If the checksum or fresh flag is incorrect, the firmware will ignore configuration changes and revert to defaults.
: Sequential, repeating 8-byte point blocks dedicated to tracking Touch Point 2 through Touch Point 5. Initialization & Configuration Writing
For developers, the register map is the primary tool for solving common hardware hurdles:
Send the 16-bit register address (high byte then low byte) followed by the data bytes. gt911 register map
track_id (0), x_low (1), x_high (2), y_low (3), y_high (4), point_size_low (5), point_size_high (6), reserved (7) Identical 8-byte layout Point 3 Identical 8-byte layout Point 4 Identical 8-byte layout Point 5 Identical 8-byte layout Step-by-Step Implementation Guide Step 1: Initializing the I2C Address
This efficient method wakes the host only when a touch occurs.
A read/write area used to set touch thresholds, resolution, and sensor behavior. Coordinate/Status Data (0x814E and above): If the checksum or fresh flag is incorrect,
bit7 indicates if data is ready to be read; lower bits show the number of touch points. Point 1 X-Low
: This is the master control register. Writing specific values here triggers key actions:
A write-only register used to trigger immediate actions like reading coordinates, entering screen-off mode, or performing calibrations. Configuration Information (0x8047 – 0x8100): track_id (0), x_low (1), x_high (2), y_low (3),
For each point, calculate coordinates using bitwise operations:
Unlike standard I2C sensors that utilize 8-bit registers, the GT911 implements a . When initiating a transaction, the host must transmit the high byte ( Register_H ) first, followed by the low byte ( Register_L ). Memory Map Architecture Overview
The GT911 tracks up to 5 points sequentially. Each touch point occupies a fixed 7-byte block. Addresses 0x8150 to 0x8156 Touch Point 2: Addresses 0x8157 to 0x815D Touch Point 3: Addresses 0x815E to 0x8164 Touch Point 4: Addresses 0x8165 to 0x816B Touch Point 5: Addresses 0x816C to 0x8172 Inside a 7-Byte Touch Point Block (Example: Point 1) Relative Offset Register Address Field Name Description 0x8150 Unique ID assigned to this specific touch event 0x8151 X Coordinate Low Lower 8 bits of the X coordinate 0x8152 X Coordinate High Upper 8 bits of the X coordinate 0x8153 Y Coordinate Low Lower 8 bits of the Y coordinate 0x8154 Y Coordinate High Upper 8 bits of the Y coordinate 0x8155 Point Size Low Lower 8 bits of the contact area size 0x8156 Point Size High Upper 8 bits of the contact area size
X=(High Byte≪8)|Low ByteX equals open paren High Byte is much less than 8 close paren vertical line Low Byte