# Programming ULP FSM Coprocessor Using C Macros (Legacy)

In addition to the existing binutils port for the ESP32 ULP coprocessor, it is possible to generate programs for the ULP FSM coprocessor by embedding assembly-like macros into an ESP32 application. Here is an example how this can be done:

    const ulp_insn_t program[] = {
        I_MOVI(R3, 16),         // R3 <- 16
        I_LD(R0, R3, 0),        // R0 <- RTC_SLOW_MEM[R3 + 0]
        I_LD(R1, R3, 1),        // R1 <- RTC_SLOW_MEM[R3 + 1]
        I_ADDR(R2, R0, R1),     // R2 <- R0 + R1
        I_ST(R2, R3, 2),        // R2 -> RTC_SLOW_MEM[R2 + 2]
        I_HALT()
    };
    size_t load_addr = 0;
    size_t size = sizeof(program)/sizeof(ulp_insn_t);
    ulp_process_macros_and_load(load_addr, program, &size);
    ulp_run(load_addr);

The `program` array is an array of `ulp_insn_t`, i.e., ULP coprocessor instructions. Each `I_XXX` preprocessor define translates into a single 32-bit instruction. Arguments of these preprocessor defines can be register numbers (`R0 — R3`) and literal constants. See the API reference section at the end of this guide for descriptions of instructions and arguments they take.

Note

Because some of the instruction macros expand to inline function calls, defining such array in global scope will cause the compiler to produce an "initializer element is not constant" error. To fix this error, move the definition of instructions array into local scope.

Note

Load, store and move instructions use addresses expressed in 32-bit words. Address 0 corresponds to the first word of `RTC_SLOW_MEM`. This is different to how address arguments are handled in assembly code of the same instructions. See the section Note About Addressing for more details for reference.

To generate branch instructions, special `M_` preprocessor defines are used. `M_LABEL` define can be used to define a branch target. Label identifier is a 16-bit integer. `M_Bxxx` defines can be used to generate branch instructions with target set to a particular label.

Implementation note: these `M_` preprocessor defines will be translated into two ulp_insn_t values: one is a token value which contains label number, and the other is the actual instruction. `ulp_process_macros_and_load` function resolves the label number to the address, modifies the branch instruction to use the correct address, and removes the extra `ulp_insn_t` token which contains the label number.

Here is an example of using labels and branches:

    const ulp_insn_t program[] = {
        I_MOVI(R0, 34),         // R0 <- 34
        M_LABEL(1),             // label_1
        I_MOVI(R1, 32),         // R1 <- 32
        I_LD(R1, R1, 0),        // R1 <- RTC_SLOW_MEM[R1]
        I_MOVI(R2, 33),         // R2 <- 33
        I_LD(R2, R2, 0),        // R2 <- RTC_SLOW_MEM[R2]
        I_SUBR(R3, R1, R2),     // R3 <- R1 - R2
        I_ST(R3, R0, 0),        // R3 -> RTC_SLOW_MEM[R0 + 0]
        I_ADDI(R0, R0, 1),      // R0++
        M_BL(1, 64),            // if (R0 < 64) goto label_1
        I_HALT(),
    };
    RTC_SLOW_MEM[32] = 42;
    RTC_SLOW_MEM[33] = 18;
    size_t load_addr = 0;
    size_t size = sizeof(program)/sizeof(ulp_insn_t);
    ulp_process_macros_and_load(load_addr, program, &size);
    ulp_run(load_addr);

## API Reference

### Header File

- components/ulp/ulp_fsm/include/esp32/ulp.h

- This header file can be included with:

  >     #include "ulp.h"

- This header file is a part of the API provided by the `ulp` component. To declare that your component depends on `ulp`, add the following to your CMakeLists.txt:

  >     REQUIRES ulp

  > or

  >     PRIV_REQUIRES ulp

### Functions

static inline uint32_t SOC_REG_TO_ULP_PERIPH_SEL(uint32_t reg)

  Map SoC peripheral register to periph_sel field of RD_REG and WR_REG instructions.

  Parameters:

    reg -- peripheral register in RTC_CNTL_, RTC_IO_, SENS_, RTC_I2C peripherals.

  Returns:

    periph_sel value for the peripheral to which this register belongs.

### Unions

union ulp_insn
  #include <ulp.h>

  Instruction format structure.

  All ULP instructions are 32 bit long. This union contains field layouts used by all of the supported instructions. This union also includes a special "macro" instruction layout. This is not a real instruction which can be executed by the CPU. It acts as a token which is removed from the program by the ulp_process_macros_and_load function.

  These structures are not intended to be used directly. Preprocessor definitions provided below fill the fields of these structure with the right arguments.

  Public Members

  uint32_t cycles

    Number of cycles to sleep

    TBD, cycles used for measurement

  uint32_t unused

    Unused

  uint32_t opcode

    Opcode (OPCODE_DELAY)

    Opcode (OPCODE_ST)

    Opcode (OPCODE_LD)

    Opcode (OPCODE_HALT)

    Opcode (OPCODE_BRANCH)

    Opcode (OPCODE_ALU)

    Opcode (OPCODE_WR_REG)

    Opcode (OPCODE_RD_REG)

    Opcode (OPCODE_ADC)

    Opcode (OPCODE_TSENS)

    Opcode (OPCODE_I2C)

    Opcode (OPCODE_END)

    Opcode (OPCODE_MACRO)

  struct ulp_insn::[anonymous] delay

    Format of DELAY instruction

  uint32_t dreg

    Register which contains data to store

    Register where the data should be loaded to

    Register which contains target PC, expressed in words (used if .reg == 1)

    Destination register

    Register where to store ADC result

    Register where to store temperature measurement result

    Destination register (for SUB_OPCODE_MACRO_LABELPC) >

  uint32_t sreg

    Register which contains address in RTC memory (expressed in words)

    Register with operand A

  uint32_t unused1

    Unused

  uint32_t offset

    Offset to add to sreg

    Absolute value of target PC offset w.r.t. current PC, expressed in words

  uint32_t unused2

    Unused

  uint32_t sub_opcode

    Sub opcode (SUB_OPCODE_ST)

    Sub opcode (SUB_OPCODE_BX)

    Sub opcode (SUB_OPCODE_B)

    Sub opcode (SUB_OPCODE_BS)

    Sub opcode (SUB_OPCODE_ALU_REG)

    Sub opcode (SUB_OPCODE_ALU_CNT)

    Sub opcode (SUB_OPCODE_ALU_IMM)

    Sub opcode (SUB_OPCODE_WAKEUP)

    Sub opcode (SUB_OPCODE_SLEEP)

    SUB_OPCODE_MACRO_LABEL or SUB_OPCODE_MACRO_BRANCH or SUB_OPCODE_MACRO_LABELPC

  struct ulp_insn::[anonymous] st

    Format of ST instruction

  struct ulp_insn::[anonymous] ld

    Format of LD instruction

  struct ulp_insn::[anonymous] halt

    Format of HALT instruction

  uint32_t addr

    Target PC, expressed in words (used if .reg == 0)

    Address within either RTC_CNTL, RTC_IO, or SARADC

  uint32_t reg

    Target PC in register (1) or immediate (0)

  uint32_t type

    Jump condition (BX_JUMP_TYPE_xxx)

  struct ulp_insn::[anonymous] bx

    Format of BRANCH instruction (absolute address)

  uint32_t imm

    Immediate value to compare against

    Immediate value of operand

    Immediate value of operand B

  uint32_t cmp

    Comparison to perform: B_CMP_L or B_CMP_GE

    Comparison to perform: JUMPS_LT, JUMPS_GE or JUMPS_LE

  uint32_t sign

    Sign of target PC offset: 0: positive, 1: negative

  struct ulp_insn::[anonymous] b

    Format of BRANCH instruction (relative address, conditional on R0)

  struct ulp_insn::[anonymous] bs

    Format of BRANCH instruction (relative address, conditional on the stage counter)

  uint32_t treg

    Register with operand B

  uint32_t sel

    Operation to perform, one of ALU_SEL_xxx

    Operation to perform, one of ALU_SEL_Sxxx

  struct ulp_insn::[anonymous] alu_reg

    Format of ALU instruction (both sources are registers)

  struct ulp_insn::[anonymous] alu_reg_s

    Format of ALU instruction (stage counter and an immediate)

  struct ulp_insn::[anonymous] alu_imm

    Format of ALU instruction (one source is an immediate)

  uint32_t periph_sel

    Select peripheral: RTC_CNTL (0), RTC_IO(1), SARADC(2)

  uint32_t data

    8 bits of data to write

    8 bits of data for write operation

  uint32_t low

    Low bit

  uint32_t high

    High bit

  struct ulp_insn::[anonymous] wr_reg

    Format of WR_REG instruction

  struct ulp_insn::[anonymous] rd_reg

    Format of RD_REG instruction

  uint32_t mux

    Select SARADC pad (mux + 1)

  uint32_t sar_sel

    Select SARADC0 (0) or SARADC1 (1)

  struct ulp_insn::[anonymous] adc

    Format of ADC instruction

  uint32_t wait_delay

    Cycles to wait after measurement is done

  uint32_t reserved

    Reserved, set to 0

  struct ulp_insn::[anonymous] tsens

    Format of TSENS instruction

  uint32_t i2c_addr

    I2C slave address

  uint32_t low_bits

    low bit of range for write operation (lower bits are masked)

  uint32_t high_bits

    high bit of range for write operation (higher bits are masked)

  uint32_t i2c_sel

    index of slave address register [7:0]

  uint32_t rw

    Write (1) or read (0)

  struct ulp_insn::[anonymous] i2c

    Format of I2C instruction

  uint32_t wakeup

    Set to 1 to wake up chip

  struct ulp_insn::[anonymous] end

    Format of END instruction with wakeup

  uint32_t cycle_sel

    Select which one of SARADC_ULP_CP_SLEEP_CYCx_REG to get the sleep duration from

  struct ulp_insn::[anonymous] sleep

    Format of END instruction with sleep

  uint32_t label

    Label number

  struct ulp_insn::[anonymous] macro

    Format of tokens used by MACROs

  uint32_t instruction

    Encoded instruction for ULP coprocessor

### Macros

R0

  general purpose register 0

R1

  general purpose register 1

R2

  general purpose register 2

R3

  general purpose register 3

OPCODE_WR_REG

  Instruction: write peripheral register (RTC_CNTL/RTC_IO/SARADC)

OPCODE_RD_REG

  Instruction: read peripheral register (RTC_CNTL/RTC_IO/SARADC)

RD_REG_PERIPH_RTC_CNTL

  Identifier of RTC_CNTL peripheral for RD_REG and WR_REG instructions

RD_REG_PERIPH_RTC_IO

  Identifier of RTC_IO peripheral for RD_REG and WR_REG instructions

RD_REG_PERIPH_SENS

  Identifier of SARADC peripheral for RD_REG and WR_REG instructions

RD_REG_PERIPH_RTC_I2C

  Identifier of RTC_I2C peripheral for RD_REG and WR_REG instructions

OPCODE_I2C

  Instruction: read/write I2C

SUB_OPCODE_I2C_RD

  I2C read

SUB_OPCODE_I2C_WR

  I2C write

OPCODE_DELAY

  Instruction: delay (nop) for a given number of cycles

OPCODE_ADC

  Instruction: SAR ADC measurement

OPCODE_ST

  Instruction: store indirect to RTC memory

SUB_OPCODE_ST

  Store 32 bits, 16 MSBs contain PC, 16 LSBs contain value from source register

OPCODE_ALU

  Arithmetic instructions

SUB_OPCODE_ALU_REG

  Arithmetic instruction, both source values are in register

SUB_OPCODE_ALU_IMM

  Arithmetic instruction, one source value is an immediate

SUB_OPCODE_ALU_CNT

  Arithmetic instruction, stage counter and an immediate

ALU_SEL_ADD

  Addition

ALU_SEL_SUB

  Subtraction

ALU_SEL_AND

  Logical AND

ALU_SEL_OR

  Logical OR

ALU_SEL_MOV

  Copy value (immediate to destination register or source register to destination register

ALU_SEL_LSH

  Shift left by given number of bits

ALU_SEL_RSH

  Shift right by given number of bits

ALU_SEL_SINC

  Increment the stage counter

ALU_SEL_SDEC

  Decrement the stage counter

ALU_SEL_SRST

  Reset the stage counter

OPCODE_BRANCH

  Branch instructions

SUB_OPCODE_BX

  Branch to absolute PC (immediate or in register)

SUB_OPCODE_BR

  Branch to relative PC, conditional on R0

SUB_OPCODE_BS

  Branch to relative PC, conditional on the stage counter

BX_JUMP_TYPE_DIRECT

  Unconditional jump

BX_JUMP_TYPE_ZERO

  Branch if last ALU result is zero

BX_JUMP_TYPE_OVF

  Branch if last ALU operation caused and overflow

SUB_OPCODE_B

  Branch to a relative offset

B_CMP_L

  Branch if R0 is less than an immediate

B_CMP_GE

  Branch if R0 is greater than or equal to an immediate

JUMPS_LT

  Branch if the stage counter <

JUMPS_GE

  Branch if the stage counter >=

JUMPS_LE

  Branch if the stage counter <=

OPCODE_END

  Stop executing the program

SUB_OPCODE_END

  Stop executing the program and optionally wake up the chip

SUB_OPCODE_SLEEP

  Stop executing the program and run it again after selected interval

OPCODE_TSENS

  Instruction: temperature sensor measurement. Poor accuracy, not recommended for most use-cases

OPCODE_HALT

  Halt the coprocessor

OPCODE_LD

  Indirect load lower 16 bits from RTC memory

OPCODE_MACRO

  Not a real opcode. Used to identify labels and branches in the program

SUB_OPCODE_MACRO_LABEL

  Label macro

SUB_OPCODE_MACRO_BRANCH

  Branch macro

SUB_OPCODE_MACRO_LABELPC

  Label pointer macro

I_DELAY(cycles_)

  Delay (nop) for a given number of cycles

I_HALT()

  Halt the coprocessor.

  This instruction halts the coprocessor, but keeps ULP timer active. As such, ULP program will be restarted again by timer. To stop the program and prevent the timer from restarting the program, use I_END(0) instruction.

I_WR_REG(reg, low_bit, high_bit, val)

  Write literal value to a peripheral register

  reg[high_bit : low_bit] = val This instruction can access RTC_CNTL_, RTC_IO_, SENS_, and RTC_I2C peripheral registers.

I_RD_REG(reg, low_bit, high_bit)

  Read from peripheral register into R0

  R0 = reg[high_bit : low_bit] This instruction can access RTC_CNTL_, RTC_IO_, SENS_, and RTC_I2C peripheral registers.

I_WR_REG_BIT(reg, shift, val)

  Set or clear a bit in the peripheral register.

  Sets bit (1 << shift) of register reg to value val. This instruction can access RTC_CNTL_, RTC_IO_, SENS_, and RTC_I2C peripheral registers.

I_WAKE()

  Wake the SoC from deep sleep.

  This instruction initiates wake up from deep sleep. Use esp_deep_sleep_enable_ulp_wakeup to enable deep sleep wakeup triggered by the ULP before going into deep sleep. Note that ULP program will still keep running until the I_HALT instruction, and it will still be restarted by timer at regular intervals, even when the SoC is woken up.

  To stop the ULP program, use I_HALT instruction.

  To disable the timer which start ULP program, use I_END() instruction. I_END instruction clears the RTC_CNTL_ULP_CP_SLP_TIMER_EN_S bit of RTC_CNTL_STATE0_REG register, which controls the ULP timer.

I_END()

  Stop ULP program timer.

  This is a convenience macro which disables the ULP program timer. Once this instruction is used, ULP program will not be restarted anymore until ulp_run function is called.

  ULP program will continue running after this instruction. To stop the currently running program, use I_HALT().

I_SLEEP_CYCLE_SEL(timer_idx)

  Select the time interval used to run ULP program.

  This instructions selects which of the SENS_SLEEP_CYCLES_Sx registers' value is used by the ULP program timer. When the ULP program stops at I_HALT instruction, ULP program timer start counting. When the counter reaches the value of the selected SENS_SLEEP_CYCLES_Sx register, ULP program start running again from the start address (passed to the ulp_run function). There are 5 SENS_SLEEP_CYCLES_Sx registers, so 0 <= timer_idx < 5.

  By default, SENS_SLEEP_CYCLES_S0 register is used by the ULP program timer.

I_TSENS(reg_dest, delay)

  Perform temperature sensor measurement and store it into reg_dest.

  Delay can be set between 1 and ((1 << 14) - 1). Higher values give higher measurement resolution.

I_ADC(reg_dest, adc_idx, pad_idx)

  Perform ADC measurement and store result in reg_dest.

  adc_idx selects ADC (0 or 1). pad_idx selects ADC pad (0 - 7).

I_ST(reg_val, reg_addr, offset_)

  Store value from register reg_val into RTC memory.

  The value is written to an offset calculated by adding value of reg_addr register and offset_ field (this offset is expressed in 32-bit words). 32 bits written to RTC memory are built as follows:

  - bits [31:21] hold the PC of current instruction, expressed in 32-bit words

  - bits [20:18] = 3'b0

  - bits [17:16] reg_addr (0..3)

  - bits [15:0] are assigned the contents of reg_val

  RTC_SLOW_MEM[addr + offset_] = { insn_PC[10:0], 3'b0, reg_addr, reg_val[15:0] }

I_LD(reg_dest, reg_addr, offset_)

  Load value from RTC memory into reg_dest register.

  Loads 16 LSBs from RTC memory word given by the sum of value in reg_addr and value of offset_.

I_BL(pc_offset, imm_value)

  Branch relative if R0 less than immediate value.

  pc_offset is expressed in words, and can be from -127 to 127 imm_value is a 16-bit value to compare R0 against

I_BGE(pc_offset, imm_value)

  Branch relative if R0 greater or equal than immediate value.

  pc_offset is expressed in words, and can be from -127 to 127 imm_value is a 16-bit value to compare R0 against

I_BXR(reg_pc)

  Unconditional branch to absolute PC, address in register.

  reg_pc is the register which contains address to jump to. Address is expressed in 32-bit words.

I_BXI(imm_pc)

  Unconditional branch to absolute PC, immediate address.

  Address imm_pc is expressed in 32-bit words.

I_BXZR(reg_pc)

  Branch to absolute PC if ALU result is zero, address in register.

  reg_pc is the register which contains address to jump to. Address is expressed in 32-bit words.

I_BXZI(imm_pc)

  Branch to absolute PC if ALU result is zero, immediate address.

  Address imm_pc is expressed in 32-bit words.

I_BXFR(reg_pc)

  Branch to absolute PC if ALU overflow, address in register

  reg_pc is the register which contains address to jump to. Address is expressed in 32-bit words.

I_BXFI(imm_pc)

  Branch to absolute PC if ALU overflow, immediate address

  Address imm_pc is expressed in 32-bit words.

I_ADDR(reg_dest, reg_src1, reg_src2)

  Addition: dest = src1 + src2

I_SUBR(reg_dest, reg_src1, reg_src2)

  Subtraction: dest = src1 - src2

I_ANDR(reg_dest, reg_src1, reg_src2)

  Logical AND: dest = src1 & src2

I_ORR(reg_dest, reg_src1, reg_src2)

  Logical OR: dest = src1 | src2

I_MOVR(reg_dest, reg_src)

  Copy: dest = src

I_LSHR(reg_dest, reg_src, reg_shift)

  Logical shift left: dest = src << shift

I_RSHR(reg_dest, reg_src, reg_shift)

  Logical shift right: dest = src >> shift

I_ADDI(reg_dest, reg_src, imm_)

  Add register and an immediate value: dest = src1 + imm

I_SUBI(reg_dest, reg_src, imm_)

  Subtract register and an immediate value: dest = src - imm

I_ANDI(reg_dest, reg_src, imm_)

  Logical AND register and an immediate value: dest = src & imm

I_ORI(reg_dest, reg_src, imm_)

  Logical OR register and an immediate value: dest = src | imm

I_MOVI(reg_dest, imm_)

  Copy an immediate value into register: dest = imm

I_LSHI(reg_dest, reg_src, imm_)

  Logical shift left register value by an immediate: dest = src << imm

I_RSHI(reg_dest, reg_src, imm_)

  Logical shift right register value by an immediate: dest = val >> imm

M_LABEL(label_num)

  Define a label with number label_num.

  This is a macro which doesn't generate a real instruction. The token generated by this macro is removed by ulp_process_macros_and_load function. Label defined using this macro can be used in branch macros defined below.

M_BRANCH(label_num)

  Token macro used by M_B and M_BX macros. Not to be used directly.

M_LABELPC(label_num)

  Token macro used by M_MOVL macro. Not to be used directly.

M_MOVL(reg_dest, label_num)

  Macro: Move the program counter at the given label into the register. This address can then be used with I_BXR, I_BXZR, I_BXFR, etc.

  This macro generates two ulp_insn_t values separated by a comma, and should be used when defining contents of ulp_insn_t arrays. First value is not a real instruction; it is a token which is removed by ulp_process_macros_and_load function.

M_BL(label_num, imm_value)

  Macro: branch to label label_num if R0 is less than immediate value.

  This macro generates two ulp_insn_t values separated by a comma, and should be used when defining contents of ulp_insn_t arrays. First value is not a real instruction; it is a token which is removed by ulp_process_macros_and_load function.

M_BGE(label_num, imm_value)

  Macro: branch to label label_num if R0 is greater or equal than immediate value

  This macro generates two ulp_insn_t values separated by a comma, and should be used when defining contents of ulp_insn_t arrays. First value is not a real instruction; it is a token which is removed by ulp_process_macros_and_load function.

M_BX(label_num)

  Macro: unconditional branch to label

  This macro generates two ulp_insn_t values separated by a comma, and should be used when defining contents of ulp_insn_t arrays. First value is not a real instruction; it is a token which is removed by ulp_process_macros_and_load function.

M_BXZ(label_num)

  Macro: branch to label if ALU result is zero

  This macro generates two ulp_insn_t values separated by a comma, and should be used when defining contents of ulp_insn_t arrays. First value is not a real instruction; it is a token which is removed by ulp_process_macros_and_load function.

M_BXF(label_num)

  Macro: branch to label if ALU overflow

  This macro generates two ulp_insn_t values separated by a comma, and should be used when defining contents of ulp_insn_t arrays. First value is not a real instruction; it is a token which is removed by ulp_process_macros_and_load function.

I_STAGE_INC(imm_)

  Increment the stage counter by immediate value

I_STAGE_DEC(imm_)

  Decrement the stage counter by immediate value

I_STAGE_RST()

  Reset the stage counter

M_BSLT(label_num, imm_value)

  Macro: branch to label if the stage counter is less than immediate value

  This macro generates two ulp_insn_t values separated by a comma, and should be used when defining contents of ulp_insn_t arrays. First value is not a real instruction; it is a token which is removed by ulp_process_macros_and_load function.

M_BSGE(label_num, imm_value)

  Macro: branch to label if the stage counter is greater than or equal to immediate value

  This macro generates two ulp_insn_t values separated by a comma, and should be used when defining contents of ulp_insn_t arrays. First value is not a real instruction; it is a token which is removed by ulp_process_macros_and_load function.

M_BSLE(label_num, imm_value)

  Macro: branch to label if the stage counter is less than or equal to immediate value

  This macro generates two ulp_insn_t values separated by a comma, and should be used when defining contents of ulp_insn_t arrays. First value is not a real instruction; it is a token which is removed by ulp_process_macros_and_load function.

M_BSEQ(label_num, imm_value)

  Macro: branch to label if the stage counter is equal to immediate value. Implemented using two JUMPS instructions: JUMPS next, imm_value, LT JUMPS label_num, imm_value, LE

  This macro generates three ulp_insn_t values separated by commas, and should be used when defining contents of ulp_insn_t arrays. Second value is not a real instruction; it is a token which is removed by ulp_process_macros_and_load function.

M_BSGT(label_num, imm_value)

  Macro: branch to label if the stage counter is greater than immediate value. Implemented using two instructions: JUMPS next, imm_value, LE JUMPS label_num, imm_value, GE

  This macro generates three ulp_insn_t values separated by commas, and should be used when defining contents of ulp_insn_t arrays. Second value is not a real instruction; it is a token which is removed by ulp_process_macros_and_load function.

I_JUMPS(pc_offset, imm_value, comp_type)

  Branch relative if (stage counter [comp_type] [imm_value]) evaluates to true.

  pc_offset is expressed in words, and can be from -127 to 127 imm_value is an 8-bit value to compare the stage counter against comp_type is the type of comparison to perform: JUMPS_LT (<), JUMPS_GE (>=) or JUMPS_LE (<=)

I_I2C_RW(sub_addr, val, low_bit, high_bit, slave_sel, rw_bit)

  Perform an I2C transaction with a slave device. I_I2C_READ and I_I2C_WRITE are provided for convenience, instead of using this directly.

  Slave address (in 7-bit format) has to be set in advance into SENS_I2C_SLAVE_ADDRx register field, where x == slave_sel. For read operations, 8 bits of read result is stored into R0 register. For write operations, val will be written to sub_addr at [high_bit:low_bit]. Bits outside of this range are masked.

I_I2C_READ(slave_sel, sub_addr)

  Read a byte from the sub address of an I2C slave, and store the result in R0.

  Slave address (in 7-bit format) has to be set in advance into SENS_I2C_SLAVE_ADDRx register field, where x == slave_sel.

I_I2C_WRITE(slave_sel, sub_addr, val)

  Write a byte to the sub address of an I2C slave.

  Slave address (in 7-bit format) has to be set in advance into SENS_I2C_SLAVE_ADDRx register field, where x == slave_sel.

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