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;
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;
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; Copyright 2012, Sinclair R.F., Inc.
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; Copyright 2012, 2014, Sinclair R.F., Inc.
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;
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;
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; Major I2C functions:
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; Major I2C functions:
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; i2c_send_start ( - )
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; i2c_send_start ( - ) send the start condition
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; i2c_send_byte ( u - f )
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; i2c_send_restart ( - ) send a restart after ACK during write
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; i2c_read_byte ( - u )
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; i2c_send_byte ( u - f ) send a byte (address, register, data, ...)
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; i2c_send_stop ( - )
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; i2c_read_byte ( f - u ) read a byte and either ACK (f=0) or STOP (f=1)
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; i2c_send_stop ( - ) send a stop after ACK during write
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;
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; Example to set a single register (ignoring returned ACK/NACK value)
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; .call(i2c_send_start)
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; .call(i2c_send_byte,write_address) drop
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; .call(i2c_send_byte,register) drop
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; .call(i2c_send_byte,data) drop
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; .call(i2c_send_stop)
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;
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; Example to read two bytes (ignoring returned ACK/NACK value)
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; .call(i2c_send_start)
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; .call(i2c_send_byte,write_address) drop
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; .call(i2c_send_byte,register) drop
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; .call(i2c_send_restart)
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; .call(i2c_send_byte,read_address) drop
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; .call(i2c_read_byte,0)
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; .call(i2c_read_byte,1)
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;
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;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; Compute how many iterations in the quarter-clock-cycle function are required.
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; Compute how many iterations in the quarter-clock-cycle function are required.
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; ceil(100 MHz / 400 kHz / 4) ==> 63 clock cycles per I2C SCL quarter cycle
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; ceil(100 MHz / 400 kHz / 4) ==> 63 clock cycles per I2C SCL quarter cycle
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; 1 clock cycle to initialize the loop count
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; 1 clock cycle to initialize the loop count
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; 2 clock cycles to return
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; 2 clock cycles to return
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; 9 TOTAL
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; 9 TOTAL
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; Add 2 to ensure rounding up when evaluting the integer fraction.
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; Add 2 to ensure rounding up when evaluting the integer fraction.
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; The loop is 3 clock cycles per iteration
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; The loop is 3 clock cycles per iteration
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.IFNDEF C_I2C_QUARTER_CYCLE
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.constant C_I2C_QUARTER_CYCLE ${(63-9+2)/3}
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.constant C_I2C_QUARTER_CYCLE ${(63-9+2)/3}
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.ENDIF
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; ( - )
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; ( - )
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.function i2c_send_start
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.function i2c_send_start
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0 .outport(O_SDA)
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0 .outport(O_SDA)
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.call(i2c_quarter_cycle,1)
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.call(i2c_quarter_cycle,1)
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; get the acknowledge bit at the middle of the high portion of SCL
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; get the acknowledge bit at the middle of the high portion of SCL
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; ( - f )
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; ( - f )
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.call(i2c_clock_cycle,1)
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.call(i2c_clock_cycle,1)
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.return
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.return
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; Read the next byte from the device.
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; Read the next byte from the device and generate an ACK or a STOP.
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; ( - u )
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; ( f - u )
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.function i2c_read_byte
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.function i2c_read_byte
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; Read 8 bits and pack them into the returned value.
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; ( f - u f )
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0 ${8-1} :loop
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0 ${8-1} :loop
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swap <<0 .call(i2c_clock_cycle,1) or swap
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swap <<0 .call(i2c_clock_cycle,1) or swap
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.jumpc(loop,1-) drop
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.jumpc(loop,1-) drop
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; send the acknowledgment bit
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swap
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.call(i2c_clock_cycle,0)
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; Generate the ACK/STOP based on f.
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.return(drop)
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; ( u f - u )
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0 .outport(O_SDA)
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.call(i2c_quarter_cycle,0)
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.call(i2c_quarter_cycle,1)
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O_SDA outport
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.call(i2c_quarter_cycle,1)
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.call(i2c_quarter_cycle) ; SCL is high on STOP, low on ACK, consumes f
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.return
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; Send a stop by bringing SDA high while SCL is high.
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; Send a stop by bringing SDA high while SCL is high.
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; ( - )
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; ( - )
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.function i2c_send_stop
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.function i2c_send_stop
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0 .outport(O_SDA) .call(i2c_quarter_cycle,0)
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0 .outport(O_SDA) .call(i2c_quarter_cycle,0)
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