Accessing peripherals directly via registers ============================================ The ESP32's peripherals can be controlled via direct register reads and writes. This requires reading the datasheet to know what registers to use and what values to write to them. The following example shows how to turn on and change the prescaler of the MCPWM0 peripheral. .. code-block:: python3 from micropython import const from machine import mem32 # Define the register addresses that will be used. DR_REG_DPORT_BASE = const(0x3FF00000) DPORT_PERIP_CLK_EN_REG = const(DR_REG_DPORT_BASE + 0x0C0) DPORT_PERIP_RST_EN_REG = const(DR_REG_DPORT_BASE + 0x0C4) DPORT_PWM0_CLK_EN = const(1 << 17) MCPWM0 = const(0x3FF5E000) # Enable CLK and disable RST. print(hex(mem32[DPORT_PERIP_CLK_EN_REG] & 0xffffffff)) print(hex(mem32[DPORT_PERIP_RST_EN_REG] & 0xffffffff)) mem32[DPORT_PERIP_CLK_EN_REG] |= DPORT_PWM0_CLK_EN mem32[DPORT_PERIP_RST_EN_REG] &= ~DPORT_PWM0_CLK_EN print(hex(mem32[DPORT_PERIP_CLK_EN_REG] & 0xffffffff)) print(hex(mem32[DPORT_PERIP_RST_EN_REG] & 0xffffffff)) # Change the MCPWM0 prescaler. print(hex(mem32[MCPWM0])) # read PWM_CLK_CFG_REG (reset value = 0) mem32[MCPWM0] = 0x55 # change PWM_CLK_PRESCALE print(hex(mem32[MCPWM0])) # read PWM_CLK_CFG_REG The specific addresses will be different on different ESP32 models. For example, ESP32-S3 uses these values: .. code-block:: python3 DR_REG_DPORT_BASE = const(0x600C_0000) DPORT_PERIP_CLK_EN0_REG = const(DR_REG_DPORT_BASE + 0x0018) DPORT_PERIP_RST_EN0_REG = const(DR_REG_DPORT_BASE + 0x0020) DPORT_PWM0_CLK_EN = const(1 << 17) MCPWM0 = const(0x6001_E000 + 0x0004) ... Note that before a peripheral can be used its clock must be enabled and it must be taken out of reset. In the above example the following registers are used for this: - ``DPORT_PERI_CLK_EN_REG``: used to enable a peripheral clock - ``DPORT_PERI_RST_EN_REG``: used to reset (or take out of reset) a peripheral The MCPWM0 peripheral is in bit position 17 of the above two registers, hence the value of ``DPORT_PWM0_CLK_EN``. Synchronous access to pins directly via registers ------------------------------------------------- The following code shows how to access pins directly via registers. It has been tested on a generic ESP32 board. It configures pins 16, 17, 32 and 33 in output mode via registers, and switches pin output values via registers. Pins 16 and 17 are switched simultaneously. .. code-block:: python3 from micropython import const from machine import mem32, Pin GPIO_OUT_REG = const(0x3FF44004) # GPIO 0-31 output register GPIO_OUT1_REG = const(0x3FF44010) # GPIO 32-39 output register GPIO_ENABLE_REG = const(0x3FF44020) # GPIO 0-31 output enable register GPIO_ENABLE1_REG = const(0x3FF4402C) # GPIO 32-39 output enable register M16 = 1 << 16 # Pin(16) bit mask M17 = 1 << 17 # Pin(17) bit mask M32 = 1 << (32-32) # Pin(32) bit mask M33 = 1 << (33-32) # Pin(33) bit mask # Enable pin output mode like # p16 = Pin(16, mode=Pin.OUT) # p17 = Pin(17, mode=Pin.OUT) # p32 = Pin(32, mode=Pin.OUT) # p33 = Pin(33, mode=Pin.OUT) mem32[GPIO_ENABLE_REG] = mem32[GPIO_ENABLE_REG] | M16 | M17 mem32[GPIO_ENABLE1_REG] = mem32[GPIO_ENABLE1_REG] | M32 | M33 print(hex(mem32[GPIO_OUT_REG]), hex(mem32[GPIO_OUT1_REG])) # Set outputs to 1 like # p16(1) # p17(1) # p32(1) # p33(1) mem32[GPIO_OUT_REG] = mem32[GPIO_OUT_REG] | M16 | M17 mem32[GPIO_OUT1_REG] = mem32[GPIO_OUT1_REG] | M32 | M33 print(hex(mem32[GPIO_OUT_REG]), hex(mem32[GPIO_OUT1_REG])) # Set outputs to 0 like # p16(0) # p17(0) # p32(0) # p33(0) mem32[GPIO_OUT_REG] = mem32[GPIO_OUT_REG] & ~(M16 | M17) mem32[GPIO_OUT1_REG] = mem32[GPIO_OUT1_REG] & ~(M32 | M33) print(hex(mem32[GPIO_OUT_REG]), hex(mem32[GPIO_OUT1_REG])) while True: # Set outputs to 1 mem32[GPIO_OUT_REG] = mem32[GPIO_OUT_REG] | M16 | M17 mem32[GPIO_OUT1_REG] = mem32[GPIO_OUT1_REG] | M32 | M33 # Set outputs to 0 mem32[GPIO_OUT_REG] = mem32[GPIO_OUT_REG] & ~(M16 | M17) mem32[GPIO_OUT1_REG] = mem32[GPIO_OUT1_REG] & ~(M32 | M33) Output is:: 0x0 0x0 0x30000 0x3 0x0 0x0 Pins 16 and 17 are switched synchronously: .. image:: img/mem32_gpio_output.jpg Same image on pins 32 and 33. Note that pins 34-36 and 39 are inputs only. Also pins 1 and 3 are Tx, Rx of the REPL UART, pins 6-11 are connected to the built-in SPI flash.