Automating digital display
A device comprises a central processing unit (CPU), a display controller configured for controlling a digital display and a memory configured for storing data corresponding to the digital display. The device includes a direct memory access (DMA) controller configured for autonomously transferring the data from the memory directly to the display controller without CPU intervention.
1. A device comprising:
a display controller configured to control a digital display, wherein information presented on the digital display includes one or more symbols, a symbol comprising one or more segments that are atomic elements of the digital display and represented by one or more bitmaps;
a memory configured to store data corresponding to the digital display; and
a direct memory access (DMA) controller configured to autonomously transfer the data from the memory directly to the display controller without central processing unit (CPU) intervention, the DMA controller comprising an interface configured to stall a transfer until a ready signal is received from the display controller,
wherein the data included in a transfer is associated with a bitmap corresponding to a symbol, the bitmap including information on states of one or more segments comprising the symbol, an offset in display memory indicating a subset of the one or more segments addressed by the bitmap and a bit mask indicating segments in the subset that are to be updated, and wherein the state of a segment indicates whether the respective segment is displayed on or displayed off.
2. The device of claim 1 , further comprising a CPU connected to the display controller, wherein the CPU is configured to be idle or performing an activity unrelated to the digital display at a time when the DMA controller is transferring the data from the memory to the display controller.
3. The device of claim 1 , wherein the digital display includes a Liquid Crystal Display (LCD), and wherein the display controller includes an LCD controller.
4. The device of claim 1 , further comprising the display memory that includes a bank of registers with each register associated with a segment, and wherein the offset is used for selecting a subset of the registers and the bit mask is used for determining which of the subset of the registers will be updated.
5. The device of claim 1 , wherein a size of the offset ranges from a bit to a byte.
6. The device of claim 1 , wherein a number of DMA transfers from the memory to the display controller corresponding to a symbol is based on a size of the symbol and an arrangement of one or more segments included in the symbol.
7. The device of claim 1 , wherein the display controller is configured to perform operations comprising:
measuring an amount of time using an internal counter;
determining whether the measured amount of time has exceeded a threshold time value;
based on determining that the measured amount of time has exceeded the threshold time value, sending a ready signal to the DMA controller;
receiving an amount of data from the DMA controller; and
presenting, on the digital display, information corresponding to the amount of data received from the DMA controller.
8. The device of claim 7 , wherein the threshold time value corresponds to a display rate of the digital display.
9. The device of claim 7 , wherein the DMA controller is configured to perform operations comprising:
receiving the ready signal from the display controller; and
responsive to receiving the ready signal from the display controller, transferring the amount of data in a transfer cycle.
10. The device of claim 9 , wherein the DMA controller is configured to receive a ready signal from additional peripheral controllers.
11. The device of claim 9 , wherein the amount of data transferred in a transfer cycle is based on a size of a DMA data bus that is used for the transfer.
12. The device of claim 1 , wherein the DMA controller is configured to transfer a total amount of data to be presented on the digital display in multiple transfer cycles when the total amount of data is greater than the amount transferred in a transfer cycle.
13. The device of claim 1 , wherein the digital display is configured to present a string of characters that includes an ASCII character, and wherein the data included in a transfer corresponds to the ASCII character.
14. The device of claim 13 , wherein the display controller includes look-up tables and is configured to translate the data corresponding to the ASCII character to a bitmap for the digital display using the look-up tables.
15. The device of claim 1 , wherein the digital display is configured to present a string of characters using a sequential mode or a scrolling mode, and wherein the display controller is configured to perform operations comprising:
determining whether the display mode is the sequential mode or the scrolling mode; and
based on determining that the display mode is the sequential mode, displaying characters comprising a subset of the string, the characters included in a displayed subset being in sequence with the characters included in preceding displayed subsets.
16. The device of claim 1 , wherein the digital display is configured to present a string of characters using a sequential mode or a scrolling mode, and wherein the display controller is configured to perform operations comprising:
determining whether the display mode is the sequential mode or the scrolling mode;
based on determining that the display mode is the scrolling mode, checking a number of steps into which the digital display is divided, the number of steps based on a length of the string of characters and a size of the digital display; and
repeating a display of the string of characters a number of times that is same as the number of steps.
17. The device of claim 16 , wherein information on the number of steps is included in a configuration register associated with the display controller.
18. The device of claim 1 , wherein the digital display is configured to present a string of characters using a sequential mode or a scrolling mode, and wherein the display controller is configured to perform operations comprising:
determining that the display mode is the scrolling mode;
obtaining a number of steps into which the digital display is divided, the number of steps based on a length of the string of characters and a size of the digital display; and
displaying successive sets of characters associated with the string, with each set repeating characters from the preceding set excluding an initial character included in the preceding set, wherein a number of the successive sets is same as the number of steps.
19. The device of claim 18 , wherein a size of each set is based on a size of the digital display.
20. A system comprising:
a display controller configured to control a digital display, wherein information presented on the digital display includes one or more symbols, a symbol comprising one or more segments that are atomic elements of the digital display;
a memory configured to store data corresponding to the digital display; and
a direct memory access (DMA) controller configured to autonomously transfer the data from the memory directly to the display controller without central processing unit (CPU) intervention, the DMA controller comprising an interface configured to stall a transfer until a ready signal is received from the display controller,
wherein the data included in a transfer includes information associated with a symbol, and wherein a number of transfers from the memory to the display controller corresponding to a symbol is based on a size of the symbol and an arrangement of one or more segments included in the symbol.
21. The system of claim 20 , further comprising a CPU connected to the display controller, wherein the CPU is configured to be idle or performing an activity unrelated to the digital display at a time when the DMA controller is transferring the data from the memory to the display controller.
22. The system of claim 20 , wherein the display controller is configured to perform operations comprising:
measuring an amount of time using an internal counter;
determining whether the measured amount of time has exceeded a threshold time value;
based on determining that the measured amount of time has exceeded the threshold time value, sending a ready signal to the DMA controller;
receiving an amount of data from the DMA controller; and
presenting, on the digital display, information corresponding to the amount of data received from the DMA controller.