Detection system and methods
Various techniques are provided to facilitate a detection system to detect a presence of an externally coupled receiver device, such as a universal serial bus (USB) device. In one example, the system generates a reference current and passes the reference current via a conductor to a shared buffer circuit. The shared buffer circuit is adapted to selectively pass the reference current or a communication signal to the externally coupled receiver device. The system switches between a detect mode where the reference current is provided to the externally coupled receiver device and between a communicate mode where the reference current is blocked and the communication signal is provided to the externally coupled receiver device. The system monitors a voltage value of the conductor and the system monitors a time for the voltage value to reach a pre-determined threshold value in response to the reference current. The system detects a presence of the externally coupled receiver device based on the monitored time.
1. A method of detecting a presence of an externally coupled receiver device, the method comprising:
generating a reference current;
passing the reference current via a conductor to a shared buffer circuit, wherein the shared buffer circuit is operable to selectively pass the reference current or a communication signal to the externally coupled receiver device;
switching between a detect mode where the reference current is provided to the externally coupled receiver device and between a communicate mode where the reference current is blocked and the communication signal is provided to the externally coupled receiver device;
monitoring a voltage value of the conductor and a time for the voltage value to reach a pre-determined threshold value in response to the reference current; and
detecting a presence of the externally coupled receiver device based on the monitored time, wherein the voltage value rises slower when the externally coupled receiver device is connected and enabled to receive the communication signal than when the externally coupled receiver device is not connected or is not enabled to receive the communication signal.
2. The method of claim 1 , wherein the reference current is fed to a resistor and capacitor connected in series with a ground potential in the externally coupled receiver when the externally coupled receiver is enabled.
3. The method of claim 1 , wherein the step of detecting a presence of the externally coupled receiver device is based on the determination whether the voltage value reaches the threshold value in a time greater than approximately 200 micro seconds.
4. The method of claim 1 , further comprising coupling the receiver device externally via a serial bus to a host device.
5. The method of claim 4 , wherein the serial bus comprises two complementary data lines which are AC coupled in the externally coupled receiver device.
6. The method of claim 1 , further comprising splitting the reference current into a pair of reference currents and passing the pair of reference currents to the externally coupled receiver device.
7. The method of claim 1 , wherein the communication signal is a differential communication signal.
8. The method of claim 1 , further comprising interrupting power to the shared buffer circuit during the detect mode.
9. A detection circuit device operable to detect a presence of an externally coupled receiver device, the detection circuit device comprising:
a transmitter circuit operable to generate a reference current;
a shared buffer circuit operable to receive the reference current via a conductor, the shared buffer circuit also configured to selectively pass the reference current or a communication signal to the externally coupled receiver device, wherein the shared buffer circuit is further configured to switch between a detect mode where the reference current is provided to the externally coupled receiver device and between a communicate mode where the reference current is blocked and the communication signal is provided to the externally coupled receiver device; and
a detection circuit configured to monitor a voltage value of the conductor and a time for the voltage value to reach a pre-determined threshold value in response to the reference current and detect a presence of the externally coupled receiver device based on the monitored time, wherein the voltage value rises slower when the externally coupled receiver device is connected and enabled to receive the communication signal than when the externally coupled receiver device is not connected or is not enabled to receive the communication signal.
10. The device of claim 9 , wherein the reference current is led to a resistor and capacitor connected in series with a ground potential in the externally coupled receiver when the externally coupled receiver is enabled.
11. The device of claim 9 , wherein when the voltage value reaches the threshold value in a time greater than approximately 200 micro seconds.
12. The device of claim 9 , wherein the externally coupled receiver device is a peripheral device coupled through a serial bus with the detection circuit device.
13. The device of claim 12 , wherein the serial bus comprises two complementary data lines which are AC coupled in the externally coupled receiver device.
14. The device of claim 9 , wherein the shared buffer circuit is operable to split the reference current into a pair of reference currents and pass the pair of reference currents to the externally coupled receiver device.
15. The device of claim 9 , wherein the communication signal is a differential communication signal.
16. The device of claim 9 operable to interrupt power to the shared buffer circuit during the detect mode.
17. A universal serial bus USB hub device comprising:
a USB communication signal input; and
a detection circuit device operable to detect a presence of an externally coupled receiver device, the detection circuit device comprising:
a transmitter circuit operable to generate a reference current;
a shared buffer circuit configured to receive the reference current via a conductor, the shared buffer circuit also configured to selectively pass the reference current or a communication signal to the externally coupled receiver device, wherein the shared buffer circuit is further configured to switch between a detect mode where the reference current is provided to the externally coupled receiver device and between a communicate mode where the reference current is blocked and the communication signal is provided to the externally coupled receiver device; and
a detection circuit configured to monitor a voltage value of the conductor and a time for the voltage value to reach a pre-determined threshold value in response to the reference current and detect a presence of the externally coupled receiver device based on the monitored time, wherein the voltage value rises slower when the externally coupled receiver device is connected and enabled to receive the communication signal than when the externally coupled receiver device is not connected or is not enabled to receive the communication signal.
18. The device of claim 17 , wherein the reference current is led to a resistor and capacitor connected in series with a ground potential in the externally coupled receiver when the externally coupled receiver is enabled.
19. The device of claim 17 , wherein when the voltage value reaches the threshold value in a time greater than approximately 200 micro seconds.
20. The device of claim 17 , wherein the externally coupled receiver device is a peripheral device coupled through a serial bus with the hub device.
21. The device of claim 20 , wherein the serial bus comprises two complementary data lines which are AC coupled in the externally coupled receiver device.
22. The device of claim 17 , wherein the shared buffer circuit is operable to split the reference current into a pair of reference currents and pass the pair of reference currents to the externally coupled receiver device.
23. The device of claim 17 operable to interrupt power to the shared buffer circuit during the detect mode.