Designing a Low-Cost USB Mouse with the Cypress Semiconductor ...
Designing a Low-Cost USB Mouse with the Cypress Semiconductor ...
Designing a Low-Cost USB Mouse with the Cypress Semiconductor ...
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<strong>Designing</strong> a <strong>Low</strong>-<strong>Cost</strong> <strong>USB</strong> <strong>Mouse</strong><br />
Endpoint_1<br />
• Prepare data in Endpoint_1 DMA<br />
buffer<br />
• Re-enable interrupts<br />
Return<br />
Figure 13. Endpoint 1 Interrupt Service Routine<br />
lh = left horizontal photo transistor<br />
rh = right horizontal photo transistor<br />
r/l = right / left bit state<br />
r/l=0 0<br />
lh=0<br />
STATE 0<br />
rh=0<br />
r/l=01<br />
STATE 1<br />
rh=01<br />
lh=1 rh=1<br />
rh=10 lh=10<br />
STATE 3<br />
lh=01<br />
STATE 2<br />
r/l=10<br />
r/l=11<br />
Figure 14. <strong>Mouse</strong> State Diagram<br />
State 3 State 2 State 0 State 1 State 3<br />
Left horizontal<br />
photo transistor output<br />
Right horizontal<br />
photo transistor output<br />
Left movement Right movement<br />
Figure 15. State Definitions<br />
7
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