Modbus - E-Paper 296x128 Bricklet

This is the description of the Modbus protocol for the E-Paper 296x128 Bricklet. General information and technical specifications for the E-Paper 296x128 Bricklet are summarized in its hardware description.

API

A general description of the Modbus protocol structure can be found here.

Basic Functions

BrickletEPaper296x128.draw
Function ID:1
Request:empty payload
Response:no response

Draws the current black/white and red or gray buffer to the e-paper display.

The Bricklet does not have any double-buffering. You should not call this function while writing to the buffer. See get_draw_status.

BrickletEPaper296x128.get_draw_status
Function ID:

2

Request:

empty payload

Response:
  • draw_status -- uint8

Returns one of three draw statuses:

  • Idle
  • Copying: Data is being copied from the buffer of the Bricklet to the buffer of the display.
  • Drawing: The display is updating its content (during this phase the flickering etc happens).

You can write to the buffer (through one of the write or draw functions) when the status is either idle or drawing. You should not write to the buffer while it is being copied to the display. There is no double-buffering.

The following meanings are defined for the parameters of this function:

  • 0: idle, for draw_status
  • 1: copying, for draw_status
  • 2: drawing, for draw_status
BrickletEPaper296x128.write_black_white_low_level
Function ID:

3

Request:
  • x_start -- uint16
  • y_start -- uint8
  • x_end -- uint16
  • y_end -- uint8
  • pixels_length -- uint16
  • pixels_chunk_offset -- uint16
  • pixels_chunk_data -- bool[432]
Response:

no response

Writes black/white pixels to the specified window into the buffer.

The x-axis goes from 0 to 295 and the y-axis from 0 to 127. The pixels are written into the window line by line top to bottom and each line is written from left to right.

The value 0 (false) corresponds to a black pixel and the value 1 (true) to a white pixel.

This function writes the pixels into the black/white pixel buffer, to draw the buffer to the display use draw.

Use write_color_low_level to write red or gray pixels.

BrickletEPaper296x128.read_black_white_low_level
Function ID:

4

Request:
  • x_start -- uint16
  • y_start -- uint8
  • x_end -- uint16
  • y_end -- uint8
Response:
  • pixels_length -- uint16
  • pixels_chunk_offset -- uint16
  • pixels_chunk_data -- bool[464]

Returns the current content of the black/white pixel buffer for the specified window.

The x-axis goes from 0 to 295 and the y-axis from 0 to 127. The pixels are written into the window line by line top to bottom and each line is written from left to right.

The current content of the buffer does not have to be the current content of the display. It is possible that the data was not drawn to the display yet and after a restart of the Bricklet the buffer will be reset to black, while the display retains its content.

BrickletEPaper296x128.write_color_low_level
Function ID:

5

Request:
  • x_start -- uint16
  • y_start -- uint8
  • x_end -- uint16
  • y_end -- uint8
  • pixels_length -- uint16
  • pixels_chunk_offset -- uint16
  • pixels_chunk_data -- bool[432]
Response:

no response

The E-Paper 296x128 Bricklet is available with the colors black/white/red and black/white/gray. Depending on the model this function writes either red or gray pixels to the specified window into the buffer.

The x-axis goes from 0 to 295 and the y-axis from 0 to 127. The pixels are written into the window line by line top to bottom and each line is written from left to right.

The value 0 (false) means that this pixel does not have color. It will be either black or white (see write_black_white_low_level). The value 1 (true) corresponds to a red or gray pixel, depending on the Bricklet model.

This function writes the pixels into the red or gray pixel buffer, to draw the buffer to the display use draw.

Use write_black_white_low_level to write black/white pixels.

BrickletEPaper296x128.read_color_low_level
Function ID:

6

Request:
  • x_start -- uint16
  • y_start -- uint8
  • x_end -- uint16
  • y_end -- uint8
Response:
  • pixels_length -- uint16
  • pixels_chunk_offset -- uint16
  • pixels_chunk_data -- bool[464]

Returns the current content of the red or gray pixel buffer for the specified window.

The x-axis goes from 0 to 295 and the y-axis from 0 to 127. The pixels are written into the window line by line top to bottom and each line is written from left to right.

The current content of the buffer does not have to be the current content of the display. It is possible that the data was not drawn to the display yet and after a restart of the Bricklet the buffer will be reset to black, while the display retains its content.

BrickletEPaper296x128.fill_display
Function ID:

7

Request:
  • color -- uint8
Response:

no response

Fills the complete content of the display with the given color.

The following meanings are defined for the parameters of this function:

  • 0: black, for color
  • 1: white, for color
  • 2: red, for color
  • 2: gray, for color
BrickletEPaper296x128.draw_text
Function ID:

8

Request:
  • position_x -- uint16
  • position_y -- uint8
  • font -- uint8
  • color -- uint8
  • orientation -- uint8
  • text -- char[50]
Response:

no response

Draws a text with up to 50 characters at the pixel position (x, y).

The x values have to be within the range of 0 to 295 and the y values have to be within the range of 0 to 127.

You can use one of 9 different font sizes and draw the text in black/white/red|gray. The text can be drawn horizontal or vertical.

The following meanings are defined for the parameters of this function:

  • 0: 6x8, for font
  • 1: 6x16, for font
  • 2: 6x24, for font
  • 3: 6x32, for font
  • 4: 12x16, for font
  • 5: 12x24, for font
  • 6: 12x32, for font
  • 7: 18x24, for font
  • 8: 18x32, for font
  • 9: 24x32, for font
  • 0: black, for color
  • 1: white, for color
  • 2: red, for color
  • 2: gray, for color
  • 0: horizontal, for orientation
  • 1: vertical, for orientation
BrickletEPaper296x128.draw_line
Function ID:

9

Request:
  • position_x_start -- uint16
  • position_y_start -- uint8
  • position_x_end -- uint16
  • position_y_end -- uint8
  • color -- uint8
Response:

no response

Draws a line from (x, y)-start to (x, y)-end in the given color. The x values have to be within the range of 0 to 295 and the y values have t be within the range of 0 to 127.

The following meanings are defined for the parameters of this function:

  • 0: black, for color
  • 1: white, for color
  • 2: red, for color
  • 2: gray, for color
BrickletEPaper296x128.draw_box
Function ID:

10

Request:
  • position_x_start -- uint16
  • position_y_start -- uint8
  • position_x_end -- uint16
  • position_y_end -- uint8
  • fill -- bool
  • color -- uint8
Response:

no response

Draws a box from (x, y)-start to (x, y)-end in the given color. The x values have to be within the range of 0 to 295 and the y values have to be within the range of 0 to 127.

If you set fill to true, the box will be filled with the color. Otherwise only the outline will be drawn.

The following meanings are defined for the parameters of this function:

  • 0: black, for color
  • 1: white, for color
  • 2: red, for color
  • 2: gray, for color

Advanced Functions

BrickletEPaper296x128.set_update_mode
Function ID:

12

Request:
  • update_mode -- uint8
Response:

no response

Note

The default update mode corresponds to the default e-paper display manufacturer settings. All of the other modes are experimental and will result in increased ghosting and possibly other long-term side effects.

If you want to know more about the inner workings of an e-paper display take a look at this excellent video from Ben Krasnow: https://www.youtube.com/watch?v=MsbiO8EAsGw.

If you are not sure about this option, leave the update mode at default.

Currently there are three update modes available:

  • Default: Settings as given by the manufacturer. An update will take about 7.5 seconds and during the update the screen will flicker several times.
  • Black/White: This will only update the black/white pixel. It uses the manufacturer settings for black/white and ignores the red or gray pixel buffer. With this mode the display will flicker once and it takes about 2.5 seconds. Compared to the default settings there is more ghosting.
  • Delta: This will only update the black/white pixel. It uses an aggressive method where the changes are not applied for a whole buffer but only for the delta between the last and the next buffer. With this mode the display will not flicker during an update and it takes about 900-950ms. Compared to the other two settings there is more ghosting. This mode can be used for something like a flicker-free live update of a text.

With the black/white/red display if you use either the black/white or the delta mode, after a while of going back and forth between black and white the white color will start to appear red-ish or pink-ish.

If you use the aggressive delta mode and rapidly change the content, we recommend that you change back to the default mode every few hours and in the default mode cycle between the three available colors a few times. This will get rid of the ghosting and after that you can go back to the delta mode with flicker-free updates.

The following meanings are defined for the parameters of this function:

  • 0: default, for update_mode
  • 1: black white, for update_mode
  • 2: delta, for update_mode
BrickletEPaper296x128.get_update_mode
Function ID:

13

Request:

empty payload

Response:
  • update_mode -- uint8

Returns the update mode as set by set_update_mode.

The following meanings are defined for the parameters of this function:

  • 0: default, for update_mode
  • 1: black white, for update_mode
  • 2: delta, for update_mode
BrickletEPaper296x128.set_display_type
Function ID:

14

Request:
  • display_type -- uint8
Response:

no response

Sets the type of the display. The e-paper display is available in black/white/red and black/white/gray. This will be factory set during the flashing and testing phase. The value is saved in non-volatile memory and will stay after a power cycle.

The following meanings are defined for the parameters of this function:

  • 0: black white red, for display_type
  • 1: black white gray, for display_type
BrickletEPaper296x128.get_display_type
Function ID:

15

Request:

empty payload

Response:
  • display_type -- uint8

Returns the type of the e-paper display. It can either be black/white/red or black/white/gray.

The following meanings are defined for the parameters of this function:

  • 0: black white red, for display_type
  • 1: black white gray, for display_type
BrickletEPaper296x128.get_spitfp_error_count
Function ID:

234

Request:

empty payload

Response:
  • error_count_ack_checksum -- uint32
  • error_count_message_checksum -- uint32
  • error_count_frame -- uint32
  • error_count_overflow -- uint32

Returns the error count for the communication between Brick and Bricklet.

The errors are divided into

  • ACK checksum errors,
  • message checksum errors,
  • framing errors and
  • overflow errors.

The errors counts are for errors that occur on the Bricklet side. All Bricks have a similar function that returns the errors on the Brick side.

BrickletEPaper296x128.set_bootloader_mode
Function ID:

235

Request:
  • mode -- uint8
Response:
  • status -- uint8

Sets the bootloader mode and returns the status after the requested mode change was instigated.

You can change from bootloader mode to firmware mode and vice versa. A change from bootloader mode to firmware mode will only take place if the entry function, device identifier and CRC are present and correct.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

The following meanings are defined for the parameters of this function:

  • 0: bootloader, for mode
  • 1: firmware, for mode
  • 2: bootloader wait for reboot, for mode
  • 3: firmware wait for reboot, for mode
  • 4: firmware wait for erase and reboot, for mode
  • 0: ok, for status
  • 1: invalid mode, for status
  • 2: no change, for status
  • 3: entry function not present, for status
  • 4: device identifier incorrect, for status
  • 5: crc mismatch, for status
BrickletEPaper296x128.get_bootloader_mode
Function ID:

236

Request:

empty payload

Response:
  • mode -- uint8

Returns the current bootloader mode, see set_bootloader_mode.

The following meanings are defined for the parameters of this function:

  • 0: bootloader, for mode
  • 1: firmware, for mode
  • 2: bootloader wait for reboot, for mode
  • 3: firmware wait for reboot, for mode
  • 4: firmware wait for erase and reboot, for mode
BrickletEPaper296x128.set_write_firmware_pointer
Function ID:

237

Request:
  • pointer -- uint32
Response:

no response

Sets the firmware pointer for write_firmware. The pointer has to be increased by chunks of size 64. The data is written to flash every 4 chunks (which equals to one page of size 256).

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

BrickletEPaper296x128.write_firmware
Function ID:

238

Request:
  • data -- uint8[64]
Response:
  • status -- uint8

Writes 64 Bytes of firmware at the position as written by set_write_firmware_pointer before. The firmware is written to flash every 4 chunks.

You can only write firmware in bootloader mode.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

BrickletEPaper296x128.set_status_led_config
Function ID:

239

Request:
  • config -- uint8
Response:

no response

Sets the status LED configuration. By default the LED shows communication traffic between Brick and Bricklet, it flickers once for every 10 received data packets.

You can also turn the LED permanently on/off or show a heartbeat.

If the Bricklet is in bootloader mode, the LED is will show heartbeat by default.

The following meanings are defined for the parameters of this function:

  • 0: off, for config
  • 1: on, for config
  • 2: show heartbeat, for config
  • 3: show status, for config
BrickletEPaper296x128.get_status_led_config
Function ID:

240

Request:

empty payload

Response:
  • config -- uint8

Returns the configuration as set by set_status_led_config

The following meanings are defined for the parameters of this function:

  • 0: off, for config
  • 1: on, for config
  • 2: show heartbeat, for config
  • 3: show status, for config
BrickletEPaper296x128.get_chip_temperature
Function ID:

242

Request:

empty payload

Response:
  • temperature -- int16

Returns the temperature in °C as measured inside the microcontroller. The value returned is not the ambient temperature!

The temperature is only proportional to the real temperature and it has bad accuracy. Practically it is only useful as an indicator for temperature changes.

BrickletEPaper296x128.reset
Function ID:243
Request:empty payload
Response:no response

Calling this function will reset the Bricklet. All configurations will be lost.

After a reset you have to create new device objects, calling functions on the existing ones will result in undefined behavior!

BrickletEPaper296x128.write_uid
Function ID:

248

Request:
  • uid -- uint32
Response:

no response

Writes a new UID into flash. If you want to set a new UID you have to decode the Base58 encoded UID string into an integer first.

We recommend that you use Brick Viewer to change the UID.

BrickletEPaper296x128.read_uid
Function ID:

249

Request:

empty payload

Response:
  • uid -- uint32

Returns the current UID as an integer. Encode as Base58 to get the usual string version.

BrickletEPaper296x128.get_identity
Function ID:

255

Request:

empty payload

Response:
  • uid -- char[8]
  • connected_uid -- char[8]
  • position -- char
  • hardware_version -- uint8[3]
  • firmware_version -- uint8[3]
  • device_identifier -- uint16

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' or 'd'.

The device identifier numbers can be found here

Callbacks

BrickletEPaper296x128.CALLBACK_DRAW_STATUS
Function ID:

11

Response:
  • draw_status -- uint8

Callback for the current draw status. Will be called every time the draw status changes (see get_draw_status).

The following meanings are defined for the parameters of this function:

  • 0: idle, for draw_status
  • 1: copying, for draw_status
  • 2: drawing, for draw_status