Concurrent Driving Method with Fast Scan Rate for Large Mutual Capacitance Touch Screens

Table 1

Proposed touch screen controller block function.

Block	Functions
CPU	(i) Run algorithm which is installed on the external flash memory or data memory; (ii) Feed control parameters to control registers block; (iii) Start TX/RX controller; (iv) Fill TX memory with TX signal sample values; (v) Read RX signal sample values from RX memory; (vi) Control UART and SPI blocks for data exchange with other chips or a host system
Host system interface	(i) Write the internal memories or control registers; (ii) Test and debug other blocks; (iii) Use the touch positions for host system applications
AHB bus	Connect CPU to other functional blocks
External memory controller	Connect external flash memory to work as program memory and SRAM memory to work as data memory
Data memory	Used as internal data memory. It can also be used as a program memory and data memory at the same time
RX memory; (2 modules)	(i) Two-port memory operating as a FIFO with one port connected to the AHB bus and the other to an ADC; (ii) Store TX output values sampled from the ADC, which is to be analyzed by the CPU; (iii) If one of the two memory blocks is storing RX samples, CPU is reading the other one. Once the memory is filled up, the two memories swap their roles
TX memory	(i) Two-port memory operating as a FIFO with one port connected to the AHB bus and the other to signal generator to feed signal values to DAC; (ii) CPU precalculates and stores signal samples into this memory block before initiating the TX/RX controller
Control registers	Register storing control parameters for TX/RX controller
ADC	Convert the analog RX signals sampled from sensing circuit
DAC	Convert digital TX values stored in DAC memory to analog values to be applied to TSP
TX/RX controller	Control all TX and RX switches, ADC, DAC, and TX driver. It sends synchronous control signals to all blocks based on the value of control registers
TX driver	Amplify the signal coming out from DAC to be applied to TSP. It also can set different gains using a control signal coming from TX/RX controller
Sensing circuit	Amplify the output signal coming from TSP and cancel the noise
Set of TX switches	Used to select active TX line/lines to apply TX signals
Set of RX switches	Used to select a RX pair to read out RX signal