| AT Command | Purpose | Example | HC-12 Response | Notes |
|---|---|---|---|---|
| AT | Check comms | AT | OK | |
| AT+Bxxxx | Set Baud rate | AT+B9600 | OK+B9600 | The baud rate can be 1200bps, 2400bps, 4800bps, 9600bps, 19200bps, 38400bps, 57600bps, or 115200bps. The default is 9600bps. |
| AT+Cxxx | Set channel number | AT+C012 | OK+C012 | Channel numbers are from 001 to 127 although over 100 the performance can't be guaranteed. The working frequencies start at 433.4MHz and go in 400KHz steps thus channel 100 is at 473.0MHz. When a particular channel is used a gap of five channels should be left on adjacent systems to avoid interference and desensitization. |
| AT+FUx | Set transmission mode | AT+FU3 | OK+FU3 | |
| AT+Px | Set transmission power | AT+P3 | OK+P3 | Transmission power (x) can be set to 1 to 8 representing powers from -1dBm (0.8mW) to 20dBm (100mW) in 3dBm steps. The default setting is 8, 20dBm (100mW). |
| AT+Ry | Request a current setting | AT+RB | OK+B9600 | Request the currently set status of the module. AT+RY returns the baud rate, AT+RC returns the channel number, AT_RF returns the transmission mode, and AT+RP return the transmission power. |
| AT+RX | Request all current settings | AT+RX | OK+FU3 OK+B9600 OK+C001 OK+RP:+20dBm | All the current settings are returned togther |
| AT+Udps | Set data format | AT+U801 | OK+U801 | This sets the number of data bits (d), the parity (N = none, O = odd, and E = even), and stop bits (1 = one stop bit, 2 = two stop bits, and 3 = 1.5 stop bits). |
| AT+V | Request the module's current firmware version | AT+V | OK+HC-12_v2.3 | |
| AT+SLEEP | Enter sleep mode | AT+SLEEP | OK+SLEEP | Enter sleep mode on exiting command mode. Power cycling wakes the module up again |
| AT+DEFAULT | Sets default values for all parameters | AT+DEFAULT | OK_DEFAULT | This sets the module to 9600bps, 8 data bits, no parity, 1 stop bit, channel 001, and transmission mode FU3. |
| AT+UPDATE | Prepare for new firmware | Puts the module into update mode waiting for new firmware. Power cycle to return to normal operation. |
All commands must be sent at 9600bps, 8n1 mode regardless of any transmission settings.