This is the description of the Delphi/Lazarus API bindings for the CAN Bricklet. General information and technical specifications for the CAN Bricklet are summarized in its hardware description.
An installation guide for the Delphi/Lazarus API bindings is part of their general description.
The example code below is Public Domain (CC0 1.0).
Download (ExampleLoopback.pas)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 | program ExampleLoopback;
{$ifdef MSWINDOWS}{$apptype CONSOLE}{$endif}
{$ifdef FPC}{$mode OBJFPC}{$H+}{$endif}
uses
SysUtils, IPConnection, BrickletCAN;
type
TExample = class
private
ipcon: TIPConnection;
can: TBrickletCAN;
public
procedure FrameReadCB(sender: TBrickletCAN; const frameType: byte;
const identifier: longword; const data: TArray0To7OfUInt8;
const length_: byte);
procedure Execute;
end;
const
HOST = 'localhost';
PORT = 4223;
UID = 'XYZ'; { Change XYZ to the UID of your CAN Bricklet }
var
e: TExample;
{ Callback procedure for frame read callback }
procedure TExample.FrameReadCB(sender: TBrickletCAN; const frameType: byte;
const identifier: longword; const data: TArray0To7OfUInt8;
const length_: byte);
var i: integer;
begin
if (frameType = BRICKLET_CAN_FRAME_TYPE_STANDARD_DATA) then begin
WriteLn('Frame Type: Standard Data');
end
else if (frameType = BRICKLET_CAN_FRAME_TYPE_STANDARD_REMOTE) then begin
WriteLn('Frame Type: Standard Remote');
end
else if (frameType = BRICKLET_CAN_FRAME_TYPE_EXTENDED_DATA) then begin
WriteLn('Frame Type: Extended Data');
end
else if (frameType = BRICKLET_CAN_FRAME_TYPE_EXTENDED_REMOTE) then begin
WriteLn('Frame Type: Extended Remote');
end;
WriteLn(Format('Identifier: %d', [identifier]));
Write(Format('Data (Length: %d):', [length_]));
for i := 0 to (length_ - 1) do begin
if i < 8 then begin
Write(Format(' %d', [data[i]]));
end;
end;
WriteLn('');
WriteLn('');
end;
procedure TExample.Execute;
var data: TArray0To7OfUInt8;
begin
{ Create IP connection }
ipcon := TIPConnection.Create;
{ Create device object }
can := TBrickletCAN.Create(UID, ipcon);
{ Connect to brickd }
ipcon.Connect(HOST, PORT);
{ Don't use device before ipcon is connected }
{ Configure transceiver for loopback mode }
can.SetConfiguration(BRICKLET_CAN_BAUD_RATE_1000KBPS,
BRICKLET_CAN_TRANSCEIVER_MODE_LOOPBACK, 0);
{ Register frame read callback to procedure FrameReadCB }
can.OnFrameRead := {$ifdef FPC}@{$endif}FrameReadCB;
{ Enable frame read callback }
can.EnableFrameReadCallback;
{ Write standard data frame with identifier 1742 and 3 bytes of data }
data[0] := 42; data[1] := 23; data[2] := 17;
can.WriteFrame(BRICKLET_CAN_FRAME_TYPE_STANDARD_DATA, 1742, data, 3);
WriteLn('Press key to exit');
ReadLn;
can.DisableFrameReadCallback;
ipcon.Destroy; { Calls ipcon.Disconnect internally }
end;
begin
e := TExample.Create;
e.Execute;
e.Destroy;
end.
|
Since Delphi does not support multiple return values directly, we use the
out
keyword to return multiple values from a function.
All functions and procedures listed below are thread-safe.
TBrickletCAN.
Create
(const uid: string; ipcon: TIPConnection)¶Parameters: |
|
---|---|
Returns: |
|
Creates an object with the unique device ID uid
:
can := TBrickletCAN.Create('YOUR_DEVICE_UID', ipcon);
This object can then be used after the IP Connection is connected.
TBrickletCAN.
WriteFrame
(const frameType: byte; const identifier: longword; const data: array [0..7] of byte; const length: byte): boolean¶Parameters: |
|
---|---|
Returns: |
|
Writes a data or remote frame to the write buffer to be transmitted over the CAN transceiver.
The Bricklet supports the standard 11-bit (CAN 2.0A) and the additional extended
18-bit (CAN 2.0B) identifiers. For standard frames the Bricklet uses bit 0 to 10
from the identifier
parameter as standard 11-bit identifier. For extended
frames the Bricklet additionally uses bit 11 to 28 from the identifier
parameter as extended 18-bit identifier.
For remote frames the data
parameter is ignored.
Returns true if the frame was successfully added to the write buffer. Returns false if the frame could not be added because write buffer is already full.
The write buffer can overflow if frames are written to it at a higher rate
than the Bricklet can transmitted them over the CAN transceiver. This may
happen if the CAN transceiver is configured as read-only or is using a low baud
rate (see SetConfiguration
). It can also happen if the CAN bus is
congested and the frame cannot be transmitted because it constantly loses
arbitration or because the CAN transceiver is currently disabled due to a high
write error level (see GetErrorLog
).
The following constants are available for this function:
For frameType:
TBrickletCAN.
ReadFrame
(out success: boolean; out frameType: byte; out identifier: longword; out data: array [0..7] of byte; out length: byte)¶Output Parameters: |
|
---|
Tries to read the next data or remote frame from the read buffer and return it.
If a frame was successfully read, then the success
return value is set to
true and the other return values contain the frame. If the read buffer is
empty and no frame could be read, then the success
return value is set to
false and the other return values contain invalid data.
The identifier
return value follows the identifier format described for
WriteFrame
.
For remote frames the data
return value always contains invalid data.
A configurable read filter can be used to define which frames should be
received by the CAN transceiver and put into the read buffer (see
SetReadFilter
).
Instead of polling with this function, you can also use callbacks. See the
EnableFrameReadCallback
function and the OnFrameRead
callback.
The following constants are available for this function:
For frameType:
TBrickletCAN.
SetConfiguration
(const baudRate: byte; const transceiverMode: byte; const writeTimeout: longint)¶Parameters: |
|
---|
Sets the configuration for the CAN bus communication.
The baud rate can be configured in steps between 10 and 1000 kbit/s.
The CAN transceiver has three different modes:
The write timeout has three different modes that define how a failed frame transmission should be handled:
The following constants are available for this function:
For baudRate:
For transceiverMode:
TBrickletCAN.
GetConfiguration
(out baudRate: byte; out transceiverMode: byte; out writeTimeout: longint)¶Output Parameters: |
|
---|
Returns the configuration as set by SetConfiguration
.
The following constants are available for this function:
For baudRate:
For transceiverMode:
TBrickletCAN.
SetReadFilter
(const mode: byte; const mask: longword; const filter1: longword; const filter2: longword)¶Parameters: |
|
---|
Set the read filter configuration. This can be used to define which frames should be received by the CAN transceiver and put into the read buffer.
The read filter has five different modes that define if and how the mask and the two filters are applied:
The mask and filters are used as bit masks. Their usage depends on the mode:
The mask and filters are applied in this way: The mask is used to select the identifier and data bits that should be compared to the corresponding filter bits. All unselected bits are automatically accepted. All selected bits have to match one of the filters to be accepted. If all bits for the selected mode are accepted then the frame is accepted and is added to the read buffer.
Mask Bit | Filter Bit | Identifier/Data Bit | Result |
---|---|---|---|
0 | X | X | Accept |
1 | 0 | 0 | Accept |
1 | 0 | 1 | Reject |
1 | 1 | 0 | Reject |
1 | 1 | 1 | Accept |
For example, to receive standard frames with identifier 0x123 only the mode can be set to Match-Standard with 0x7FF as mask and 0x123 as filter 1 and filter 2. The mask of 0x7FF selects all 11 identifier bits for matching so that the identifier has to be exactly 0x123 to be accepted.
To accept identifier 0x123 and identifier 0x456 at the same time, just set filter 2 to 0x456 and keep mask and filter 1 unchanged.
The following constants are available for this function:
For mode:
TBrickletCAN.
GetReadFilter
(out mode: byte; out mask: longword; out filter1: longword; out filter2: longword)¶Output Parameters: |
|
---|
Returns the read filter as set by SetReadFilter
.
The following constants are available for this function:
For mode:
TBrickletCAN.
GetErrorLog
(out writeErrorLevel: byte; out readErrorLevel: byte; out transceiverDisabled: boolean; out writeTimeoutCount: longword; out readRegisterOverflowCount: longword; out readBufferOverflowCount: longword)¶Output Parameters: |
|
---|
Returns information about different kinds of errors.
The write and read error levels indicate the current level of checksum, acknowledgement, form, bit and stuffing errors during CAN bus write and read operations.
When the write error level exceeds 255 then the CAN transceiver gets disabled and no frames can be transmitted or received anymore. The CAN transceiver will automatically be activated again after the CAN bus is idle for a while.
The write and read error levels are not available in read-only transceiver mode
(see SetConfiguration
) and are reset to 0 as a side effect of changing
the configuration or the read filter.
The write timeout, read register and buffer overflow counts represents the number of these errors:
SetConfiguration
).SetReadFilter
) can help to reduce the amount of received frames.
This count is not exact, but a lower bound, because the Bricklet might not
able detect all overflows if they occur in rapid succession.ReadFrame
function. Using the OnFrameRead
callback ensures that the read buffer
can not overflow.TBrickletCAN.
GetIdentity
(out uid: string; out connectedUid: string; out position: char; out hardwareVersion: array [0..2] of byte; out firmwareVersion: array [0..2] of byte; out deviceIdentifier: word)¶Output Parameters: |
|
---|
Returns the UID, the UID where the Bricklet is connected to, the position, the hardware and firmware version as well as the device identifier.
The position can be 'a', 'b', 'c', 'd', 'e', 'f', 'g' or 'h' (Bricklet Port). A Bricklet connected to an Isolator Bricklet is always at position 'z'.
The device identifier numbers can be found here. There is also a constant for the device identifier of this Bricklet.
TBrickletCAN.
EnableFrameReadCallback
¶Enables the OnFrameRead
callback.
By default the callback is disabled. Enabling this callback will disable the OnFrameReadable
callback.
TBrickletCAN.
DisableFrameReadCallback
¶Disables the OnFrameRead
callback.
By default the callback is disabled.
TBrickletCAN.
IsFrameReadCallbackEnabled
: boolean¶Returns: |
|
---|
Returns true if the OnFrameRead
callback is enabled, false otherwise.
TBrickletCAN.
SetFrameReadableCallbackConfiguration
(const enabled: boolean)¶Parameters: |
|
---|
Enables/disables the OnFrameReadable
callback.
By default the callback is disabled. Enabling this callback will disable the OnFrameRead
callback.
New in version 2.0.1 (Plugin).
TBrickletCAN.
GetFrameReadableCallbackConfiguration
: boolean¶Returns: |
|
---|
Returns true if the OnFrameReadable
callback is enabled, false otherwise.
New in version 2.0.1 (Plugin).
Callbacks can be registered to receive time critical or recurring data from the device. The registration is done by assigning a procedure to an callback property of the device object:
procedure TExample.MyCallback(sender: TBrickletCAN; const value: longint); begin WriteLn(Format('Value: %d', [value])); end; can.OnExample := {$ifdef FPC}@{$endif}example.MyCallback;
The available callback properties and their parameter types are described below.
Note
Using callbacks for recurring events is always preferred compared to using getters. It will use less USB bandwidth and the latency will be a lot better, since there is no round trip time.
TBrickletCAN.
OnFrameRead
¶procedure(sender: TBrickletCAN; const frameType: byte; const identifier: longword; const data: array [0..7] of byte; const length: byte) of object;
Callback Parameters: |
|
---|
This callback is triggered if a data or remote frame was received by the CAN transceiver.
The identifier
return value follows the identifier format described for
WriteFrame
.
For remote frames the data
return value always contains invalid values.
A configurable read filter can be used to define which frames should be
received by the CAN transceiver at all (see SetReadFilter
).
To enable this callback, use EnableFrameReadCallback
.
The following constants are available for this function:
For frameType:
TBrickletCAN.
OnFrameReadable
¶procedure(sender: TBrickletCAN) of object;
Callback Parameters: |
|
---|
This callback is triggered if a data or remote frame was received by the CAN
transceiver. The received frame can be read with ReadFrame
.
If additional frames are received, but ReadFrame
was not called yet, the callback
will not trigger again.
A configurable read filter can be used to define which frames should be
received by the CAN transceiver and put into the read queue (see
SetReadFilter
).
To enable this callback, use SetFrameReadableCallbackConfiguration
.
New in version 2.0.1 (Plugin).
Virtual functions don't communicate with the device itself, but operate only on the API bindings device object. They can be called without the corresponding IP Connection object being connected.
TBrickletCAN.
GetAPIVersion
: array [0..2] of byte¶Output Parameters: |
|
---|
Returns the version of the API definition implemented by this API bindings. This is neither the release version of this API bindings nor does it tell you anything about the represented Brick or Bricklet.
TBrickletCAN.
GetResponseExpected
(const functionId: byte): boolean¶Parameters: |
|
---|---|
Returns: |
|
Returns the response expected flag for the function specified by the function ID parameter. It is true if the function is expected to send a response, false otherwise.
For getter functions this is enabled by default and cannot be disabled,
because those functions will always send a response. For callback configuration
functions it is enabled by default too, but can be disabled by
SetResponseExpected
. For setter functions it is disabled by default
and can be enabled.
Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is sent and errors are silently ignored, because they cannot be detected.
The following constants are available for this function:
For functionId:
TBrickletCAN.
SetResponseExpected
(const functionId: byte; const responseExpected: boolean)¶Parameters: |
|
---|
Changes the response expected flag of the function specified by the function ID parameter. This flag can only be changed for setter (default value: false) and callback configuration functions (default value: true). For getter functions it is always enabled.
Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is sent and errors are silently ignored, because they cannot be detected.
The following constants are available for this function:
For functionId:
TBrickletCAN.
SetResponseExpectedAll
(const responseExpected: boolean)¶Parameters: |
|
---|
Changes the response expected flag for all setter and callback configuration functions of this device at once.
BRICKLET_CAN_DEVICE_IDENTIFIER
¶This constant is used to identify a CAN Bricklet.
The GetIdentity
function and the
TIPConnection.OnEnumerate
callback of the IP Connection have a deviceIdentifier
parameter to specify
the Brick's or Bricklet's type.
BRICKLET_CAN_DEVICE_DISPLAY_NAME
¶This constant represents the human readable name of a CAN Bricklet.