A detector for detecting the connection of an accessory including a microphone and/or the state of a switch associated with the microphone for a mobile device, wherein the detector comprises a first flag generator for time multiplexing the detection of a signal above a predetermined threshold for each of two comparators, such that for one time period one comparator output is detected and for a second time period the second comparator output is detected to thereby form a first flag; a second flag generator for determining the connection of microphone to thereby generate a second flag; a lookup table for determining the connection of the accessory and/or the state of the microphone switch from the first and second flags.
1. A headset detector comprises: A first flag generator configured to detect a connection of an accessory and to generate a first flag in response to the connection of the accessory, the accessory including a microphone and a switch connected to the microphone; a second flag generator including a low current source and a high current source, wherein the low current source is enabled during both a first time period and a second time period, the second flag generator configured to periodically detect a signal above a predetermined threshold for each of a first comparator and a second comparator, to enable the high current source only during the second time period, to set, in response to the first flag being generated during the first time period, a state of a second flag based on an output state of the first comparator, wherein the output of the first comparator is based on a current from the low current source during the first time period, and to set, in response to the first flag being generated during the second time period, the state of the second flag based on an output state of the second comparator, wherein the output of the second comparator is based on a current from the high current source during the second time period.
2. The detector of claim 1 , wherein the second flag generator includes:
a microphone device which has a variable current response;
wherein the first comparator is a high comparator having a first threshold, the second comparator is a low comparator having a second threshold, the current sources are switched on in a periodical manner and wherein the high current source is switched on for a fraction of the time of the low current source and wherein a current response of the microphone device is measured by the first comparator and the second comparator to generate the second flag.
3. The detector of claim 2 , wherein the switch is connected in parallel to the microphone device.
4. The detector of claim 2 , wherein the high comparator measures the current response when the high current source is on and the low comparator measures the current response when the low current source is on.
5. The detector of claim 4 , wherein the high current source is on for about 1/100 th of the time of the low current source is on.
6. The detector of claim 2 , further comprising a detection state machine for measuring outputs from both the high comparator and the low comparator to generate the second flag.
7. The detector of claim 2 , wherein the detection state machine controls the switching of the high current source and the low current source.
8. The detector of claim 2 , wherein the microphone device includes a JFET.
9. The detector of claim 2 , wherein determination of the connection of the microphone and/or the state of the switch associated with the microphone from the first and second flags is selected from the following:
no headsets;
headset without microphone;
headset with microphone;
headset with microphone, connected in serial with a closed switch;
headset with microphone, connected in serial with an open switch;
headset with microphone, connected in parallel with a closed switch; and
headset with microphone, connected in parallel with an open switch.
10. A mobile device including the detector of claim 1 .
11. The mobile device of claim 10 , in the form of a mobile telephone.
12. A headset including a microphone for use with the mobile device according to claim 10 .
13. A headset according to claim 12 including a parallel switch.
14. A method of headset detection comprising the steps of: generating a current from a low current source during both a first time period and a second time period; generating a current from a high current source only during the second time period; determining a connection of an accessory including a microphone and a switch connected to the microphone; generating a first flag in response to the connection; determining a second flag by periodically detecting a signal above a predetermined threshold for each of a first comparator and a second comparator; setting, in response to the first flag being generated during the first time period, a state of the second flag based on an output state of the first comparator, wherein the output of the first comparator is based on a current from the low current source during the first time period; setting, in response to the first flag being generated during the second time period, the state of the second flag based on an output state of the second comparator, wherein the output of the second comparator is based on a current from the high current source during the second time period; and determining, by a lookup table, during the first and second time periods, at least one of a group consisting of the connection of the microphone and a state of the switch associated with the microphone from the states of the first and second flags.
15. The method of claim 14 , further comprising the step of connecting the switch in parallel with the microphone device.
16. The method of claim 14 , further comprising controlling the switching of the current source and the second current source in a periodical time varying manner.
17. The method of claim 16 , further comprising switching on the first comparator for about 1/100 th of the time of the second comparator.
18. A non-transitory computer program comprising instructions for carrying out operations of headset detection, the operations comprising: generating a current from a low current source during both a first time period and a second time period; generating a current from a high current source only during the second time period; determining a connection of an accessory including a microphone and a switch connected to the microphone; generating a first flag in response to the connection; determining a second flag by periodically detecting a signal above a predetermined threshold for each of a first comparator and a second comparator; setting, in response to the first flag being generated during the first time period, a state of the second flag based on an output state of the first comparator, wherein the output of the first comparator is based on a current from the low current source during the first time period; setting, in response to the first flag being generated during the second time period, the state of the second flag based on an output state of the second comparator, wherein the output of the second comparator is based on a current from the high current source during the second time period; and determining, by a lookup table, during the first and second time periods, the at least one of a group consisting of the connection of the microphone and a state of the switch associated with the microphone from the states of the first and second flags.
19. The detector of claim 3 , wherein the high comparator measures the current response when the high current source is on and the low comparator measures the current response when the low current source is on.
20. The method of claim 14 , further comprising:
determining that the state of the switch is a closed switch connected in parallel with the microphone; and
continuously generating the current from the high current source as the second time period until the state of the switch is an opened switch or the accessory is removed.