diff options
| -rw-r--r-- | doc/datafmt/datafmt.ms | 143 |
1 files changed, 106 insertions, 37 deletions
diff --git a/doc/datafmt/datafmt.ms b/doc/datafmt/datafmt.ms index 5ed643b..f218eae 100644 --- a/doc/datafmt/datafmt.ms +++ b/doc/datafmt/datafmt.ms @@ -1,5 +1,5 @@ .TL -Data Frame Format for the CAN Gauge Interface +Frame Format for the CAN Gauge Interface .AU Sam Anthony .AI @@ -9,9 +9,9 @@ The Gauge Interface receives .[ dbc07 .] -from other nodes in the vehicle via the CAN bus. +from other nodes via the vehicle's CAN bus. It also accepts frames from a host PC for calibration. -The format of these calibration, or +The formats of these calibration, or .I control , frames are the subject of this document. .NH 1 @@ -32,11 +32,14 @@ Analog 3 .IP \n+[step]. Analog 4 .LP -Each of these signals has an associated CAN ID and a calibration table; thus, there are 6 IDs and 6 tables. -The Interface listens for these IDs and uses the tables to lookup output signal values to drive he gauges. +Each of these signals has an associated CAN ID, encoding specification, and calibration table. +A signal's CAN ID specifies which message contains the signal. +It's encoding specification defines how the signal is encoded in the message's DATA FIELD. +And it's calibration field defines a mapping from the raw signal value extracted from the message to an output value that is used to generate a waveform to display the signal on a gauge. +.PP Each table has 32 rows, each of which contains a key and a value. -The keys and values are each 32-bit unsigned integers. -Numbers are transmitted in big-endian order in frames' DATA FIELD. +The keys and values are 32-bit and 16-bit respectively. +Numbers are transmitted in big-endian order in frames' DATA FIELDs. .NH 1 Frames .LP @@ -45,12 +48,12 @@ In addition to the signal-carrying frames, there are also two types of frame: .B "Table Control" , and -.B "ID Control" . +.B "Signal Control" . .NH 2 Table Control Frame .LP The Table Control Frame is used to read and write rows of the calibration tables. -It is an extended frame with DLC=8. +It is an extended frame with DLC=6. It may be either a DATA FRAME: to write to a table\(emor a REMOTE FRAME: to read from a table. .PP The Table Control Frame has extended ID @@ -73,7 +76,7 @@ Table Control ID .end .LP The DATA FIELD contains a row of the table. -The row is composed of two 32-bit unsigned integers: a key and a value. +The row is composed of a 32-bit integer and a 16-bit integer: a key and a value. They are transmitted in big-endian order. .begin dformat style bitwid 0.07 @@ -85,23 +88,24 @@ Table Control DATA FIELD 7-0 D3 7-0 D4 7-0 D5 - 7-0 D6 - 7-0 D7 noname 31-0 Key - 31-0 Val + 15-0 Val .end .LP Upon receiving a Table Control DATA FRAME, the Interface will write the key and value to the row of the table specified in the ID. .PP In the case of a REMOTE FRAME, the Interface will read the row of the table specified in the ID, and respond with a DATA FRAME containing the key and value of the row. .NH 2 -ID Control Frame +Signal Control Frame .LP -The ID Control Frame is used to read or modify the CAN ID associated with one of the 6 signals. -It is an extended frame with DLC=8. +The Signal Control Frame is used to read or modify the CAN ID associated with one of the signals, as well as to read or modify the signal's encoding format. +It is an extended frame with DLC=7. It may be either a DATA FRAME: to modify\(emor a REMOTE FRAME: to read. .PP +Upon receiving a Signal Control DATA FRAME, the Interface will write the signal's new ID and encoding to the EEPROM. +Upon receiving a Signal Control REMOTE FRAME, the Interface will respond with a DATA FRAME containing the signal's ID and encoding which were retrieved from the EEPROM. +.PP The ID Control Frame has extended ID .B 127210Xh . The least significant nibble, @@ -109,37 +113,102 @@ The least significant nibble, indicates one of the 6 signals [0, 5]. .begin dformat style bitwid 0.15 -ID Control ID +Signal Control ID 28-4 127210h 3-0 X .end .LP -The DATA FIELD contains the CAN ID of the signal specified in -.I X . -It may be either a standard or an extended ID. -In the case of a standard 11-bit ID, DLC=2 and the ID is sent as a 16-bit number. -In the case of an extended 29-bit ID, DLC=4 and the ID is sent as a 32-bit number. -The numbers are sent big-endian in both cases. -DLC can be used to determine whether the ID is standard or extended. -.begin dformat -style bitwid 0.08 -style recspread 0 -ID Control DATA FIELD (11-bit Std. ID) - 7-0 D0 - 7-0 D1 -noname - 15-11 - 10-0 Std. ID -.end +The DATA FIELD contains the signal's CAN ID and encoding format. .begin dformat style bitwid 0.08 style recspread 0 -ID Control DATA FIELD (29-bit Ext. ID) +Signal Control DATA FIELD 7-0 D0 7-0 D1 7-0 D2 7-0 D3 + 7-0 D4 + 7-0 D5 + 7-0 D6 noname - 31-29 - 28-0 Ext. ID + 31-0 SigId + 23-0 Encoding +noname + 31 EXIDE + 30-29 Empty + 28-0 ID + 7-0 Start + 7-0 Size + 7 Order + 6 Sign + 5-0 Empty .end +.LP +The signal's CAN ID is sent as a big-endian 32-bit integer in the +.I SigId +field. +The MSb\(embit 31, called +.I EXIDE \(em +indicates whether the ID is standard or extended. +.TS +tab(&); +Ci +L L. +EXIDE += 0 & Standard identifier += 1 & Extended identifier +.TE +The lower 11 or 29 bits hold the ID itself, depending on whether it is standard or extended. +In the case of a standard ID, +.I EXIDE =0 +and the ID is sent in the lower 11 bits of +.I SigId . +In the case of an extended ID, +.I EXIDE =1 +and the ID is sent in the lower 29 bits of +.I SigId . +.PP +The signal encoding defines how the signal's raw value is encoded in the message that carries it. +The encoding is sent in the +.I Encoding +field of the Signal Control Frame's DATA FIELD. +.LP +.I Start +specifies the position of the signal within the DATA FIELD of the message. +It corresponds to +.CW start_bit +in DBC. +.PP +.I Size +specifies the size of the signal in bits. +It corresponds to +.CW signal_size +in DBC. +.PP +.I Order +specifies the signal's byte order. +It corresponds to +.CW byte_order +in DBC. +.TS +tab(&); +Ci +L L. +Order += 0 & Little-endian += 1 & Big-endian +.TE +.LP +.I Sign +specifies the signal as being of type unsigned or signed. +It corresponds to +.CW value_type +in DBC. +.TS +tab(&); +Ci +L L. +Sign += 0 & Unsigned += 1 & Signed +.TE |