Example Explanation of the AT Command Serial Port Section for the KT1025A BT301 Bluetooth Audio Chip FM Radio Version

 

1. Chip Power-On Initialization

1. Upon powering on, the chip actively returns some information, but this does not include FM-related information. FM-related information will only be returned after sending a command to switch to FM mode.

2. The chip supports automatic station search, which scans the range of 87.5 MHz to 108.0 MHz to find available stations or those with good signal strength, then automatically stores them.

3. Important FM information includes three items (these exist to facilitate user display purposes):

(1) Current frequency point, i.e., a frequency between 87.5 MHz and 108.0 MHz, with a step of 0.1 MHz.

(2) Current station.

(3) Total number of stored stations.

2. Control Commands Related to the Chips FM Section

(1) After the chip enters FM mode, the user needs to send commands to trigger corresponding actions, such as automatic station search, previous station, next station, increase frequency by one step, decrease frequency by one step, etc. These are control commands.

(2) The chip automatically handles station storage and other information, so the user does not need to manage this.

AT+FC00  Start automatic station search; sending it again stops the search.

AT+FC04  Automatically search for stations downward (lower frequencies).

AT+FC01  Reserved.

AT+FC05  Automatically search for stations upward (higher frequencies).

AT+FC02  Switch to the previous station.

AT+FC06  Decrease frequency by one step (previous frequency point).

AT+FC03  Switch to the next station.

AT+FC07  Increase frequency by one step (next frequency point).

AT+FF0875  Specify FM to jump to 87.5 MHz.

AT+FF1080  Specify FM to jump to 108.0 MHz.

Query Commands Related to the Chips FM Section:

AT+PF  Query the chip's current frequency point — the chip will return PF+0875 (e.g., 87.5 MHz).

AT+PC  Query the station number at the current frequency point — the chip will return PC+0001 (e.g., Station 1).

AT+PT  Query the total number of stations found by the chip — the chip will return PT+0012 (e.g., 12 stations).

3. Button Operation Instructions for Testing the BT301 Demo Board

For the Button Functions of FM:

1. Long-pressing the PP key initiates automatic station search. The indicator light will flash quickly, pausing briefly when a station is found, playing it for 1 second, then continuing to search for the next station.

2. FM operates in the default frequency range of 87.5 MHz to 108.0 MHz.

3. After the automatic station search is complete, you can use “Previous track” (PREV) or “Next track” (NEXT) to switch between stations.

4. Instructions for Serial Port Debugging and Testing

1. As shown in the left image above, this is the information actively returned after sending a command via the serial port to switch to FM mode:

(1) PF+0886 = Indicates the current frequency is 88.6 MHz.

(2) PC+0000 = Indicates that this frequency is not a valid station, so no station is locked.

(3) PT+0012 = Indicates the chip previously performed an automatic station search and stored 12 valid stations, i.e., 0x0C (hexadecimal for 12).

2. As shown in the right image above, this is after sending the automatic station search command via the serial port; the chip starts the automatic search and returns real-time information:

(1) Refer to the corresponding commands for specifics.

(2) To explain, the two arrows indicate: one for a station found during the search, and the other for the completion of the search.

=> For detailed debugging, use a serial debugging tool on the computer to observe the output.