239 lines
10 KiB
Markdown
239 lines
10 KiB
Markdown
# FT86 cars (Subaru BRZ, Toyota 86, Scion FR-S)
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Here is information on some of the PIDs that you're most likely to use with
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RaceChrono and equations to get the right scale, etc.
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## Recommended PIDs:
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Here are PIDs and RaceChrono equations for data channels that should be enough
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for most people:
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Channel name | PID | Equation | Notes
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------------ | --- | -------- | -----
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Accelerator position (%) | 320 | `A/2.55` |
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Brake position (%) | 209 | `min(C / 0.7, 100)` | The 0.7 divider seems to be a good value to get 100% at pressure slightly higher than those you're likely to use on the track for cars with no aero. You can use 0.8 or 0.9 if you see 100% too often.
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Steering angle | 208 | `bytesToIntLe(raw, 0, 2) * 0.1` | Positive value = turning right. You can add a `-` if you prefer it the other way around.
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Speed | 209 | `bytesToIntLe(raw, 0, 2) * 0.015694` | May want to check the multiplier against an external GPS aevice
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Engine RPM | 320 | `bitsToUIntLe(raw, 16, 14)` |
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Coolant temperature | 864 | `D - 40` |
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Engine oil temperature | 864 | `C - 40` |
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Below is a table with a few more data channels that might be useful for more
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detailed analysis. When adding more channels, be aware that it might negatively
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affect the update rate of the more essential channels, due to limited Bluetooth
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bandwidth. However, the communication protocol in RaceChrono is smart enough to
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optimize Bluetooth usage if multiple channels share the same PID. As a general
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rule, if a new channel has the same PID as an existing channel (such as
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"Throttle position" using the same PID 320 as "Accelerator position"), then
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adding it should not affect the update rates. Adding a channel based on
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a new PID (such as "Wheel speed FL") will likely affect the update rates of all
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other channels.
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Channel name | PID | Equation | Notes
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------------ | --- | -------- | -----
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Brake pressure | 209 | `C * 100` | Not sure about the units / multiplier yet.
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Clutch position | 320 | `B & 0x80 / 1.28` | Only 0% and "not 0%", unfortunately.
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Gear | 321 | `(G & 0xf) * (1 - (min(G & 0xf, 7)) / 7)` | Car calculates it based on speed, RPM and clutch position. It's pretty slow. I really doubt it's worth wasting one PID for this channel. It's not that hard to see which gear you're in based on speed and RPM in data.
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Throttle position | 320 | `G / 2.55` | This is the throttle *valve*, not pedal.
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Lateral acceleration | 208 | `bytesToIntLe(raw, 6, 1) * 0.2` | Data is noisy.
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Longitudinal acceleration | 208 | `bytesToIntLe(raw, 7, 1) * -0.1` | Data is noisy.
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Combined acceleration | 208 | `sqrt(pow2(bytesToIntLe(raw, 6, 1) * 0.2) + pow2(bytesToIntLe(raw, 7, 1) * 0.1))` |
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Z rate of rotation | 208 | `bytesToIntLe(raw, 2, 2) * -0.286478897` | Or is this "Yaw rate"?
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Wheel speed FL | 212 | `bytesToIntLe(raw, 0, 2) * 0.015694` | Use same multiplier as for "Speed".
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Wheel speed FR | 212 | `bytesToIntLe(raw, 2, 2) * 0.015694` | Use same multiplier as for "Speed".
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Wheel speed RL | 212 | `bytesToIntLe(raw, 4, 2) * 0.015694` | Use same multiplier as for "Speed".
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Wheel speed RR | 212 | `bytesToIntLe(raw, 6, 2) * 0.015694` | Use same multiplier as for "Speed".
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## Connections
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Besides the CAN pins in the OBD-II port, there is a CAN bus male port hidden
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behind the car multimedia head unit:
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It's very close to the glovebox, which makes it great for putting your CAN
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reader in the glovebox. Such a placement makes sure it's out of the way and you
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won't accidentally hit it with your leg while on the track, and also allows
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quick access for troubleshooting and experimenting. There's also a second 12V
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port inside the glovebox, which makes it easy to use a 12V-to-USB adapter
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instead of adding a 12V-to-5V converter to your hardware design.
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You can use the two middle pins of a
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[Toyota radio harness](https://www.amazon.com/gp/product/B0002BEQJ8)
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to connect to the CAN bus in a reliable way.
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It's recommended to use a ~60–90 cm (2–3') twisted pair cable between that port
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and your CAN reader. I would strongly discourage you from using the screw
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terminals on the MCP2515 board, as if the cable comes loose it can cause a short
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circuit in the CAN bus (ask me how I know), which will throw a MIL at best, and
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who knows what at worst if it happens on the track. Instead, I attached a female
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JST SM connector to the cable.
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## Stuff for nerds like me
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### PID 0x18 (24)
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Update frequency: 100 times per second.
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`0x18` is a strange PID. Judging by the low PID number (which in CAN networks
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implies higher priority) and the high update frequency, one would expect it to
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have some important data, like data for ABS or ESC systems. But based on what is
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currently known, it only has one the steering angle as a useful data channel.
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The steering angle graphs are usually relatively smooth, and this data is also
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available over `0xD0`, along with some much more important data, such as
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accelerometers.
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Channel name | Equation | Notes
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------------ | -------- | -----
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Steering angle | `bytesToIntLe(raw, 0, 2) * -0.1` | Also available in `0xD0`
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??? | `C` or `bytesToIntLe(raw, 2, 1)` | The value is 112 most of the time for me
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??? | `D` or `bytesToIntLe(raw, 3, 1)` | 0–14 sawtooth
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??? | `E` or `bytesToIntLe(raw, 4, 1)` | The value is 0 most of the time for me
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??? | `F` or `bytesToIntLe(raw, 5, 1)` | The value is 0 most of the time for me
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??? | `G` or `bytesToIntLe(raw, 6, 1)` | The value is 0 most of the time for me
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??? | `H` or `bytesToIntLe(raw, 7, 1)` | Strange data channel. It changes in a strange way when the car turns. It also has a 0-14 sawtooth over some otherwise smooth curve.
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### PID 0xD0 (208)
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Update frequency: 50 times per second.
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Channel name | Equation | Notes
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------------ | -------- | -----
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Steering angle | `bytesToIntLe(raw, 0, 2) * 0.1` | Also available in 0x18
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Z rate of rotation | `bytesToIntLe(raw, 2, 2) * -0.286478897` | The multiplier for º/sec appears to be ((90 / pi) * 100). Or is this "yaw rate"?..
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??? | `E` | Some flags?
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??? | `F` | Some flags?
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Lateral acceleration | `bytesToIntLe(raw, 6, 1) * 0.2` | Not 100% sure about the multiplier, but looks about right
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Longitudinal acceleration | `bytesToIntLe(raw, 7, 1) * -0.1` | Not 100% sure about the multiplier, but looks about right
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Combined acceleration | `sqrt(pow2(bytesToIntLe(raw, 6, 1) * 0.2) + pow2(bytesToIntLe(raw, 7, 1) * 0.1))` |
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### PID 0xD1 (209)
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Update frequency: 50 times per second.
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Length: 4 bytes
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Channel name | Equation | Notes
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------------ | -------- | -----
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Speed | `bytesToIntLe(raw, 0, 2) * 0.015694` | May want to check the multiplier against an external GPS device
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Brake position | `min(C / 0.7, 100)` | The third byte is the pressure in the brake system, in Bars. The 0.7 divider seems to be a good value to get 100% at pressure slightly higher than those you're likely to use on the track for cars with no aero. You can use 0.8 or 0.9 if you see 100% too often.
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??? | D | Always 0?
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### PID 0xD4 (212)
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Update frequency: 50 times per second.
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Channel name | Equation | Notes
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------------ | -------- | -----
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Wheel speed FL | `bytesToIntLe(raw, 0, 2) * 0.015694` | Use same multiplier as for speed in 0xD1
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Wheel speed FR | `bytesToIntLe(raw, 2, 2) * 0.015694` | Use same multiplier as for speed in 0xD1
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Wheel speed RL | `bytesToIntLe(raw, 4, 2) * 0.015694` | Use same multiplier as for speed in 0xD1
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Wheel speed RR | `bytesToIntLe(raw, 6, 2) * 0.015694` | Use same multiplier as for speed in 0xD1
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### PID 0x140 (320)
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Update frequency: 100 times per second.
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Channel name | Equation | Notes
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------------ | -------- | -----
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Accelerator position | `A / 2.55`
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Clutch position | `(B & 0x80) / 1.28` | On/off only
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??? | B & 0x70 | Unused?
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??? | B & 0x0f | 0–15 counter?
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Engine RPM | `bitsToUIntLe(raw, 16, 14)`
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??? | `D & 0x80` | Always 0?
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??? | `D & 0x40` | 1 when accelerator pedal is released, 0 otherwise
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Accelerator position | `E / 2.55` | Not clear what's the difference from the other two
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Accelerator position | `F / 2.55` | Not clear what's the difference from the other two
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Throttle position | `G / 2.55` | Not tested
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??? | H | Some flags
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### PID 0x141 (321)
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Update frequency: 100 times per second.
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Channel name | Equation | Notes
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------------ | -------- | -----
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Accelerator pedal position? | `bytesToIntLe(raw, 0, 2)` | Follows `A` from `0x140` closely with ~9860 for 0% and ~11625 for 42%. Needs more testing.
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Engine load? | `bytesToIntLe(raw, 2, 2)` | Follows the data from OBD PIDs 0x4 and 0x43 pretty well.
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Engine RPM | `bitsToUIntLe(raw, 32, 14)`
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??? | `F & 0x80` | 1 when accelerator pedal is released, 0 otherwise
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??? | `F & 0x40` | Always 0?
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Gear | `(G & 0xf) * (1 - (min(G & 0xf, 7)) / 7)` | It's basically just `G & 0xf` but neutral is reported as `7`, hence the complex math to turn it into a 0. The reverse gear is reported as `1`. The value can be wrong when the clutch pedal is depressed.
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??? | `G & 0xF0` | I saw values of 128, 160, 192 here.
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??? | `H` | Equals to 16 when I lift off the accelerator, then turns to 8, then 0.
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### PID 0x360 (864)
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Update frequency: 20 times per second.
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Channel name | Equation | Notes
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------------ | -------- | -----
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Engine oil temperature | `C - 40`
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Coolant temperature | `D - 40`
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Cruise control ON | `(F & 16) / 16` | Means the mode is "On", but not necessarily "Set". Not tested much.
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Cruise control set | `(F & 32) / 32` | Not tested much.
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Cruise control speed | `H` | In the same unit as the current speed display units? Not tested much.
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### PID 0x361 (865)
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Update frequency: 20 times per second.
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Channel name | Equation | Notes
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------------ | -------- | -----
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Gear | A & 0x7 | Not tested
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### Would be nice to find PIDs for ...
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TODO: would be great to find how to read the ambient temperature, and maybe the
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intake temperature.
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TODO: find how to log the fuel remaining.
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### Typical histogram of PIDs
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Here's what the distribution of PIDs looks like in the CAN bus while idling in a
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parking lot:
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PID | Decimal PID | Number of packets received over a 10 second period
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---- | --- | ---
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0x18 | 24 | 1000
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0xD0 | 208 | 500
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0xD1 | 209 | 500
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0xD2 | 210 | 500
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0xD3 | 211 | 500
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0xD4 | 212 | 500
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0x140 | 320 | 1000
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0x141 | 321 | 1000
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0x142 | 322 | 1000
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0x144 | 324 | 500
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0x152 | 338 | 500
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0x156 | 342 | 500
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0x280 | 640 | 500
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0x282 | 642 | 167
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0x284 | 644 | 100
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0x360 | 864 | 200
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0x361 | 865 | 200
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0x370 | 880 | 200
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0x372 | 882 | 100
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0x374 | 884 | 10
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0x375 | 885 | 10
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0x37A | 890 | 10
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0x3D1 | 977 | 84
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0x440 | 1088 | 25
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0x442 | 1090 | 25
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0x44D | 1101 | 25
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0x46C | 1132 | 25
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0x4C1 | 1217 | 10
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0x4C3 | 1219 | 10
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0x4C6 | 1222 | 10
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0x4C8 | 1224 | 10
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0x4DC | 1244 | 10
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0x4DD | 1245 | 10
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0x63B | 1595 | 20
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0x6E1 | 1761 | 10
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0x6E2 | 1762 | 10
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