45 lines
1.8 KiB
ReStructuredText
45 lines
1.8 KiB
ReStructuredText
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Accessing peripherals directly via registers
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============================================
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The ESP32's peripherals can be controlled via direct register reads and writes.
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This requires reading the datasheet to know what registers to use and what
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values to write to them. The following example shows how to turn on and change
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the prescaler of the MCPWM0 peripheral.
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.. code-block:: python3
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from micropython import const
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from machine import mem32
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# Define the register addresses that will be used.
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DR_REG_DPORT_BASE = const(0x3FF00000)
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DPORT_PERIP_CLK_EN_REG = const(DR_REG_DPORT_BASE + 0x0C0)
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DPORT_PERIP_RST_EN_REG = const(DR_REG_DPORT_BASE + 0x0C4)
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DPORT_PWM0_CLK_EN = const(1 << 17)
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MCPWM0 = const(0x3FF5E000)
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MCPWM1 = const(0x3FF6C000)
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# Enable CLK and disable RST.
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print(hex(mem32[DPORT_PERIP_CLK_EN_REG] & 0xffffffff))
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print(hex(mem32[DPORT_PERIP_RST_EN_REG] & 0xffffffff))
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mem32[DPORT_PERIP_CLK_EN_REG] |= DPORT_PWM0_CLK_EN
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mem32[DPORT_PERIP_RST_EN_REG] &= ~DPORT_PWM0_CLK_EN
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print(hex(mem32[DPORT_PERIP_CLK_EN_REG] & 0xffffffff))
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print(hex(mem32[DPORT_PERIP_RST_EN_REG] & 0xffffffff))
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# Change the MCPWM0 prescaler.
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print(hex(mem32[MCPWM0])) # read PWM_CLK_CFG_REG (reset value = 0)
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mem32[MCPWM0] = 0x55 # change PWM_CLK_PRESCALE
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print(hex(mem32[MCPWM0])) # read PWM_CLK_CFG_REG
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Note that before a peripheral can be used its clock must be enabled and it must
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be taken out of reset. In the above example the following registers are used
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for this:
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- ``DPORT_PERI_CLK_EN_REG``: used to enable a peripheral clock
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- ``DPORT_PERI_RST_EN_REG``: used to reset (or take out of reset) a peripheral
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The MCPWM0 peripheral is in bit position 17 of the above two registers, hence
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the value of ``DPORT_PWM0_CLK_EN``.
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