Sample buffer Data for testing

[Tinku]

For testing my project without hardware I need a sample buffer data of which is stream of bytes buffer, so I created

const sample_bufferData = Buffer.alloc(300);

then

the data I received is in this format, for ex: 1st four bytes has ascii format address from sample_bufferData[0-3], and then 2 bytes of data format of BCD i.e., address 4-5 bytes
.
for this first 6 buffer bytes 0 to 3 and 4to 5 How can I declare them?

Many thanks

[Steve-Mcl]

You can do it in a function using the node Buffer functions like writeInt16BE etc or you can use a helper node.

e.g. node-red-contrib-buffer-parser has a companion node named buffer-maker

Here is an example based on a Balluff TCP Command (Command L, page 58 in this manual)...

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[Tinku]

Hallo @Steve-Mcl ,

Many thanks for your help. I opened a separate post because as I currently don't have hardware and trying to write function where I want to get sample buffer data by triggering this read process. But now with this buffer maker node I can be able to do sample buffer data what I can get from this Balluff unit.
Many thanks again man. You are awesome

[Tinku]

By generating Fake data I have a BCD data type of 3 bytes length, Just say for example: 8000(decimal)

In BCD I can give it as: 000000001000000000000000.
In BufferMaker node I gave type as BCD(le) and length of 3 bytes and in msg I gave 000000001000000000000000
Why the buffer is creating 6 bytes where I gave length as 3 ?

[Steve-Mcl]

Because BCD is a 16bit operation.

What numeric value are you trying to send (as in decimal or hexadecimal)?

[Tinku]

By generating fake data from rfid chip, I get BCD and ASCII format data types:
For ASCII I’m clear as: For ex: a length of 32 bytes: the unused bytes as 0 and used bytes with asciistring
By BCD kind of format data for ex I want to generate +102.8, (for + sign char B is used, - sign char D and for . E is used)--> B102E800 is the BCD value I get,
I gave in buffer maker : type of BCD length of 4 bytes and string as B102E800,

[Steve-Mcl]

@Tinku

By BCD kind of format data for ex I want to generate +102.8, (for + sign char B is used, - sign char D and for . E is used)--> B102E800 is the BCD value I get,

ok, so I'm sure you realise, BCD is Binary Coded Decimal and its hexadecimal value will never contain any letters (e.g. 16bit BCD is 0x0000 > 0x9999, 32bit BCD is 0x0000000 > 0x99999999). What you have there is a custom data type.

You will need to construct those ascii characters then use the buffer maker ASCII type.

e.g...

/*
for + sign char B is used
for - sign char D is used 
for . E is used

e.g. +102.8 == B102E800
*/

const DP = "E";
const val = msg.payload.toString().trim();
const parts = val.split(".");
let sign = "B";
let leftOfDP = parts[0];
let rightOfDP = (parts[1] || "0");
if (val.startsWith("-")) {
    sign = "D";
    leftOfDP = leftOfDP.substring(1);//drop "-"
}
if (leftOfDP.length > 3) {
    node.error(`Cannot convert ${val} to custom BCD format`, msg);
    return;
}

leftOfDP = leftOfDP.padStart(3, "0");
rightOfDP = rightOfDP.padEnd(3, "0").substring(0, 3);

msg.payload = `${sign}${leftOfDP}${DP}${rightOfDP}`

return msg;

[Tinku]

Hallo Steve-Mcl,

got some doubts with tcp nodes: is it correct what I am doing.?
I start read or write process using tcp request node and then I get response from tcp/ip device, with function node I can get ACK or NAK, with ACK I need to reply STX(start of text) and then with tcp in node as listener with port no is it correct?

[Steve-Mcl]

The best way to do this is to actually fake the device.

Example...

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