CAN Message Timing

[MichaelBMiner]

Hello,

In my DBC file I am seeing timing data.

BA_ "BusType" "CAN";
BA_ "ProtocolType" "CANopen";
BA_ "GenMsgCycleTime" BO_ 662 1000;
BA_ "GenMsgDelayTime" BO_ 662 5000;
BA_ "GenMsgSendType" BO_ 662 0;
BA_ "GenMsgCycleTime" BO_ 406 250;
BA_ "GenMsgDelayTime" BO_ 406 1250;
BA_ "GenMsgSendType" BO_ 406 0;

Is there a way to extract this from this signal?

[MichaelBMiner]

@xR3b0rn Do you or any of the other devs have insight?

[xR3b0rn]

@MichaelBMiner these are the attribute values. You can get them by iterating over the AttributeValues of a Signal e.g.:

auto printer = [](const auto& value) { std::cout << value; };
const auto& sig = ... // get sig from somewhere
for (const auto& attr : sig.AttributeValues())
{
    std::cout << attr.Name() << ": ";
    std::visit(printer, attr.Value());
    std::cout << "\n";
}

Edit: Of course IMessage also provides a AttributeValues-function.

[MichaelBMiner]

@xR3b0rn I am using C for this. My code is as follows.

for (uint32_t i = 0; i < num_dbc_can_ids; i++) {
			const dbcppp_Message* msg = dbcppp_NetworkMessages_Get(net, i);
			uint16_t num_spns = dbcppp_MessageSignals_Size(msg);
			if (dbcppp_MessageId(msg) == frame.can_id) {
				data->can_id = frame.can_id;
				data->num_spns = num_spns;
				for (uint64_t j = 0; j < num_spns; j++) {
					const dbcppp_Signal* sig = dbcppp_MessageSignals_Get(msg, j);
					(void)memcpy(data->spns[j].name, dbcppp_SignalName(sig), MAX_NAME_LENGTH);
					(void)memcpy(data->spns[j].units, dbcppp_SignalUnit(sig), UNITS_LEN);
					uint64_t raw = dbcppp_SignalDecode(sig, frame.data);
					double phys = dbcppp_SignalRawToPhys(sig, raw);

					uint8_t x;
					uint64_t att_size = dbcppp_SignalAttributeValues_Size(sig);
					for(x=0; x<att_size; i++) {
						const dbcppp_Attribute* attr = dbcppp_SignalAttributeValues_Get(sig, i);
						printf("Name %s Value %d", dbcppp_AttributeName(attr), dbcppp_AttributeValueAsInt(attr));
					}

					data->spns[j].raw = raw;
					data->spns[j].phys = phys;
					clock_gettime(CLOCK_SOURCE, &data->timestamp);
				}
			}
		}

The code works great to parse the signals. What is your code looking for when it updates the attributes?

My DBC contains data for CAN ID 1960 as follows

BO_ 1960 TO_EVSE_SE_I: 8 Vector__XXX
 SG_ EVSEPSMinimumCurrentLimitValue : 48|16@1- (0.1,0) [-3276.8|3276.7] "A" Vector__XXX
 SG_ EVSEPSMaximumCurrentLimitValue : 32|16@1- (0.1,0) [-3276.8|3276.7] "A" Vector__XXX
 SG_ EVSEPSMinimumVoltageLimitValue : 16|16@1- (0.1,0) [-3276.8|3276.7] "V" Vector__XXX
 SG_ EVSEPSMaximumVoltageLimitValue : 0|16@1- (0.1,0) [-3276.8|3276.7] "V" Vector__XXX

Attributes are defined at the end of the file as so.

CM_ SG_ 1960 EVSEPSMinimumCurrentLimitValue "Power stack minimum current limit";
CM_ SG_ 1960 EVSEPSMaximumCurrentLimitValue "Power stack maximum current limit";
CM_ SG_ 1960 EVSEPSMinimumVoltageLimitValue "Power stack minumum voltage limit";
CM_ SG_ 1960 EVSEPSMaximumVoltageLimitValue "Power stack maximum voltage limit";
BA_ "GenMsgSendType" BO_ 1960 0;
BA_ "GenMsgDelayTime" BO_ 1960 2500;
BA_ "GenMsgCycleTime" BO_ 1960 500;

When I run the inner loop to get the attributes, I am told there are none.

[MichaelBMiner]

Digging around I was able to find the network attributes. Then I attempted to get the message attributes. The message attributes are empty. The network attributes find 9 entries.

BA_DEF_DEF_  "BusType" "";
BA_DEF_DEF_  "GenSigStartValue" 0;
BA_DEF_DEF_  "CO_MsgCategory" 0;
BA_DEF_DEF_  "GenMsgCycleTime" 0;
BA_DEF_DEF_  "GenMsgDelayTime" 100;
BA_DEF_DEF_  "GenMsgSendType" "";
BA_DEF_DEF_  "ProtocolType" "CANopen";
BA_DEF_DEF_  "CANopenApplProfile" 301;
BA_DEF_DEF_  "CO_MsgColourSupported" 1;

If I continue I end up finding some.
It looks like I found it. Using the following it seems to work.

uint32_t num_msg_attr = dbcppp_MessageAttributeValues_Size(msg);
			printf("Num msg attrs %d\n", num_msg_attr);
			for(uint16_t t=0; t<num_msg_attr; t++) {
				const dbcppp_Attribute* attr = dbcppp_MessageAttributeValues_Get(msg, t);
				printf("Name %s\n", dbcppp_AttributeName(attr));
			}

I am just wondering if there is some documentation or a Doxygen report I could reference.

[MichaelBMiner]

Last comment I will make is that I am getting the error

terminate called after throwing an instance of 'std::bad_variant_access'
  what():  std::get: wrong index for variant

uint32_t num_msg_attr = dbcppp_MessageAttributeValues_Size(msg);
			printf("Num msg attrs %d\n", num_msg_attr);
			for(uint16_t t=0; t<num_msg_attr; t++) {
				const dbcppp_Attribute* attr = dbcppp_MessageAttributeValues_Get(msg, t);
				printf("Name %s Value as String %s\n", dbcppp_AttributeName(attr), dbcppp_AttributeValueAsString(attr));
			}

This only started after I added the dbcppp_AttributeValueAsString function call.

[xR3b0rn]

what(): std::get: wrong index for variant indicates you expect a wrong attribute value type. Are you sure the type is string?

You can query the type using dbcppp_AttributeValueType(attr):

uint32_t num_msg_attr = dbcppp_MessageAttributeValues_Size(msg);
printf("Num msg attrs %d\n", num_msg_attr);
for(uint16_t t=0; t<num_msg_attr; t++) {
    const dbcppp_Attribute* attr = dbcppp_MessageAttributeValues_Get(msg, t);
    switch (dbcppp_AttributeValueType(attr))
    {
    case dbcppp_AttributeValueType_Int:
        printf("Name %s Value as Int %d\n", dbcppp_AttributeName(attr), dbcppp_AttributeValueAsInt(attr));
        break;
    case dbcppp_AttributeValueType_Double:
        printf("Name %s Value as Double %f\n", dbcppp_AttributeName(attr), dbcppp_AttributeValueAsDouble(attr));
        break;
    case dbcppp_AttributeValueType_String:
        printf("Name %s Value as String %s\n", dbcppp_AttributeName(attr), dbcppp_AttributeValueAsString(attr));
        break;
    }
}

[MichaelBMiner]

They are doubles! I was assuming integers! Thank you. This code base is amazing.