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jm_i2c.spin
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jm_i2c.spin
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'' ================================================================================================='''' File....... jm_i2c.spin'' Purpose.... Low-level I2C routines (requires pull-ups on SCL and SDA)'' Author..... Jon "JonnyMac" McPhalen'' Copyright (c) 2009-2014 Jon McPhalen'' -- elements inspired by code from Mike Green'' E-mail..... '' Started.... 28 JUL 2009'' Updated.... 06 APR 2014'''' =================================================================================================' IMPORTANT Note: This code requires pull-ups on the SDA _and_ SCL lines -- it does not drive' the SCL line high.con { fixed io pins } RX1 = 31 ' programming / debug port TX1 = 30 EE_SDA = 29 ' eeprom EE_SCL = 28 con #0, ACK, NAK var long scl ' buss pins long sda pub setup '' Setup I2C using Propeller EEPROM pins setupx(EE_SCL, EE_SDA) pub setupx(sclpin, sdapin)'' Define I2C SCL (clock) and SDA (data) pins longmove(@scl, @sclpin, 2) ' copy pins dira[scl] := 0 ' float to pull-up outa[scl] := 0 ' write 0 to output reg dira[sda] := 0 outa[sda] := 0 repeat 9 ' reset device dira[scl] := 1 dira[scl] := 0 if (ina[sda]) quit pub present(ctrl)'' Pings device, returns true it ACK start return (write(ctrl) == ACK) pub wait(ctrl) | ackbit'' Waits for I2C device to be ready for new command repeat start ackbit := write(ctrl) until (ackbit == ACK)pub start '' Create I2C start sequence'' -- will wait if I2C buss SDA pin is held low dira[sda] := 0 ' float SDA (1) dira[scl] := 0 ' float SCL (1) repeat while (ina[scl] == 0) ' allow "clock stretching" dira[sda] := 1 ' SDA low (0) dira[scl] := 1 ' SCL low (0) pub write(i2cbyte) | ackbit'' Write byte to I2C buss'' -- leaves SCL low i2cbyte := (i2cbyte ^ $FF) << 24 ' move msb (bit7) to bit31 repeat 8 ' output eight bits dira[sda] := i2cbyte <-= 1 ' send msb first dira[scl] := 0 ' SCL high (float to p/u) dira[scl] := 1 ' SCL low dira[sda] := 0 ' relase SDA to read ack bit dira[scl] := 0 ' SCL high (float to p/u) ackbit := ina[sda] ' read ack bit dira[scl] := 1 ' SCL low return ackbitpub read(ackbit) | i2cbyte'' Read byte from I2C buss dira[sda] := 0 ' make sda input repeat 8 dira[scl] := 0 ' SCL high (float to p/u) i2cbyte := (i2cbyte << 1) | ina[sda] ' read the bit dira[scl] := 1 ' SCL low dira[sda] := !ackbit ' output ack bit dira[scl] := 0 ' clock it dira[scl] := 1 return (i2cbyte & $FF)pub stop'' Create I2C stop sequence dira[sda] := 1 ' SDA low dira[scl] := 0 ' float SCL repeat until (ina[scl] == 1) ' hold for clock stretch dira[sda] := 0 ' float SDAdat{{ Terms of Use: MIT License Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. }}