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| en:multiasm:paarm:chapter_5_9 [2026/05/27 09:49] – [Peripheral Management in RPi] ktokarz | en:multiasm:paarm:chapter_5_9 [2026/05/27 09:51] (current) – [Pulse Width Modulation] ktokarz |
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| Basically, with a single GPIO line, you can do a lot: control almost any hardware, read or take measurements, generate wireless signals, and more. Of course, it is easier to control hardware designed for specific purposes, such as I2C communication in the previously described examples. As with the bit-banging technique, it is possible to generate periodic digital signals and control their duty cycle. | Basically, with a single GPIO line, you can do a lot: control almost any hardware, read or take measurements, generate wireless signals, and more. Of course, it is easier to control hardware designed for specific purposes, such as I2C communication in the previously described examples. As with the bit-banging technique, it is possible to generate periodic digital signals and control their duty cycle. |
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| In Raspberry Pi 5, the RP1 chip documentation contains much more information on pulse-width modulation than on basic communication interfaces. PWM registers are on the internal peripheral bus; the base addresses for PWM0 and PWM1 are ''0x40098000'' and ''0x4009C000'', respectively. This hardware is located in the RP1 chip and accessed through PCIe. The Linux OS sets up hardware address mapping, and this mapping is not exposed as a simple fixed physical address that can be accessed with just ''<fc #800000>LDR</fc>''/''<fc #800000>STR</fc>'' instructions from user space. To access the PWM registers, it is necessary to execute the code at least at the EL1 level and to know already the PCIe mapping, or the mapping can be implemented manually. Again, this is too advanced and carries a risk of breaking something. | In Raspberry Pi 5, the RP1 chip documentation contains much more information on pulse-width modulation than on basic communication interfaces. PWM registers are on the internal peripheral bus; the base addresses for PWM0 and PWM1 are ''0x40098000'' and ''0x4009C000'', respectively. This hardware is located in the RP1 chip and accessed through PCIe. Linux sets up hardware address mapping, and this mapping is not exposed as a simple fixed physical address that can be accessed with just ''<fc #800000>LDR</fc>''/''<fc #800000>STR</fc>'' instructions from user space. To access the PWM registers, it is necessary to execute the code at least at the EL1 level and to know already the PCIe mapping, or the mapping can be implemented manually. Again, this is too advanced and carries a risk of breaking something. |
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| Before proceeding, the base addresses must be checked at least three times (**NO JOKES**) and, if needed, replaced. The PWM0_BASE and IO_BANK0_BASE addresses are already mapped and known for the Raspberry Pi 5. In the example, the GPIO line 18 will be used. | Before proceeding, the base addresses must be checked at least three times (**NO JOKES**) and, if needed, replaced. The PWM0_BASE and IO_BANK0_BASE addresses are already mapped and known for the Raspberry Pi 5. In the example, the GPIO line 18 will be used. |
