LiquidCrystal robustness and test (#3369)
* LiquidCrystal I2C 4-bit robustness - Fix up some formatting - Initialization is now more conformant with the datasheet. - Read-backs don't needlessly (or erroneously!) store back While here, document some unexpected behaviour of read-back commands. * liquidcrystal i2c 4bit NTest
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Nathaniel Wesley Filardo
GitHub
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@ -237,6 +237,12 @@ liquidcrystal:blink(true)
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## liquidcrystal.busy
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Get busy status of the LCD. When using GPIO backend without `rw` argument specification function does nothing.
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!!! note
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At least some HD44780s and/or interfaces have been observed to count polling
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the busy flag as grounds for incrementing their position in memory. This is
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mysterious, but software should restore the position after observing that the
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busy flag is clear.
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#### Syntax
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`liquidcrystal.busy(self)`
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@ -429,6 +435,11 @@ liquidcrystal:leftToRight()
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## liquidcrystal.position
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Get current position of the cursor. Position is 0 indexed. When using GPIO backend without `rw` argument specification function does nothing.
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!!! note
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At least some HD44780s and/or interfaces have been observed to count reading
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the position as grounds for incrementing their position in memory. This is
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mysterious, but software likely intends to restore the position anyway.
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#### Syntax
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`liquidcrystal.position(self)`
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@ -22,27 +22,27 @@ return function(bus_args)
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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 send4bitI2C(value, rs_en, rw_en, read)
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local function exchange(data, unset_read)
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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))
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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)
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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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if unset_read then data = bit.bor(bit.bit(rs),
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bit.bit(rw),
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backlight and bit.bit(bl) or 0) end
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i2c.write(busid, bit.set(data, en))
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end
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i2c.write(busid, bit.clear(data, en))
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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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@ -51,11 +51,8 @@ return function(bus_args)
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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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local cmd = 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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hi = exchange(bit.bor(cmd, hi), false)
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lo = exchange(bit.bor(cmd, lo), true)
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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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@ -66,36 +63,45 @@ return function(bus_args)
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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
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send4bitI2C(0x33, false, false, false)
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send4bitI2C(0x32, false, false, false)
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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, false)
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return send4bitI2C(cmd, false, false)
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end,
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busy = function(_)
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local rv = send4bitI2C(0xff, false, true, true)
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send4bitI2C(bit.bor(0x80, bit.clear(rv, 7)), false, false, false)
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return bit.isset(rv, 7)
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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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local rv = bit.clear(send4bitI2C(0xff, false, true, true), 7)
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send4bitI2C(bit.bor(0x80, rv), false, false, false)
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return rv
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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, false)
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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, true)
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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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local rv = bit.clear(send4bitI2C(0xff, false, true, true), 7)
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send4bitI2C(bit.bor(0x80, rv), false, false, false)
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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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@ -0,0 +1,83 @@
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-- Run LiquidCrystal through some basic tests. Requires `liquidcrystal.lua`
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-- and `l2-i2c4bit.lua` available available to `require`.
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--
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-- This file ought to be named "NTest_liquidcrystal_i2c4bit" or something,
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-- but it has its current name due to our default SPIFFS filename length limit.
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local N = ...
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N = (N or require "NTest")("liquidcrystal-i2c4bit")
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local metalcd
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local metaback
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local backend
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local lcd
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collectgarbage()
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print("HEAP init", node.heap())
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metalcd = require "liquidcrystal"
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collectgarbage() print("HEAP constructor imported ", node.heap())
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metaback = require "lc-i2c4bit"
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collectgarbage() print("HEAP backend imported ", node.heap())
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backend = metaback({
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address = 0x27,
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id = 0,
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speed = i2c.SLOW,
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sda = 2,
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scl = 1,
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})
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collectgarbage() print("HEAP backend built", node.heap())
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lcd = metalcd(backend, false, true, 20)
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collectgarbage() print("HEAP lcd built", node.heap())
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print("waiting for LCD to be unbusy before testing...")
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while lcd:busy() do end
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N.test("custom character", function()
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local glyph = { 0x1F, 0x15, 0x1B, 0x15, 0x1F, 0x10, 0x10, 0x0 }
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lcd:customChar(0, glyph)
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ok(eq(glyph,lcd:readCustom(0)), "read back")
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end)
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N.test("draw and readback", function()
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lcd:cursorMove(0)
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lcd:write("abc")
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lcd:cursorMove(10,1)
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lcd:write("de")
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lcd:cursorMove(10,2)
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lcd:write("fg")
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lcd:cursorMove(12,3)
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lcd:write("hi\000")
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lcd:cursorMove(18,4)
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lcd:write("jk")
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lcd:home() ok(eq(0x61, lcd:read()), "read back 'a'")
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ok(eq(0x62, lcd:read()), "read back 'b'")
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lcd:cursorMove(11,1) ok(eq(0x65, lcd:read()), "read back 'e'")
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lcd:cursorMove(11,2) ok(eq(0x67, lcd:read()), "read back 'g'")
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lcd:cursorMove(13,3) ok(eq(0x69, lcd:read()), "read back 'i'")
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lcd:cursorMove(14,3) ok(eq(0x00, lcd:read()), "read back 0" )
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lcd:cursorMove(19,4) ok(eq(0x6B, lcd:read()), "read back 'k'")
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end)
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N.test("update home", function()
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lcd:home() lcd:write("l")
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lcd:home() ok(eq(0x6C, lcd:read()))
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end)
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N.testasync("clear", function(next)
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-- clear and poll busy
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lcd:clear()
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tmr.create():alarm(5, tmr.ALARM_SEMI, function(tp)
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if lcd:busy() then tp:start() else next() end
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end)
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lcd:home() -- work around busy polling incrementing position (XXX)
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ok(eq(0x20, lcd:read()), "is space")
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ok(eq(1, lcd:position())) -- having just read 1 from home, we should be at 1
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end)
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