XS07 Script Production Example: I2C protocol decoder

The next example is a simple I2C protocol decoder. The example shows, how to analyse logic signals and how to generate a struct signal.

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// input: an array of all input signals
// in0: primary input of type ISamplePointer,IReadableSamples
// in1..: additional inputs of type ISamplePointer,IReadableSamples
// out: output signal of type ???
// console: console output of type MessageConsoleStream
// iter: iterator of type ISamplesIterator
// progress: progess control of type  IScriptProgress
 
// input
var sda <:ISamplePointer:> = input[0]; // sda input
var scl <:ISamplePointer:> = input[1]; // scl input
 
// state
var states, state, started, pos, bits, address, byt, bytes, write, members, extAddressing;
 
// init
if (state == null) {
 
    // signal
    members = out.createMembers(6);
    out.createMember(members, 0, "RW",
        ISample.STRUCT_TYPE_ENUM, null, -1);
    out.createMember(members, 1, "Address",
        ISample.STRUCT_TYPE_INTEGER, null, ISample.FORMAT_HEXADECIMAL);
    out.createMember(members, 2, "Data",
        ISample.STRUCT_TYPE_BINARY, null, ISample.FORMAT_HEXADECIMAL);
    out.createMember(members, 3, "Bytes",
        ISample.STRUCT_TYPE_INTEGER, null, -1);
    out.createMember(members, 4, "Duration",
        ISample.STRUCT_TYPE_INTEGER, null, -1);
    out.createMember(members, 5, "Addressing",
        ISample.STRUCT_TYPE_ENUM, null, -1);
 
    // states
    states = {
        INIT: 0,
        STARTED: 1,
        GOT_ADDRESS: 2,
        READ_DATA: 3
    };
    state = states.INIT;
}
 
// iterate
progress.cont();
while (iter.hasNext()) {
    var current <:Long:> = iter.next(out);
 
    // start condition
    if (sda.isEdge(-1) && scl.isHigh()) {
        state = states.STARTED;
        started = current;
        bytes = 0;
        extAddressing = null;
        bits = 0;
        continue;
    }
 
    // stop condition
    if (state != states.INIT && sda.isEdge(1) && scl.isHigh()) {
        state = 0;
        members[0].setValue(read == 1 ? "Read" : "Write");
        members[1].setValue(new java.lang.Integer(address));
        members[2].setValue(new java.math.BigInteger(data, 16)
            .toByteArray());
        members[3].setValue(new java.lang.Integer(bytes));
        members[4].setValue(new java.lang.Long(current - started));
        members[5].setValue(extAddressing ? "10 Bit" : "7 Bit");
        out.write(started, false, members);
        continue;
    }
 
    // address
    if (state == states.STARTED && scl.isEdge(1)) {
        if (bits == 0) {
            address = 0;
            data = "";
            pos = current;
        }
        bits++;
        address = (address << 1) | (sda.isHigh() ? 1 : 0);
        if (bits == 7) {
            state = states.GOT_ADDRESS;
            bits = 0;
        }
        continue;
    }
 
    // rw / ackn
    if (state == states.GOT_ADDRESS && scl.isEdge(1)) {
        bits++;
        if (bits == 1) { // rw
            read = sda.isHigh();
        }
        if (bits == 2) { // ackn
            var ackn = sda.isHigh();
            state = states.READ_DATA;
            bits = 0;
        }
        continue;
    }
 
    // data
    if (state == states.READ_DATA && scl.isEdge(1)) {
        if (bits == 0) {
            byt = 0;
            pos = current;
        }
        bits++;
        byt = (byt << 1) | (sda.isHigh() ? 1 : 0);
        if (bits == 8) {
            if (extAddressing == null) {
                if ((address & 0x7c) == 0x78) {
                    address = (address & 3) << 8 | byt;
                    extAddressing = 1;
                } else {
                    extAddressing = 0;
                    bytes++;
                    data += byt.toString(16);
                }
            } else {
                bytes++;
                data += byt.toString(16);
            }
        }
        if (bits == 9) { // ackn
            var ackn = sda.isHigh();
            bits = 0;
        }
        continue;
    }
}

About Signal Scripts Open JavaDoc Reference

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Result

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