110 lines
3.8 KiB
Lua
110 lines
3.8 KiB
Lua
local i2c, bit = i2c, bit --luacheck: read globals i2c bit
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return function(bus_args)
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local busid = bus_args.id or 0
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local busad = bus_args.address or 0x27
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local speed = bus_args.speed or i2c.SLOW
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local rs = bus_args.rs or 0
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local rw = bus_args.rw or 1
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local en = bus_args.en or 2
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local bl = bus_args.backlight or 3
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local d4 = bus_args.d4 or 4
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local d5 = bus_args.d5 or 5
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local d6 = bus_args.d6 or 6
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local d7 = bus_args.d7 or 7
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-- Convenience I2C setup if a pin configuration is given
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if bus_args.sda ~= nil and bus_args.scl ~= nil then
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i2c.setup(busid, bus_args.sda, bus_args.scl, speed)
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end
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-- The onus is on us to maintain the backlight state
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local backlight = true
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local function exchange(data, read)
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local rv = data
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i2c.start(busid)
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i2c.address(busid, busad, i2c.TRANSMITTER)
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i2c.write(busid, bit.set(data, en)) -- set data with en
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if read then
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i2c.start(busid) -- read 1 byte and go back to tx mode
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i2c.address(busid, busad, i2c.RECEIVER)
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rv = i2c.read(busid, 1):byte(1)
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i2c.start(busid)
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i2c.address(busid, busad, i2c.TRANSMITTER)
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end
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i2c.write(busid, data) -- lower en
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i2c.stop(busid)
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return rv
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end
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local function send4bitI2C(value, rs_en, rw_en)
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local meta = bit.bor(rs_en and bit.bit(rs) or 0,
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rw_en and bit.bit(rw) or 0,
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backlight and bit.bit(bl) or 0)
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local lo = bit.bor(bit.isset(value, 0) and bit.bit(d4) or 0,
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bit.isset(value, 1) and bit.bit(d5) or 0,
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bit.isset(value, 2) and bit.bit(d6) or 0,
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bit.isset(value, 3) and bit.bit(d7) or 0)
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local hi = bit.bor(bit.isset(value, 4) and bit.bit(d4) or 0,
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bit.isset(value, 5) and bit.bit(d5) or 0,
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bit.isset(value, 6) and bit.bit(d6) or 0,
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bit.isset(value, 7) and bit.bit(d7) or 0)
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hi = exchange(bit.bor(meta, hi), rw_en)
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lo = exchange(bit.bor(meta, lo), rw_en)
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return bit.bor(bit.lshift(bit.isset(lo, d4) and 1 or 0, 0),
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bit.lshift(bit.isset(lo, d5) and 1 or 0, 1),
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bit.lshift(bit.isset(lo, d6) and 1 or 0, 2),
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bit.lshift(bit.isset(lo, d7) and 1 or 0, 3),
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bit.lshift(bit.isset(hi, d4) and 1 or 0, 4),
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bit.lshift(bit.isset(hi, d5) and 1 or 0, 5),
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bit.lshift(bit.isset(hi, d6) and 1 or 0, 6),
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bit.lshift(bit.isset(hi, d7) and 1 or 0, 7))
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end
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-- init sequence from datasheet (Figure 24)
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local function justsend(what)
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i2c.start(busid)
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i2c.address(busid, busad, i2c.TRANSMITTER)
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i2c.write(busid, bit.set(what, en))
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i2c.write(busid, what)
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i2c.stop(busid)
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end
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local three = bit.bor(bit.bit(d4), bit.bit(d5))
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justsend(three)
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tmr.delay(5)
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justsend(three)
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tmr.delay(1)
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justsend(three)
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tmr.delay(1)
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justsend(bit.bit(d5))
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-- we are now primed for the FUNCTIONSET command from the liquidcrystal ctor
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-- Return backend object
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return {
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fourbits = true,
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command = function (_, cmd)
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return send4bitI2C(cmd, false, false)
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end,
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busy = function(_)
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return bit.isset(send4bitI2C(0xff, false, true), 7)
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end,
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position = function(_)
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return bit.clear(send4bitI2C(0xff, false, true), 7)
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end,
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write = function(_, value)
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return send4bitI2C(value, true, false)
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end,
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read = function(_)
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return send4bitI2C(0xff, true, true)
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end,
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backlight = function(_, on)
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backlight = on
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send4bitI2C(0, false, false) -- No-op
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return on
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end,
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}
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end
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