JSON-for-VHDL is a library to parse and query JSON data structures in VHDL. The complete functionality is hosted in a single VHDL package, without special dependencies.
The JSON-for-VHDL library can be used to parse and query JSON data structures, which are read from disk. The data structure is read via VHDL file I/O functions and procedures and parsed into a internal compressed representation. While the parsing is done, a lightwight index is created to ease the navigation on the data structure.
Values can be selected by simple path expressions.
JavaScript Object Notation (JSON) Data Interchange Format is specified in RFC 7159.
Here is a short example *.json file, which describes two common FPGA boards.
{ "ML505": {
"FPGA": "XC5VLX50T-1FF1136",
"Eth": [{
"PHY-Int": "GMII",
"Device": "MARVEL_88E1111",
"Address": "0x74"
}]
},
"KC705": {
"FPGA": "XC7K325T-2FFG900C",
"Eth": [{
"PHY-Int": "GMII",
"Device": "MARVEL_88E1111",
"Address": "0x74"
}],
"IIC": [{
"Type": "Switch",
"Adr": "0x85",
"Devices": [{
"Name": "Si570",
"Address": "0x3A"
}]
}]
}
}
Reference the JSON package in VHDL:
use work.json.all;
Load a external *.json file, parse the data structure and select a value:
architecture rtl of Test is
constant ConfigFile : STRING := "Boards.json";
constant JSONContent : T_JSON := jsonLoad(ConfigFile);
begin
assert (JSONContent.Error(1) = C_JSON_NUL)
report "Error: " & JSONContent.Error
severity ERROR;
assert FALSE
report "Query='KC705/Eth/0/Address' Value='" & jsonGetString(JSONContent, "KC705/Eth/0/Address") & "'"
severity NOTE;
-- print the compressed file content
-- assert FALSE
-- report "JSON: " & JSONContent.Content severity NOTE;
end architecture;
The library can be downloaded as a zip-file (latest 'master' branch) or
cloned with git from GitHub. GitHub offers HTTPS and SSH as transfer protocols.
For SSH protocol use the URL ssh:https://[email protected]:Paebbels/JSON-for-VHDL.git or command
line instruction:
cd <GitRoot>
git clone ssh:https://[email protected]:Paebbels/JSON-for-VHDL.git JSON
For HTTPS protocol use the URL https://github.com/Paebbels/JSON-for-VHDL.git or command
line instruction:
cd <GitRoot>
git clone https://github.com/Paebbels/JSON-for-VHDL.git JSON