GCBASIC documentation
Graphical LCD

Syntax:

    GLCD_Open_PageTransaction
      ....
        additional number of other GLCD methods
      ....
    GLCD_Close_PageTransaction

Explanation:

To make the operation of GLCD seamless - specific library supports GLCDTransaction.   GLCDTransaction automatically manages the methods to update the GLCD display via a RAM memory buffer, where this buffer can be small relative to the size of the total number of GLCD pixels.

The process of GLCDtransaction sends GLCD commands to the GLCD display on a page and page basis.   Each page is the size of the buffer and for a large GLCD display the number of pages may be equivilent to the numbers of pixels high (height).

GLCDTransaction simplies the operation by ensure the buffer is setup correctly, handles the GLCD appropiately, handles the sending of the buffer and then close out the update to the display.

To use GLCDTransaction use the followng methods.

    GLCD_Open_PageTransaction
      ....
      additional number of other GLCD methods
      ....
    GLCD_Close_PageTransaction

It recommended to use GLCDTransactions at all times when using the e-Paper libraries.   Other GLCD libraries support GLCDTransaction to reduce the memory requirement.  

Thes GLCDTransactions methods remove the complexity of the GLCD display update process when RAM within the microcontroller is limited.

When using GLCDTransaction you must commence with GLCD_Open_PageTransaction then a series of GLCD commands and then terminate with GLCD_Close_PageTransaction.

GLCDTransaction Insight: When using GLCDtransactions the number of buffer pages is probably be greater then 1 (unless using the SRAM option), so the process of incrementing variables and calls to non-GLCD methods must be considered carefully. The transaction process will increment variables and call non-GLCD methods the same number of times as the number of pages. Therefore, design GLCDTransaction operations with this is mind.

SRAM as the display buffer

To improve memory usage the e-paper the e-Paper libraries support the use of SRAM. SRAM can be used as an alternative to the microcontrollers RAM. Using SRAM does have a small performance impact but does free up the critical resource of the microcontroller RAM. The use of SRAM within the e-paper library is transparent to the user. To use SRAM as the e-paper buffer you will need to set-up the SRAM library. See the SRAM library for more details on SRAM usage.

When using SRAM for the e-paper buffer it is still remcommend to use GLCDTransaction as this ensure the SRAM buffer is correctly initialised.

Optional GLCD_Open_Transaction parameters

Syntax:

    GLCD_Open_PageTransaction ( low_page, high_page )

Explanation:

You can optionally pass GLCD_Open_PageTransaction two parmeters. The parameters will constrain the GLCD display update process to the specific pages.

This can be used when only updating a potion of the screen to improve performance.