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- --[[
- This Lua module provides access to the MCP23017 module.
- The MCP23017 is a port expander and provides 16 channels for inputs and
- outputs. Up to 8 devices (128 channels) are possible by the configurable
- address (A0 - A2 Pins).
- Due to the 16 channels, 2 bytes are required for switching outputs or
- reading input signals. These are A and B. A single pin can be set or a
- whole byte.
- The numbering of the individual pins starts at 0 and ends with 7. The
- numbers are for each register GPIO A and GPIO B.
- The module requires `i2c` and `bit` C module built into firmware.
- For register name <-> number mapping, see the MCP23017 data sheet, table
- 3-1 on page 12 (as of Revision C, July 2016). This module uses the
- IOCON.BANK=0 numbering (the default) throughout.
- @author Marcel P. | Plomi.net
- @github https://github.com/plomi-net
- @version 1.0.0
- ]]
- local i2c, string, issetBit, setBit, clearBit =
- i2c, string, bit.isset, bit.set, bit.clear
- -- metatable
- local mcp23017 = {
- -- convenience parameter enumeration names
- INPUT = true,
- OUTPUT = false,
- GPA = false,
- GPB = true,
- HIGH = true,
- LOW = false
- }
- mcp23017.__index = mcp23017
- -- check device is available on address
- local function checkDevice(address, i2cId)
- i2c.start(i2cId)
- local response = i2c.address(i2cId, address, i2c.TRANSMITTER)
- i2c.stop(i2cId)
- return response
- end
- -- write byte
- local function writeByte(address, i2cId, registerAddr, val)
- i2c.start(i2cId)
- i2c.address(i2cId, address, i2c.TRANSMITTER)
- i2c.write(i2cId, registerAddr)
- i2c.write(i2cId, val)
- i2c.stop(i2cId)
- end
- -- read byte
- local function readByte(address, i2cId, registerAddr)
- i2c.start(i2cId)
- i2c.address(i2cId, address, i2c.TRANSMITTER)
- i2c.write(i2cId, registerAddr)
- i2c.stop(i2cId)
- i2c.start(i2cId)
- i2c.address(i2cId, address, i2c.RECEIVER)
- local data = i2c.read(i2cId, 1)
- i2c.stop(i2cId)
- return string.byte(data)
- end
- -- check pin is in range
- local function checkPinIsInRange(pin)
- if pin > 7 or pin < 0 then
- error("MCP23017 the pin must be between 0 and 7")
- end
- return pin
- end
- function mcp23017:writeIODIR(bReg, newByte)
- writeByte(self.address, self.i2cId,
- bReg and 0x1 --[[IODIRB register]] or 0x0 --[[IODIRA register]], newByte)
- end
- function mcp23017:writeGPIO(bReg, newByte)
- writeByte(self.address, self.i2cId,
- bReg and 0x13 --[[GPIOB register]] or 0x12 --[[GPIOA register]], newByte)
- end
- function mcp23017:readGPIO(bReg)
- return readByte(self.address, self.i2cId,
- bReg and 0x13 --[[GPIOB register]] or 0x12 --[[GPIOA register]])
- end
- -- read pin input
- function mcp23017:getPinState(bReg, pin)
- return issetBit(readByte(self.address, self.i2cId,
- bReg and 0x13 --[[GPIOB register]] or 0x12 --[[GPIOA register]]),
- checkPinIsInRange(pin))
- end
- -- set pin to low or high
- function mcp23017:setPin(bReg, pin, state)
- local a, i = self.address, self.i2cId
- local inReq = bReg and 0x13 --[[GPIOB register]] or 0x12 --[[GPIOA register]]
- local inPin = checkPinIsInRange(pin)
- local response = readByte(a, i, inReq)
- writeByte(a, i, inReq,
- state and setBit(response, inPin) or clearBit(response, inPin))
- return true
- end
- -- set mode for a pin
- function mcp23017:setMode(bReg, pin, mode)
- local a, i = self.address, self.i2cId
- local inReq = bReg and 0x1 --[[IODIRB register]] or 0x0 --[[IODIRA register]]
- local inPin = checkPinIsInRange(pin)
- local response = readByte(a, i, inReq)
- writeByte(a, i, inReq,
- mode and setBit(response, inPin) or clearBit(response, inPin))
- return true
- end
- -- reset gpio mode
- function mcp23017:reset()
- local a, i = self.address, self.i2cId
- writeByte(a, i, 0x0 --[[IODIRA register]], 0xFF)
- writeByte(a, i, 0x1 --[[IODIRB register]], 0xFF)
- end
- -- setup internal pullup
- function mcp23017:setInternalPullUp(bReg, iByte)
- writeByte(self.address, self.i2cId,
- bReg and 0x7 --[[DEFVALB register]] or 0x6 --[[DEFVALA register]], iByte)
- end
- return function(address, i2cId)
- local self = setmetatable({}, mcp23017)
- -- check device address (0x20 to 0x27)
- if (address < 32 or address > 39) then
- error("MCP23017 address is out of range")
- end
- if (checkDevice(address, i2cId) ~= true) then
- error("MCP23017 device on " .. string.format('0x%02X', address) .. " not found")
- end
- self.address = address
- self.i2cId = i2cId
- self:reset()
- return self
- end
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