smi(3)

💖 smi(3) — SMI bus support 💖

okay bestie, gather round, because we're talking about the smi page from the Library Functions Manual and it's literally all about letting you touch the SMI bus 🦋 no cap.

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✨ NAME ✨

smi — SMI bus support

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🌸 SYNOPSIS 🌸

Functions

int bcm2835_smi_begin (void)
void bcm2835_smi_end (void)
void bcm2835_smi_set_timing (uint32_t smichannel, uint32_t readchannel,
    uint32_t setupcycles, uint32_t strobecycles, uint32_t holdcycles,
    uint32_t pacecycles)
void bcm2835_smi_write (uint32_t smichannel, uint8_t data, uint32_t
    address)
uint32_t bcm2835_smi_read (uint32_t smichannel, uint32_t address)

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🎀 Detailed Description 🎀

Allows access to SMI bus. that's it, that's the whole vibe. short. iconic. 💅

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👑 Function Documentation 👑

🫶 int bcm2835_smi_begin (void) [extern]

Start SMI operations. this one forces the RPi SMI pins P1-19 (MOSI), P1-21 (MISO), P1-23 (CLK), P1-24 (CE0) and P1-26 (CE1) into alternate function ALT1, which is what enables those pins for the SMI interface. slay. ✨

bestie you should call bcm2835_smi_end() when all your SMI functions are complete, so the pins go back to their default functions. don't leave them hanging fr fr 😭

also, heads up: only address bits SA0 to SA3 are available as RPi uses GPIO0 (SA5) and GPIO1 (SA4) for I2C HAT identification EEPROM access. iykyk.

See also

• bcm2835_smi_end()

Returns

• 1 if successful, 0 otherwise (perhaps because you are not running as root) 💀

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🌈 void bcm2835_smi_end (void) [extern]

End SMI operations. the SMI pins P1-19 (MOSI), P1-21 (MISO), P1-23 (CLK), P1-24 (CE0) and P1-26 (CE1) are returned to their default INPUT behaviour. clean exit, main character energy 👑

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⭐ uint32_t bcm2835_smi_read (uint32_t smichannel, uint32_t address) [extern]

Reads one byte from SMI bus. uses polled transfer as described in BCM 2835 ARM Peripherals manual 📖

Parameters

• smichannel — SMI configuration slot to use (0 to 3)
• address — The address to read from

Returns

• value read from SMI bus 💖

See also

• bcm2835_smi_readnb()

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🧚 void bcm2835_smi_set_timing (uint32_t smichannel, uint32_t readchannel, uint32_t setupcycles, uint32_t strobecycles, uint32_t holdcycles, uint32_t pacecycles) [extern]

Setup SMI bus cycle timing parameters. okay so there are four SMI channels for read operation and four channels for write operation. cycles are expressed as multiple of 8ns ⏱️

not me having to say this: Pace cycles are not used (no effect on hardware) but they are required for configuration. it is recommended to set this value to 1 (and not 0) to have the smallest cycle in case the hardware would recognize it. so like… set it, bestie 🙈

Parameters

• smichannel — SMI configuration slot to setup (0 to 3)
• readchannel — Set to 1 to configure the read channel (0 = configure write channel)
• setupcycles — Time between address assertion on bus and OE/WR signal assertion
• strobecycles — Duration of OE/WR signal assertion
• holdcycles — Time after OE/WR deassertion before address is deasserted
• pacecycles — Time before next SMI bus cycle

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💜 void bcm2835_smi_write (uint32_t smichannel, uint8_t data, uint32_t address) [extern]

Transfers one byte to SMI bus. uses polled transfer as described in BCM 2835 ARM Peripherals manual 🔥

Parameters

• timingslot — SMI configuration slot to use (0 to 3)
• data — The data byte to write
• address — The address to write to

See also

• bcm2835_smi_writenb()

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💌 Author 💌

Generated automatically by Doxygen for bcm2835 from the source code. it wrote itself, honestly, we're just here for the vibes 🎀

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and that's the whole page, bestie!! this beauty lives in bcm2835, Version 1.75 — so if you ever need to cite it, that's the version and that's the source, mwah 💋 periodt ✨