246 lines
16 KiB
Plaintext
246 lines
16 KiB
Plaintext
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{{┌──────────────────────────────────────────┐
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│ I2C slave object │
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│ Author: Chris Gadd │
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│ Copyright (c) 2013 Chris Gadd │
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│ See end of file for terms of use. │
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└──────────────────────────────────────────┘
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This object creates an I2C slave device with 32 byte-sized registers on the Propeller, which an I2C master device can read from and write to using standard protocol:
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7-bit device ID + read/write bit, 8-bit register address, 8 bits of data
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Supports single, repeated, and page reads and writes
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Does NOT check for overruns - Writing 5 bytes starting at register 31 may produce unexpected results
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To use:
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slave.start(28,29,$42) Start the slave object using p28 for clock, p29 for data, with device ID $42
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slave.check Returns the index (31-0) of the highest byte in the register that was written to by a master
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Subsequent calls to slave.check return the index of the next highest byte with new data
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slave.check_reg(5) Returns the contents of register 5 only if the new-data flag for that register is set, returns -1 otherwise
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slave.get(10) Returns the value of register 10
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slave.put(11,#2) Stores the value 2 in register 11
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slave.flush Clears all 32 registers to 0
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slave.address Returns the base address of the slave registers - useful for directly operating on the registers
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by higher-level objects
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Tested up to 769Kbps (max transmit speed of the master object)
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}}
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VAR
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long flags ' Used to determine if a register has new data from the master
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byte _slave_address
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byte SCL_pin
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byte SDA_pin
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byte register[32]
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byte cog
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PUB start(clk_pin, data_pin, slave_address) : okay
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stop
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_slave_address := slave_address
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SCL_pin := clk_pin
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SDA_pin := data_pin
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okay := cog := cognew(@entry, @flags) + 1
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PUB stop
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if cog
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cogstop(cog~ - 1)
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PUB address
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return @register
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PUB check : index
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{{
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Returns the number of the highest byte that was written to:
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If an I2C master wrote to addresses 3 and 7 of the slave's buffer, #7 is returned
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The flag for the highest byte is then cleared, so a subsequent check would return #3
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Returns -1 if all updated byte addresses have been returned (no new data)
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}}
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index := (>| flags) - 1
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flags := flags & !(|< index) ' Clear the highest set bit
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PUB check_reg(index)
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{{
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Returns the value of the indexed register if that register has new data
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Returns -1 otherwise
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}}
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if |< index & flags
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flags := flags & !(|< index)
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return register[index]
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return -1
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PUB get(index)
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return register[index]
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PUB put(index,data)
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register[index] := data
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PUB flush | i
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flags~
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repeat i from 0 to 31
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register[i]~
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DAT org
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entry
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mov t1,par
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mov flags_address,t1 ' Retrieve all of the addresses and
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add t1,#4 ' pin assignments from the VAR block,
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rdbyte device_address,t1 ' and create bit masks
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shl device_address,#1
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add t1,#1
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rdbyte t2,t1
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mov SCL_mask,#1
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shl SCL_mask,t2
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add t1,#1
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rdbyte t2,t1
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mov SDA_mask,#1
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shl SDA_mask,t2
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add t1,#1
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mov register_address,t1
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mov idle_mask,SCL_mask
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or idle_mask,SDA_mask
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'----------------------------------------------------------------------------------------------------------------------
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main
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call #wait_for_start
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start_detected
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call #receive
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mov t1,I2C_byte
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and t1,#%1111_1110 ' clear the read/write flag and compare received
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cmp t1,device_address wz ' device address with assigned address
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if_ne jmp #main
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call #ack
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test I2C_byte,#%0000_0001 wc ' test read(1) or write(0) bit of device address
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if_nc jmp #write
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read '(from_master)
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call #respond ' The master sends an ACK or NAK in response to
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add data_address,#1 ' every byte sent back from the slave
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if_nc jmp #read ' Send another byte if ACK (c=0)
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jmp #main ' Stop if NAK (c=1)
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write '(from_master)
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rdlong t1,flags_address ' Use t1 to hold all flags
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mov t2,#1 ' Use t2 to hold the flag of the current register
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mov data_address,register_address ' Prepare the to store new data
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call #receive ' First byte received is a register address
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add data_address,I2C_byte
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shl t2,I2C_byte ' Shift the flag to the appropriate register
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call #ack
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:loop
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call #receive ' Receive a data byte
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wrbyte I2C_byte,data_address ' Store in the addressed register
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add data_address,#1 ' Address the next register
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or t1,t2 ' Update the flags
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wrlong t1,flags_address
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shl t2,#1 ' Shift the flag to the next register
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call #ack
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jmp #:loop
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'======================================================================================================================
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wait_for_start ' SCL
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waitpeq idle_mask,idle_mask ' SDA
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:loop
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waitpne SDA_mask,SDA_mask
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test SCL_mask,ina wc
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if_nc jmp #wait_for_start
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wait_for_start_ret ret
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'----------------------------------------------------------------------------------------------------------------------
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receive ' (Read)
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mov loop_counter,#8 '
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mov I2C_byte,#0 ' SCL
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:loop ' SDA ───────
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waitpne SCL_mask,SCL_mask
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waitpeq SCL_mask,SCL_mask
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test SDA_mask,ina wc
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rcl I2C_byte,#1
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call #detect_st_or_sp ' Check to see if the received bit is a stop or restart
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djnz loop_counter,#:loop
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receive_ret ret
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'----------------------------------------------------------------------------------------------------------------------
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respond ' (Write) (Read ACK or NAK)
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mov loop_counter,#8 '
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rdbyte I2C_byte,data_address ' SCL
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shl I2C_byte,#32-8 ' SDA ───────
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:loop
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waitpne SCL_mask,SCL_mask
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shl I2C_byte,#1 wc
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muxnc dira,SDA_mask
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waitpeq SCL_mask,SCL_mask
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waitpne SCL_mask,SCL_mask
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djnz loop_counter,#:loop
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andn dira,SDA_mask
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'receive_ack_or_nak
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waitpne SCL_mask,SCL_mask
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waitpeq SCL_mask,SCL_mask
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test SDA_mask,ina wc ' C is set if NAK
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call #detect_st_or_sp
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respond_ret ret
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'----------------------------------------------------------------------------------------------------------------------
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ack ' SCL
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waitpne SCL_mask,SCL_mask ' SDA
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or dira,SDA_mask
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waitpeq SCL_mask,SCL_mask
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waitpne SCL_mask,SCL_mask
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andn dira,SDA_mask
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ack_ret ret
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'----------------------------------------------------------------------------------------------------------------------
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nak ' SCL
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waitpne SCL_mask,SCL_mask ' SDA
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waitpeq SCL_mask,SCL_mask
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call #detect_st_or_sp
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waitpne SCL_mask,SCL_mask
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nak_ret ret
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'----------------------------------------------------------------------------------------------------------------------
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detect_st_or_sp
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' test SDA_mask,ina wc ' routine is called with C already set to SDA
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if_c jmp #:detect_restart
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:detect_stop ' SCL
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test SCL_mask,ina wz ' SDA
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if_z jmp detect_st_or_sp_ret
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test SDA_mask,ina wz
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if_nz jmp #main
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jmp #:detect_stop
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:detect_restart ' SCL
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test SCL_mask,ina wz ' SDA
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if_z jmp detect_st_or_sp_ret
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test SDA_mask,ina wz
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if_z jmp #start_detected
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jmp #:detect_restart
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detect_st_or_sp_ret ret
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'----------------------------------------------------------------------------------------------------------------------
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SCL_mask res 1
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SDA_mask res 1
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idle_mask res 1
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device_address res 1
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register_address res 1
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data_address res 1
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flags_address res 1
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I2C_byte res 1
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loop_counter res 1
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t1 res 1
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t2 res 1
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fit
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DAT
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{{
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┌──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
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│ TERMS OF USE: MIT License │
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├──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
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│Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation │
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│files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, │
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│modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software│
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│is furnished to do so, subject to the following conditions: │
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│ │
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│The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.│
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│ │
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│THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE │
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│WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR │
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│COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, │
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│ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. │
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└──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
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}}
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