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MCP23017 module refactorings to save some heap #3317

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Oct 29, 2020
Merged

MCP23017 module refactorings to save some heap #3317

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841be03
mcp23017: functions to metatable
nwf Oct 25, 2020
612c1ca
mcp23017: inline constants
nwf Oct 25, 2020
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204 changes: 87 additions & 117 deletions lua_modules/mcp23017/mcp23017.lua
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Original file line number Diff line number Diff line change
@@ -1,62 +1,40 @@
--[[
This Lua module provides access to the MCP23017 module.
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).
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.
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 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.
The module requires `i2c` and `bit` C module built into firmware.

@author Marcel P. | Plomi.net
@github https://github.com/plomi-net
@version 1.0.0
]]
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.

local i2c, string, issetBit, setBit, clearBit, error =
i2c, string, bit.isset, bit.set, bit.clear, error
local isINPUT, isGPB, isHIGH = true, true, true

-- registers (not used registers are commented out)
local MCP23017_IODIRA = 0x00
local MCP23017_IODIRB = 0x01
local MCP23017_DEFVALA = 0x06
local MCP23017_DEFVALB = 0x07
local MCP23017_GPIOA = 0x12
local MCP23017_GPIOB = 0x13
--[[
local MCP23017_IPOLA = 0x02
local MCP23017_IPOLB = 0x03
local MCP23017_GPINTENA = 0x04
local MCP23017_GPINTENB = 0x05
local MCP23017_DEFVALA = 0x06
local MCP23017_DEFVALB = 0x07
local MCP23017_INTCONA = 0x08
local MCP23017_INTCONB = 0x09
local MCP23017_IOCON = 0x0A
local MCP23017_IOCON2 = 0x0B
local MCP23017_GPPUA = 0x0C
local MCP23017_GPPUB = 0x0D
local MCP23017_INTFA = 0x0E
local MCP23017_INTFB = 0x0F
local MCP23017_INTCAPA = 0x10
local MCP23017_INTCAPB = 0x11
local MCP23017_OLATA = 0x14
local MCP23017_OLATB = 0x15
@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 = {
INPUT = isINPUT,
OUTPUT = not isINPUT,
GPA = not isGPB,
GPB = isGPB,
HIGH = isHIGH,
LOW = not isHIGH
-- convenience parameter enumeration names
INPUT = true,
OUTPUT = false,
GPA = false,
GPB = true,
HIGH = true,
LOW = false
}
mcp23017.__index = mcp23017

Expand Down Expand Up @@ -98,13 +76,65 @@ local function checkPinIsInRange(pin)
return pin
end

local function reset(address, i2cId)
writeByte(address, i2cId, MCP23017_IODIRA, 0xFF)
writeByte(address, i2cId, MCP23017_IODIRB, 0xFF)
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

-- setup device
local function setup(address, i2cId)
-- 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
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I think that if the module fails to setup properly (fail in address range check or in checkDevice) it should return nil like in the previous version of the code - without that it's possible to setup module with address out of possible range and that definitely shouldn't return the same thing as correctly initialized module.

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Sorry, I think I am misunderstanding your comment. The version of the code now in dev errors out in these cases; it did not, AFAICT, "return nil" despite appearances: setup never returned false. This patch preserves those behaviors (or, well, is at least meant to; did I break something?).

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setup never returned false

I missed it completely! Now I wonder if that should be the case - if the module is not initialised correctly then it shouldn't return the same thing as correctly initialized one. It this a desired behaviour @plomi-net ? I think this can both use error and return nil but that would be up to discussion.

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This looks like a mistake. Of course, in case of error nil can be returned. I assumed that throwing an error would be enough.

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I am inclined to think that throwing an error is also enough, yes.

Expand All @@ -113,73 +143,13 @@ local function setup(address, i2cId)

if (checkDevice(address, i2cId) ~= true) then
error("MCP23017 device on " .. string.format('0x%02X', address) .. " not found")
else
reset(address, i2cId)
return 1
end
end

return function(address, i2cId)
local self = setmetatable({}, mcp23017)
self.address = address
self.i2cId = i2cId

if setup(address, i2cId) then
self.writeIODIR = function(sf, bReg, newByte) -- luacheck: no unused
writeByte(address, i2cId,
bReg == isGPB and MCP23017_IODIRB or MCP23017_IODIRA,
newByte)
end

self.writeGPIO = function(sf, bReg, newByte) -- luacheck: no unused
writeByte(address, i2cId,
bReg == isGPB and MCP23017_GPIOB or MCP23017_GPIOA, newByte)
end

self.readGPIO = function(sf, bReg) -- luacheck: no unused
return readByte(address, i2cId, -- upvals
bReg == isGPB and MCP23017_GPIOB or MCP23017_GPIOA)
end

-- read pin input
self.getPinState = function(sf, bReg, pin) -- luacheck: no unused
return issetBit(readByte(address, i2cId,
bReg == isGPB and MCP23017_GPIOB or MCP23017_GPIOA),
checkPinIsInRange(pin))
end

-- set pin to low or high
self.setPin = function(sf, bReg, pin, state) -- luacheck: no unused
local inReq = bReg == isGPB and MCP23017_GPIOB or MCP23017_GPIOA
local inPin = checkPinIsInRange(pin)
local response = readByte(address, i2cId, inReq)
writeByte(address, i2cId, inReq,
state == isHIGH and setBit(response, inPin) or clearBit(response, inPin))
return true
end

-- set mode for a pin
self.setMode = function(sf, bReg, pin, mode) -- luacheck: no unused
local inReq = bReg == isGPB and MCP23017_IODIRB or MCP23017_IODIRA
local inPin = checkPinIsInRange(pin)
local response = readByte(address, i2cId, inReq)
writeByte(address, i2cId, inReq,
mode == isINPUT and setBit(response, inPin) or clearBit(response, inPin))
return true
end

-- reset gpio mode
self.reset = function(sf) -- luacheck: no unused
reset(address, i2cId)
end

-- setup internal pullup
self.setInternalPullUp = function(sf, bReg, iByte) -- luacheck: no unused
writeByte(address, i2cId,
bReg == isGPB and MCP23017_DEFVALB or MCP23017_DEFVALA, iByte)
end

return self
end
return nil
self:reset()
return self
end