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Only getting data when 'rubbing' wires
Clash Royale CLAN TAG#URR8PPP
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1
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I'm trying to use cansniffer and candump to read rhe canbus data in my car with a raspberry pi and the PiCAN 2 board, but I have run into a weird issue I can't explain.
Situation:
I've located the CAN-H and CAN-L wires in the car.
Stripped part of the wires and used wires with an alligator clips on both ends to clamp to the stripped part.
On the PiCAN board I attached wires to the CAN-H and CAN-L ports, each wire is stripped at the end, and also connected with alligator clamps.
The problem:
I only see data from candump / cansniffer when i take off one of the clamps and 'rub' the wire against the clamp. Which seems really weird, and I have never experienced anything like this. Anyone here has some tips that I can try?
Edit:
I have tried using just wires, different wire gauge, but the problem stays.
automotive can
edited 1 hour ago
Dave Tweed♦
110k9132236
asked 4 hours ago
Avdhulst
62
New contributor
Avdhulst is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
 |Â
show 2 more comments
up vote
1
down vote
favorite
I'm trying to use cansniffer and candump to read rhe canbus data in my car with a raspberry pi and the PiCAN 2 board, but I have run into a weird issue I can't explain.
Situation:
I've located the CAN-H and CAN-L wires in the car.
Stripped part of the wires and used wires with an alligator clips on both ends to clamp to the stripped part.
On the PiCAN board I attached wires to the CAN-H and CAN-L ports, each wire is stripped at the end, and also connected with alligator clamps.
The problem:
I only see data from candump / cansniffer when i take off one of the clamps and 'rub' the wire against the clamp. Which seems really weird, and I have never experienced anything like this. Anyone here has some tips that I can try?
Edit:
I have tried using just wires, different wire gauge, but the problem stays.
automotive can
edited 1 hour ago
Dave Tweed♦
110k9132236
asked 4 hours ago
Avdhulst
62
New contributor
Avdhulst is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
What is candump and cansniffer?
– Andy aka
4 hours ago
Capitals matter.
– Transistor
4 hours ago
Rubbing the wires is producing a noise signal - contact bounce.
– Chu
4 hours ago
Perhaps the wires are corroded and that is causing a poor or no connection. The rubbing is breaking through the corrosion...
– Solar Mike
3 hours ago
CAN bus is a differential signal. Disconnecting one side (+ or -) creates a pathological condition. You are no doubt "hearing" noise at that point.
– mike65535
2 hours ago
 |Â
show 2 more comments
up vote
1
down vote
favorite
up vote
1
down vote
favorite
I'm trying to use cansniffer and candump to read rhe canbus data in my car with a raspberry pi and the PiCAN 2 board, but I have run into a weird issue I can't explain.
Situation:
I've located the CAN-H and CAN-L wires in the car.
Stripped part of the wires and used wires with an alligator clips on both ends to clamp to the stripped part.
On the PiCAN board I attached wires to the CAN-H and CAN-L ports, each wire is stripped at the end, and also connected with alligator clamps.
The problem:
I only see data from candump / cansniffer when i take off one of the clamps and 'rub' the wire against the clamp. Which seems really weird, and I have never experienced anything like this. Anyone here has some tips that I can try?
Edit:
I have tried using just wires, different wire gauge, but the problem stays.
automotive can
edited 1 hour ago
Dave Tweed♦
110k9132236
asked 4 hours ago
Avdhulst
62
New contributor
Avdhulst is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
I'm trying to use cansniffer and candump to read rhe canbus data in my car with a raspberry pi and the PiCAN 2 board, but I have run into a weird issue I can't explain.
Situation:
I've located the CAN-H and CAN-L wires in the car.
Stripped part of the wires and used wires with an alligator clips on both ends to clamp to the stripped part.
On the PiCAN board I attached wires to the CAN-H and CAN-L ports, each wire is stripped at the end, and also connected with alligator clamps.
The problem:
I only see data from candump / cansniffer when i take off one of the clamps and 'rub' the wire against the clamp. Which seems really weird, and I have never experienced anything like this. Anyone here has some tips that I can try?
Edit:
I have tried using just wires, different wire gauge, but the problem stays.
automotive can
automotive can
edited 1 hour ago
Dave Tweed♦
110k9132236
asked 4 hours ago
Avdhulst
62
New contributor
Avdhulst is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 1 hour ago
Dave Tweed♦
110k9132236
asked 4 hours ago
Avdhulst
62
New contributor
Avdhulst is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 1 hour ago
Dave Tweed♦
110k9132236
edited 1 hour ago
Dave Tweed♦
110k9132236
edited 1 hour ago
Dave Tweed♦
110k9132236
110k9132236
asked 4 hours ago
Avdhulst
62
New contributor
Avdhulst is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 4 hours ago
Avdhulst
62
asked 4 hours ago
Avdhulst
62
62
New contributor
Avdhulst is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Avdhulst is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Avdhulst is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
What is candump and cansniffer?
– Andy aka
4 hours ago
Capitals matter.
– Transistor
4 hours ago
Rubbing the wires is producing a noise signal - contact bounce.
– Chu
4 hours ago
Perhaps the wires are corroded and that is causing a poor or no connection. The rubbing is breaking through the corrosion...
– Solar Mike
3 hours ago
CAN bus is a differential signal. Disconnecting one side (+ or -) creates a pathological condition. You are no doubt "hearing" noise at that point.
– mike65535
2 hours ago
 |Â
show 2 more comments
What is candump and cansniffer?
– Andy aka
4 hours ago
Capitals matter.
– Transistor
4 hours ago
Rubbing the wires is producing a noise signal - contact bounce.
– Chu
4 hours ago
Perhaps the wires are corroded and that is causing a poor or no connection. The rubbing is breaking through the corrosion...
– Solar Mike
3 hours ago
CAN bus is a differential signal. Disconnecting one side (+ or -) creates a pathological condition. You are no doubt "hearing" noise at that point.
– mike65535
2 hours ago
What is candump and cansniffer?
– Andy aka
4 hours ago
What is candump and cansniffer?
– Andy aka
4 hours ago
Capitals matter.
– Transistor
4 hours ago
Capitals matter.
– Transistor
4 hours ago
Rubbing the wires is producing a noise signal - contact bounce.
– Chu
4 hours ago
Rubbing the wires is producing a noise signal - contact bounce.
– Chu
4 hours ago
Perhaps the wires are corroded and that is causing a poor or no connection. The rubbing is breaking through the corrosion...
– Solar Mike
3 hours ago
Perhaps the wires are corroded and that is causing a poor or no connection. The rubbing is breaking through the corrosion...
– Solar Mike
3 hours ago
CAN bus is a differential signal. Disconnecting one side (+ or -) creates a pathological condition. You are no doubt "hearing" noise at that point.
– mike65535
2 hours ago
CAN bus is a differential signal. Disconnecting one side (+ or -) creates a pathological condition. You are no doubt "hearing" noise at that point.
– mike65535
2 hours ago
 |Â
show 2 more comments
3 Answers
3
active
oldest
votes
up vote
2
down vote
You need to connect three wires: CANH, CANL, and ground. The CAN lines are differential, but are still ground-referenced. That's another way of saying that your CAN receiver probably has a limited common mode input range.
If you do have ground connected, then you are not making good connections the the CAN lines. Make sure the clips are digging into the bare wires properly. Make sure that the teeth of the clips are on the wires, then manually squeeze the clips together more.
Also make sure you don't have the CAN lines flipped. The best way to identify the lines is to look at their voltages on a scope. When the bus is idle, both lines will be at the same voltage, usually around 2.5 V. When the bus is in the dominant state, then CANH should be about 1.8 V higher than CANL.
Keep the total wire length from the car wires to your receiver short. CAN is not meant to be in a star configuration, which is what you are creating. CAN will still work if the stubs are short enough. The CAN bus will already have a terminator at each end, so make sure your receiver does not have any terminator enabled. Some receivers have the option for this. Remember that in CAN, it is the bus that is terminated, not individual devices.
answered 18 mins ago
Olin Lathrop
278k28331782
add a comment |Â
up vote
0
down vote
The cables might be aluminum. It is used in cars and power lines as they are very good conductor, lighter and cheaper than copper.
The problem with aluminum is that it's very difficult to make connections because of the oxide layer that forms rapidly exposed to the oxygen of the air.
If indeed they are aluminum, you can try to crimp the cable, or putting some oil on the wire and try to scratch through it while connecting the cables.
answered 2 hours ago
Damien
46516
add a comment |Â
up vote
0
down vote
Diff. logic Voltage readings must have good conductance ( or contact) and low inductive (short gnd wire) and shield of paired signals to 0V. Otherwise, poor signal integrity will occur.
I suggest you use STP wire or separately twisted pair sig+gnd. AWG24 to 30 magnet wire or thin insulated wire. This may reduce signal wire impedance to prevent ringing on short cables.
Examine the wire contact resistance for insulation issues but also note that your fingers absorb stray coupling to gnd. by lowering the common mode impedance while rubbing which is improved by twisted pairs to gnd for each signal. It also adds capacitance to the differential impedance too, so CANBUS interfacing requires knowledge of impedance matching and stray ground noise caused by your SMPS which is then improved by bonding of receiver 0Vdc to chassis. (like an earth gnd.)
answered 1 hour ago
Tony EE rocketscientist
59k22088
add a comment |Â
3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
2
down vote
You need to connect three wires: CANH, CANL, and ground. The CAN lines are differential, but are still ground-referenced. That's another way of saying that your CAN receiver probably has a limited common mode input range.
If you do have ground connected, then you are not making good connections the the CAN lines. Make sure the clips are digging into the bare wires properly. Make sure that the teeth of the clips are on the wires, then manually squeeze the clips together more.
Also make sure you don't have the CAN lines flipped. The best way to identify the lines is to look at their voltages on a scope. When the bus is idle, both lines will be at the same voltage, usually around 2.5 V. When the bus is in the dominant state, then CANH should be about 1.8 V higher than CANL.
Keep the total wire length from the car wires to your receiver short. CAN is not meant to be in a star configuration, which is what you are creating. CAN will still work if the stubs are short enough. The CAN bus will already have a terminator at each end, so make sure your receiver does not have any terminator enabled. Some receivers have the option for this. Remember that in CAN, it is the bus that is terminated, not individual devices.
answered 18 mins ago
Olin Lathrop
278k28331782
add a comment |Â
up vote
2
down vote
You need to connect three wires: CANH, CANL, and ground. The CAN lines are differential, but are still ground-referenced. That's another way of saying that your CAN receiver probably has a limited common mode input range.
If you do have ground connected, then you are not making good connections the the CAN lines. Make sure the clips are digging into the bare wires properly. Make sure that the teeth of the clips are on the wires, then manually squeeze the clips together more.
Also make sure you don't have the CAN lines flipped. The best way to identify the lines is to look at their voltages on a scope. When the bus is idle, both lines will be at the same voltage, usually around 2.5 V. When the bus is in the dominant state, then CANH should be about 1.8 V higher than CANL.
Keep the total wire length from the car wires to your receiver short. CAN is not meant to be in a star configuration, which is what you are creating. CAN will still work if the stubs are short enough. The CAN bus will already have a terminator at each end, so make sure your receiver does not have any terminator enabled. Some receivers have the option for this. Remember that in CAN, it is the bus that is terminated, not individual devices.
answered 18 mins ago
Olin Lathrop
278k28331782
add a comment |Â
up vote
2
down vote
up vote
2
down vote
You need to connect three wires: CANH, CANL, and ground. The CAN lines are differential, but are still ground-referenced. That's another way of saying that your CAN receiver probably has a limited common mode input range.
If you do have ground connected, then you are not making good connections the the CAN lines. Make sure the clips are digging into the bare wires properly. Make sure that the teeth of the clips are on the wires, then manually squeeze the clips together more.
Also make sure you don't have the CAN lines flipped. The best way to identify the lines is to look at their voltages on a scope. When the bus is idle, both lines will be at the same voltage, usually around 2.5 V. When the bus is in the dominant state, then CANH should be about 1.8 V higher than CANL.
Keep the total wire length from the car wires to your receiver short. CAN is not meant to be in a star configuration, which is what you are creating. CAN will still work if the stubs are short enough. The CAN bus will already have a terminator at each end, so make sure your receiver does not have any terminator enabled. Some receivers have the option for this. Remember that in CAN, it is the bus that is terminated, not individual devices.
answered 18 mins ago
Olin Lathrop
278k28331782
You need to connect three wires: CANH, CANL, and ground. The CAN lines are differential, but are still ground-referenced. That's another way of saying that your CAN receiver probably has a limited common mode input range.
If you do have ground connected, then you are not making good connections the the CAN lines. Make sure the clips are digging into the bare wires properly. Make sure that the teeth of the clips are on the wires, then manually squeeze the clips together more.
Also make sure you don't have the CAN lines flipped. The best way to identify the lines is to look at their voltages on a scope. When the bus is idle, both lines will be at the same voltage, usually around 2.5 V. When the bus is in the dominant state, then CANH should be about 1.8 V higher than CANL.
Keep the total wire length from the car wires to your receiver short. CAN is not meant to be in a star configuration, which is what you are creating. CAN will still work if the stubs are short enough. The CAN bus will already have a terminator at each end, so make sure your receiver does not have any terminator enabled. Some receivers have the option for this. Remember that in CAN, it is the bus that is terminated, not individual devices.
answered 18 mins ago
Olin Lathrop
278k28331782
answered 18 mins ago
Olin Lathrop
278k28331782
answered 18 mins ago
Olin Lathrop
278k28331782
answered 18 mins ago
Olin Lathrop
278k28331782
278k28331782
add a comment |Â
add a comment |Â
up vote
0
down vote
The cables might be aluminum. It is used in cars and power lines as they are very good conductor, lighter and cheaper than copper.
The problem with aluminum is that it's very difficult to make connections because of the oxide layer that forms rapidly exposed to the oxygen of the air.
If indeed they are aluminum, you can try to crimp the cable, or putting some oil on the wire and try to scratch through it while connecting the cables.
answered 2 hours ago
Damien
46516
add a comment |Â
up vote
0
down vote
The cables might be aluminum. It is used in cars and power lines as they are very good conductor, lighter and cheaper than copper.
The problem with aluminum is that it's very difficult to make connections because of the oxide layer that forms rapidly exposed to the oxygen of the air.
If indeed they are aluminum, you can try to crimp the cable, or putting some oil on the wire and try to scratch through it while connecting the cables.
answered 2 hours ago
Damien
46516
add a comment |Â
up vote
0
down vote
up vote
0
down vote
The cables might be aluminum. It is used in cars and power lines as they are very good conductor, lighter and cheaper than copper.
The problem with aluminum is that it's very difficult to make connections because of the oxide layer that forms rapidly exposed to the oxygen of the air.
If indeed they are aluminum, you can try to crimp the cable, or putting some oil on the wire and try to scratch through it while connecting the cables.
answered 2 hours ago
Damien
46516
The cables might be aluminum. It is used in cars and power lines as they are very good conductor, lighter and cheaper than copper.
The problem with aluminum is that it's very difficult to make connections because of the oxide layer that forms rapidly exposed to the oxygen of the air.
If indeed they are aluminum, you can try to crimp the cable, or putting some oil on the wire and try to scratch through it while connecting the cables.
answered 2 hours ago
Damien
46516
answered 2 hours ago
Damien
46516
answered 2 hours ago
Damien
46516
answered 2 hours ago
Damien
46516
46516
add a comment |Â
add a comment |Â
up vote
0
down vote
Diff. logic Voltage readings must have good conductance ( or contact) and low inductive (short gnd wire) and shield of paired signals to 0V. Otherwise, poor signal integrity will occur.
I suggest you use STP wire or separately twisted pair sig+gnd. AWG24 to 30 magnet wire or thin insulated wire. This may reduce signal wire impedance to prevent ringing on short cables.
Examine the wire contact resistance for insulation issues but also note that your fingers absorb stray coupling to gnd. by lowering the common mode impedance while rubbing which is improved by twisted pairs to gnd for each signal. It also adds capacitance to the differential impedance too, so CANBUS interfacing requires knowledge of impedance matching and stray ground noise caused by your SMPS which is then improved by bonding of receiver 0Vdc to chassis. (like an earth gnd.)
answered 1 hour ago
Tony EE rocketscientist
59k22088
add a comment |Â
up vote
0
down vote
Diff. logic Voltage readings must have good conductance ( or contact) and low inductive (short gnd wire) and shield of paired signals to 0V. Otherwise, poor signal integrity will occur.
I suggest you use STP wire or separately twisted pair sig+gnd. AWG24 to 30 magnet wire or thin insulated wire. This may reduce signal wire impedance to prevent ringing on short cables.
Examine the wire contact resistance for insulation issues but also note that your fingers absorb stray coupling to gnd. by lowering the common mode impedance while rubbing which is improved by twisted pairs to gnd for each signal. It also adds capacitance to the differential impedance too, so CANBUS interfacing requires knowledge of impedance matching and stray ground noise caused by your SMPS which is then improved by bonding of receiver 0Vdc to chassis. (like an earth gnd.)
answered 1 hour ago
Tony EE rocketscientist
59k22088
add a comment |Â
up vote
0
down vote
up vote
0
down vote
Diff. logic Voltage readings must have good conductance ( or contact) and low inductive (short gnd wire) and shield of paired signals to 0V. Otherwise, poor signal integrity will occur.
I suggest you use STP wire or separately twisted pair sig+gnd. AWG24 to 30 magnet wire or thin insulated wire. This may reduce signal wire impedance to prevent ringing on short cables.
Examine the wire contact resistance for insulation issues but also note that your fingers absorb stray coupling to gnd. by lowering the common mode impedance while rubbing which is improved by twisted pairs to gnd for each signal. It also adds capacitance to the differential impedance too, so CANBUS interfacing requires knowledge of impedance matching and stray ground noise caused by your SMPS which is then improved by bonding of receiver 0Vdc to chassis. (like an earth gnd.)
answered 1 hour ago
Tony EE rocketscientist
59k22088
Diff. logic Voltage readings must have good conductance ( or contact) and low inductive (short gnd wire) and shield of paired signals to 0V. Otherwise, poor signal integrity will occur.
I suggest you use STP wire or separately twisted pair sig+gnd. AWG24 to 30 magnet wire or thin insulated wire. This may reduce signal wire impedance to prevent ringing on short cables.
Examine the wire contact resistance for insulation issues but also note that your fingers absorb stray coupling to gnd. by lowering the common mode impedance while rubbing which is improved by twisted pairs to gnd for each signal. It also adds capacitance to the differential impedance too, so CANBUS interfacing requires knowledge of impedance matching and stray ground noise caused by your SMPS which is then improved by bonding of receiver 0Vdc to chassis. (like an earth gnd.)
answered 1 hour ago
Tony EE rocketscientist
59k22088
edited 1 hour ago
answered 1 hour ago
Tony EE rocketscientist
59k22088
answered 1 hour ago
Tony EE rocketscientist
59k22088
answered 1 hour ago
Tony EE rocketscientist
59k22088
59k22088
add a comment |Â
add a comment |Â
Avdhulst is a new contributor. Be nice, and check out our Code of Conduct.
Avdhulst is a new contributor. Be nice, and check out our Code of Conduct.
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What is candump and cansniffer?
– Andy aka
4 hours ago
Capitals matter.
– Transistor
4 hours ago
Rubbing the wires is producing a noise signal - contact bounce.
– Chu
4 hours ago
Perhaps the wires are corroded and that is causing a poor or no connection. The rubbing is breaking through the corrosion...
– Solar Mike
3 hours ago
CAN bus is a differential signal. Disconnecting one side (+ or -) creates a pathological condition. You are no doubt "hearing" noise at that point.
– mike65535
2 hours ago