimm-ddr5-tester

Define nets to be sliced¶

The following sample traces were selected for the guide:

• /DDR5 SODIMM/A.CA0

• /DDR5 SODIMM/A.DQ1

• /FPGA MGT Interface/PCIE.CLK_P

• /FPGA MGT Interface/PCIE.CLK_N

To create slices for selected nets, the init.json file should be created with following content:

{
  "netclass": "",
  "nets": [
    "/DDR5 SODIMM/A.CA0",
    "/DDR5 SODIMM/A.DQ12",
    "/FPGA MGT Interface/PCIE.CLK_P",
    "/FPGA MGT Interface/PCIE.CLK_N"
  ]
}

To create the file, run:

echo '{
  "netclass": "",
  "nets": [
    "/DDR5 SODIMM/A.CA0",
    "/DDR5 SODIMM/A.DQ1",
    "/FPGA MGT Interface/PCIE.CLK_P",
    "/FPGA MGT Interface/PCIE.CLK_N"
  ]
}' > init.json

Generate configuration for the slicer¶

Create the net_configs directory and use wrapper_settings to generate a configuration file for each net:

mkdir net_configs/
si-wrapper settings -i init.json -o net_configs

Generate slices¶

for file in net_configs/*; do 
    si-wrapper slice -f $file  
done

As a result, the slices directory should be created containing subdirectories named as nets.

Simulate using gerber2ems¶

Following the installation guide, clone and install gerber2ems.

Enter the slices directory and follow the instructions from the gerber2ems README to perform simulation.

Generate bitmaps of created slices¶

Note: This step is optional.

cd slices
for dir in ./*/; do
    cd $dir
    kicad-cli pcb export gerbers --no-protel-ext -o fab/ *.kicad_pcb
    kicad-cli pcb export drill --format gerber --excellon-separate-th -o fab/ *.kicad_pcb
    si-wrapper gerber2png
    cd ../
done

Note: Optionally, kicad-make can be used to aid the process of KiCad output generation by replacing:

kicad-cli pcb export gerbers --no-protel-ext -o fab/ *.kicad_pcb
kicad-cli pcb export drill --format gerber --excellon-separate-th -o fab/ *.kicad_pcb

with

kmake gerber -xe

Slicing examples¶

Below, you can see examples of generated slices for the /DDR5 SODIMM/B.DQ12 net with different settings for neighboring. The first one has no reduced layout, the second has the neighboring net threshold set to 2 neighboring points, the third to 10 neighboring points and the fourth to 50 neighboring points. The neighboring net distance offset is set to 0.3 mm for each case.