Using Software Interrupts

The Apollo3 module has many hardware peripherals capable of generating software interrupts. In order to use these, a special function naming system is used to call the various ISRs (Interrupt Service Routines).

Software Interrupts

For more information on how and when each peripheral-specific interrupt is called, have a look at the Apollo3 datasheet and the examples in the Ambiq SDK.

Note: this does not include hardware interrupts. To use those, look at the interrupts example here and the official Arduino reference here.

The Apollo3 microcontroller's interrupts are mapped through the NVIC (Nested Vectored Interrupt Controller). See section 3.1 of the datasheet for more details. The following is a table of the specific peripheral interrupt, its IRQ number, and its ISR name.

Peripheral Name	IRQ Number	ISR Name
Brownout	0	am_brownout_isr
Watchdog	1	am_watchdog_isr
RTC	2	am_rtc_isr
Voltage Comparator	3	am_vcomp_isr
I2C/SPI Slave	4	am_ioslave_ios_isr
I2C/SPI Slave Register Address	5	am_ioslave_acc_isr
I2C/SPI Master 0	6	am_iomaster0_isr
I2C/SPI Master 1	7	am_iomaster1_isr
I2C/SPI Master 2	8	am_iomaster2_isr
I2C/SPI Master 3	9	am_iomaster3_isr
I2C/SPI Master 4	10	am_iomaster4_isr
I2C/SPI Master 5	11	am_iomaster5_isr
BLE	12	am_ble_isr
GPIO	13	am_gpio_isr
Counter/Timers	14	am_ctimer_isr
UART0	15	am_uart_isr
UART1	16	am_uart1_isr
SCARD	17	am_scard_isr
ADC	18	am_adc_isr
PDM	19	am_pdm_isr
MSPI	20	am_mspi_isr
Stimer Capture/Overflow	22	am_stimer_isr
Stimer Compare 0	23	am_stimer_cmpr0_isr
Stimer Compare 1	24	am_stimer_cmpr1_isr
Stimer Compare 2	25	am_stimer_cmpr2_isr
Stimer Compare 3	26	am_stimer_cmpr3_isr
Stimer Compare 4	27	am_stimer_cmpr4_isr
Stimer Compare 5	28	am_stimer_cmpr5_isr
Stimer Compare 6	29	am_stimer_cmpr6_isr
Stimer Compare 7	30	am_stimer_cmpr7_isr
Clock Control	31	am_clkgen_isr

Using Interrupts

To use any of the ISRs listed, make sure to prefix the function with extern "C" before the function declaration. For example:

extern "C" void am_pdm0_isr(void) {
    ...
}

Note: all variables used within an ISR should also be declared with the volatile keyword.

The names of all of the ISRs can be found in the startup_gcc.c files for each variant of Apollo3 board.