tests: NTest gpio

Use the hardware defined in the test environment to exercise some gpio
pins and trigger logic.

tests/NTest_gpio_env.lua

@@ -0,0 +1,88 @@
+-- Walk the GPIO subsystem through its paces, using the attached I2C GPIO chip
+--
+--   Node GPIO 13 (index 7) is connected to I2C expander channel B6; node OUT
+--   Node GPIO 15 (index 8) is connected to I2C expander channel B7; node IN
+
+local N = require('NTest')("gpio-env")
+
+-- TODO: Preflight test that we are in the correct environment with an I2C
+-- expander in the right place with the right connections.
+
+-- TODO: Use the mcp23017 module in the main tree rather than hand-coding
+-- the commands
+
+N.test('setup', function()
+  -- Set gpio pin directions
+  gpio.mode(8, gpio.INPUT)
+  gpio.mode(7, gpio.OUTPUT, gpio.FLOAT)
+
+  -- Configure the I2C bus
+  i2c.setup(0, 2, 1, i2c.FAST)
+
+  -- Set the IO expander port B to channel 7 as output, 6 as input
+  i2c.start(0)
+  ok(i2c.address(0, 0x20, i2c.TRANSMITTER))
+  i2c.write(0, 0x01, 0x7F)
+  i2c.stop(0)
+end)
+
+local function seti2cb7(v)
+  i2c.start(0)
+  i2c.address(0, 0x20, i2c.TRANSMITTER)
+  i2c.write(0, 0x15, v and 0x80 or 0x00)
+  i2c.stop(0)
+end
+
+local function geti2cb6()
+  i2c.start(0)
+  i2c.address(0, 0x20, i2c.TRANSMITTER)
+  i2c.write(0, 0x13)
+  i2c.start(0)
+  i2c.address(0, 0x20, i2c.RECEIVER)
+  local v = i2c.read(0, 1):byte(1)
+  i2c.stop(0)
+  return (bit.band(v,0x40) ~= 0)
+end
+
+N.test('gpio read 0', function()
+  seti2cb7(false)
+  ok(eq(0, gpio.read(8)))
+end)
+
+N.test('gpio read 1', function()
+  seti2cb7(true)
+  ok(eq(1, gpio.read(8)))
+end)
+
+N.test('i2c read 0', function()
+  gpio.write(7, 0)
+  ok(eq(false, geti2cb6()))
+end)
+
+N.test('i2c read 1', function()
+  gpio.write(7, 1)
+  ok(eq(true, geti2cb6()))
+end)
+
+N.testasync('gpio toggle trigger 1', function(next)
+  seti2cb7(false)
+  tmr.delay(10)
+  gpio.trig(8, "both", function(l,_,c)
+    ok(c == 1 and l == 1)
+    return next()
+  end)
+  seti2cb7(true)
+end, true)
+
+N.testasync('gpio toggle trigger 2', function(next)
+  gpio.trig(8, "both", function(l,_,c)
+    ok(c == 1 and l == 0)
+    return next()
+  end)
+  seti2cb7(false)
+end, true)
+
+N.test('gpio toggle trigger end', function()
+  gpio.trig(8, "none")
+  ok(true)
+end)