GOODIX CONFIDENTIAL
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Timing for INT high-level wakeup:
e) Approach Mode
When the HotKnot function is enabled, GT911 is operating in Approach Mode. When GT911 exits Approach Mode,
the host can send command 0x20 or 0x21 to enable GT911 to enter Approach mode again. In this mode, touch
detection and near-field proximity detection alternate. If the host sends 0x21 to GT911, GT911 will work as a
transmitting terminal and transmit signals with a specified pattern and frequency via driving and sensing channels.
Then, GT911 detects whether there are feedback signals with the same specified pattern and frequency from the
receiving terminal. This helps to determine whether any receiving terminal exists. If the host sends 0x20 to GT911,
GT911 will work as a receiving terminal and detect signals with a specified pattern and frequency from the
transmitting terminal. If such a signal is detected, GT911 responds using signals with the specified pattern and
frequency to the transmitting terminal. In Approach mode, when detecting any communicable terminal within the
near-field range, GT911 will notify the host via INT to capture status. To ensure reliable detection between the
transmitting terminal and the receiving terminal, it is required to keep detecting for a minimum of 150ms after the
two terminals have detected each other. Then the host downloads and sends HotKnot transmission firmware to
enable GT911 to enter Receive mode.
f)
Receive Mode
When GT911 operates in Approach mode, after notified that GT911 has successfully detected another HotKnot
terminal, the host downloads and sends HotKnot transmission firmware to enable GT911 to enter Receive mode. In
Receive mode, GT911 continues to detect frame start signal, once the signal is detected, GT911 begins to detect
and receive data. When the receiving process is complete, GT911 verifies the data. If GT911 finds erroneous data,
the receiving process begins again. If the data is found to be correct, GT911 notifies the host via INT to read data in
the Receive Buffer.
g) Send Mode
When GT911 works in Receive mode, the host sends outgoing data to the Transmit Buffer. When detecting that the
Transmit Buffer is flushed and there is data to be sent, GT911 automatically switches from Receive mode to Send
mode. In Send mode, GT911 sends a frame start signal. If it detects ACK fed back from the receiving terminal, it
continues to send the data signal. After sending a data chunk, GT911 begins to detect ACK. If it does not detect any
ACK or if it detects an erroneous ACK, GT911 will resend the data chunk. If this resending fails over 5 times, it
will resend the current data frame another time to the receiving terminal until the host enables GT911 to exit Send
mode due to timeout. If GT911 detects ACK and sends the data successfully, it will automatically switch to
Receive mode after the host completes the data processing or due to timeout.
