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Adding 10-bit i2c addressing support to the SDK #721

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zbaltzer228 wants to merge 2 commits from zbaltzer228/develop into develop

zbaltzer228 commented

2022-01-30 15:42:02 -06:00

(Migrated from github.com)

Fixes #720

Raspberry Pi Pico SDK with 10-bit i2c addressing support

As of v1.3.0 of the SDK, neither 10-bit i2c master mode nor 10-bit i2c slave mode is implemented.

The RP2040 Datasheet
suggests, in two places that I can find, that 10-bit i2c addressing is not supported in slave mode.


Figure 1 - Suggesting 10-bit addressing is only available in Master mode


Figure 2 - Also suggesting 10-bit addressing is only available in Master mode

Introducing 10-bit i2c addressing support

In the revised i2c.h
there are 10 new functions

i2c_init_10bit
i2c_set_slave_mode_10bit
i2c_write_blocking_until_10bit
i2c_read_blocking_until_10bit
i2c_write_timeout_us_10bit
i2c_write_timeout_per_char_us_10bit
i2c_read_timeout_us_10bit
i2c_read_timeout_per_char_us_10bit
i2c_write_blocking_10bit
i2c_read_blocking_10bit

In the revised i2c.c
there are 3 new functions

i2c_reserved_addr_10bit
i2c_write_blocking_internal_10bit
i2c_read_blocking_internal_10bit

All prototypes are identical to their non-10-bit-qualified counterparts,
except wherever there is a uint8_t addr parameter, it has been replaced with
uint16_t addr.

Their functionality is also identical, but adapted to 10-bit addressing.

Example usage is found at RP2040_10bit_i2c_host.c
and RP2040_10bit_i2c_periph.c

Overview of a 10-bit i2c transaction using the examples

RP2040_10bit_i2c_host and RP2040_10bit_i2c_periph were built using the modified SDK proposed here.

Due to the limitations of the scope used to measure the i2c bus, the transaction
will be split across 6 different pictures.

In whole, the i2c host writes 2 bytes to the bus for address 0x02CF, then asks
the device with address 0x02CF for 3 bytes in response.


Figure 3 - Start of the i2c host write

The host initiates a transaction by dropping SDA while SCL is held high.

The next 5 bits are a specific sequence, 0b11110, reserved by the i2c spec to signal a 10-bit transaction,
followed by the 2 most significant bits of the 10-bit address, in this case 0x2.

The next byte delivers the rest of the 10-bit address, 0xCF.


Figure 4 - End of the i2c host write

Here, the 2 bytes are written to the bus, 0xA5 proceeded by 0x5A with the required ACK inbetween.


Figure 5 - Start of the i2c host read request

The host then starts a read request by transmitting the peripheral address, 0x02CF in a similar manner to Figure 3.
The R/W bit suggests a write, even though this is a read request. This is solved by
transmitting a 3rd byte with the Read bit set.


Figure 6 - Start of the i2c host read request

The host transmits its 3rd and final byte for the read request, this is a repeat of the first
start byte, with the reserved 0b11110 and 2 most significant bits of the periph address,
but with the Read bit set.

The peripheral then holds SDA low while it prepares to transmit its data.


Figure 7 - Start of the i2c periph write

The periph transmits its data and gets the required ACK, it transmits 3 bytes in total.
The first being a constant 0x5A, and the last two bytes are a counter that is incremented
each time a i2c transaction takes place.


Figure 8 - End of the i2c transaction

At the end, the host has acknowledged the bytes its expects and stops driving SCL.

In conclusion

The RP2040 does, in fact, support 10-bit addressing in both host and peripheral modes.
The changes required to the SDK to fully support 10-bit addressing are provided in i2c.h
and i2c.c

Fixes #720 # Raspberry Pi Pico SDK with 10-bit i2c addressing support As of v1.3.0 of the SDK, neither 10-bit i2c master mode nor 10-bit i2c slave mode is implemented. The [RP2040 Datasheet](https://datasheets.raspberrypi.com/rp2040/rp2040-datasheet.pdf) suggests, in two places that I can find, that 10-bit i2c addressing is not supported in slave mode. | ![](https://raw.githubusercontent.com/zbaltzer228/pico-sdk-i2c-10bit-explained/develop/Support/10biti2cEvidence1.jpg) | |:--:| | Figure 1 - Suggesting 10-bit addressing is only available in Master mode| | ![](https://raw.githubusercontent.com/zbaltzer228/pico-sdk-i2c-10bit-explained/develop/Support/10biti2cEvidence2.jpg) | |:--:| | Figure 2 - Also suggesting 10-bit addressing is only available in Master mode | ## Introducing 10-bit i2c addressing support In the revised [i2c.h](https://github.com/zbaltzer228/pico-sdk-i2c-10bit-explained/blob/develop/src/rp2_common/hardware_i2c/include/hardware/i2c.h) there are 10 new functions - i2c_init_10bit - i2c_set_slave_mode_10bit - i2c_write_blocking_until_10bit - i2c_read_blocking_until_10bit - i2c_write_timeout_us_10bit - i2c_write_timeout_per_char_us_10bit - i2c_read_timeout_us_10bit - i2c_read_timeout_per_char_us_10bit - i2c_write_blocking_10bit - i2c_read_blocking_10bit In the revised [i2c.c](https://github.com/zbaltzer228/pico-sdk-i2c-10bit-explained/blob/develop/src/rp2_common/hardware_i2c/i2c.c) there are 3 new functions - i2c_reserved_addr_10bit - i2c_write_blocking_internal_10bit - i2c_read_blocking_internal_10bit All prototypes are identical to their non-10-bit-qualified counterparts, except wherever there is a **uint8_t addr** parameter, it has been replaced with **uint16_t addr**. Their functionality is also identical, but adapted to 10-bit addressing. Example usage is found at [RP2040_10bit_i2c_host.c](https://github.com/zbaltzer228/pico-sdk-i2c-10bit-explained/blob/develop/Examples/RP2040_10bit_i2c_host/RP2040_10bit_i2c_host.c) and [RP2040_10bit_i2c_periph.c](https://github.com/zbaltzer228/pico-sdk-i2c-10bit-explained/blob/develop/Examples/RP2040_10bit_i2c_periph/RP2040_10bit_i2c_periph.c) ### Overview of a 10-bit i2c transaction using the examples RP2040_10bit_i2c_host and RP2040_10bit_i2c_periph were built using the modified SDK proposed here. Due to the limitations of the scope used to measure the i2c bus, the transaction will be split across 6 different pictures. In whole, the i2c host writes 2 bytes to the bus for address 0x02CF, then asks the device with address 0x02CF for 3 bytes in response. | ![](https://raw.githubusercontent.com/zbaltzer228/pico-sdk-i2c-10bit-explained/develop/Support/StartOfHostI2CWriteLabeled.jpg) | |:--:| | Figure 3 - Start of the i2c host write | The host initiates a transaction by dropping SDA while SCL is held high. The next 5 bits are a specific sequence, 0b11110, reserved by the i2c spec to signal a 10-bit transaction, followed by the 2 most significant bits of the 10-bit address, in this case 0x2. The next byte delivers the rest of the 10-bit address, 0xCF. | ![](https://raw.githubusercontent.com/zbaltzer228/pico-sdk-i2c-10bit-explained/develop/Support/EndOfHostI2CWriteLabeled.jpg) | |:--:| | Figure 4 - End of the i2c host write | Here, the 2 bytes are written to the bus, 0xA5 proceeded by 0x5A with the required ACK inbetween. | ![](https://raw.githubusercontent.com/zbaltzer228/pico-sdk-i2c-10bit-explained/develop/Support/StartOfHostI2CReqLabeled.jpg) | |:--:| | Figure 5 - Start of the i2c host read request | The host then starts a read request by transmitting the peripheral address, 0x02CF in a similar manner to Figure 3. The R/W bit suggests a write, even though this is a read request. This is solved by transmitting a 3rd byte with the Read bit set. | ![](https://raw.githubusercontent.com/zbaltzer228/pico-sdk-i2c-10bit-explained/develop/Support/EndOfHostI2CReqLabeled.jpg) | |:--:| | Figure 6 - Start of the i2c host read request | The host transmits its 3rd and final byte for the read request, this is a repeat of the first start byte, with the reserved 0b11110 and 2 most significant bits of the periph address, but with the Read bit set. The peripheral then holds SDA low while it prepares to transmit its data. | ![](https://raw.githubusercontent.com/zbaltzer228/pico-sdk-i2c-10bit-explained/develop/Support/StartOfPeriphI2CWrite.jpg) | |:--:| | Figure 7 - Start of the i2c periph write | The periph transmits its data and gets the required ACK, it transmits 3 bytes in total. The first being a constant 0x5A, and the last two bytes are a counter that is incremented each time a i2c transaction takes place. | ![](https://raw.githubusercontent.com/zbaltzer228/pico-sdk-i2c-10bit-explained/develop/Support/EndOfPeriphI2CWriteLabeled.jpg) | |:--:| | Figure 8 - End of the i2c transaction | At the end, the host has acknowledged the bytes its expects and stops driving SCL. ## In conclusion The RP2040 does, in fact, support 10-bit addressing in both host and peripheral modes. The changes required to the SDK to fully support 10-bit addressing are provided in [i2c.h](https://github.com/zbaltzer228/pico-sdk/blob/develop/src/rp2_common/hardware_i2c/include/hardware/i2c.h) and [i2c.c](https://github.com/zbaltzer228/pico-sdk/blob/develop/src/rp2_common/hardware_i2c/i2c.c)

lurch (Migrated from github.com) reviewed

2023-01-19 10:49:16 -06:00

src/rp2_common/hardware_i2c/i2c.c

addr here is a uint8_t, so it's impossible for it to be >= 0x400 ? (i.e. is this a typo?)

`addr` here is a `uint8_t`, so it's impossible for it to be `>= 0x400` ? (i.e. is this a typo?)

zbaltzer228 (Migrated from github.com) reviewed

2023-01-19 11:04:15 -06:00

src/rp2_common/hardware_i2c/i2c.c

You are absolutely correct - it should be uint16_t, not uint8_t on line 144.

nonchip (Migrated from github.com) reviewed

2023-09-08 05:08:32 -05:00

src/rp2_common/hardware_i2c/i2c.c

@zbaltzer228 are you gonna fix that so we can get your feature, oooor...?

JolonB (Migrated from github.com) reviewed

2025-01-28 02:19:34 -06:00

src/rp2_common/hardware_i2c/i2c.c

It'd be great if this could be merged, but it's worth pointing out that this line should not be uint16_t, as this is the 7-bit addressing function. This should stay as 0x80. However, I believe the invalid_params_if in the 10-bit function should be 0x400 instead.

It'd be great if this could be merged, but it's worth pointing out that this line should not be uint16_t, as this is the 7-bit addressing function. This should stay as 0x80. However, I believe the `invalid_params_if` in the 10-bit function should be 0x400 instead.

lurch (Migrated from github.com) reviewed

2025-01-28 07:06:40 -06:00

src/rp2_common/hardware_i2c/i2c.c

This PR is now so old that it has merge-conflicts which need to be resolved.

This pull request has changes conflicting with the target branch.

src/rp2_common/hardware_i2c/i2c.c
src/rp2_common/hardware_i2c/include/hardware/i2c.h

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Merge pull request 'Adding 10-bit i2c addressing support to the SDK' (#721) from zbaltzer228/develop into develop

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Reviewed-on: https://git.richey.dev/gh-raspberrypi/pico-sdk/pulls/721

Merge pull request 'Adding 10-bit i2c addressing support to the SDK' (#721) from zbaltzer228/develop into develop

Reviewed-on: https://git.richey.dev/gh-raspberrypi/pico-sdk/pulls/721

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