microwire interface

1 files changed, 50 insertions, 6 deletions

diff --git a/microwire.lua b/microwire.lua
index e177731..993a8b5 100644
--- a/microwire.lua
+++ b/microwire.lua
@@ -2,13 +2,57 @@
 -- it resembles SPI but need exrta pin which sends Load Enable (LE) pulse
 -- otherwise SPI sequence is sent into 24 bit FIFO buffer 
 
-function setup_interface ()
-	-- Pins assignment
-	local sda = TBA; -- microwire DATA pin
-	local scl = TBA; -- microwire Clock (CLK) pin
-	local sle = TBA; -- microwire Load Enable pin
+-- Pins assignment
+-- SPI Id selects which pins are used for CLK, MOSI, MISO, CS
+microwire_sle = 4; -- microwire Load Enable pin. 2 --> GPIO2
+-- lmx2487 can hadle up to 20 MHz but optocoupler is good for 240kHz
+-- so let's aim to 100 kHz
+maxMicrowireInterfaceSpeed = 100000; -- in Hz
+spiID = 1; -- HSPI in nodemcu language
+databits=24
+-- default SPI clock is 80 MHz
+fSPI = 80000000
+clock_divider = math.floor(fSPI/maxMicrowireInterfaceSpeed)
+
+function microwire_setup_interface ()
+	-- Load Enable pin settings
+	gpio.mode(microwire_sle, gpio.OUTPUT)
+	gpio.write(microwire_sle, gpio.LOW)
+
+	-- now microwire <--> SPI setup
+	-- microwire is SPI with CPOL=0 and CPHA=0 i.e. SPI mode 0 = 00 = CPOL.CPHA
+	-- see https://en.wikipedia.org/wiki/Serial_Peripheral_Interface#Mode_numbers
+	-- see https://www.totalphase.com/support/articles/200348506-Using-the-Aardvark-adapter-with-a-Microwire-device
+	-- we are setting SPI Id = 1, since Id = 0 used for communication with memory
+	spi.setup(spiID, spi.MASTER, spi.CPOL_LOW, spi.CPHA_LOW, databits, clock_divider)
+	-- SPI Id=1 uses following pins https://nodemcu.readthedocs.io/en/master/modules/spi
+	-- Signal    | IO index | ESP8266 pin
+	-- HSPI CLK  | 5        | GPIO14
+	-- HSPI /CS  | 8        | GPIO15
+	-- HSPI MOSI | 7        | GPIO13
+	-- HSPI MISO | 6        | GPIO12
 end
 
-function microwire_write_data( data )
+function microwire_send_data( data )
+	-- essentially send data via spi interface and raise Load Enable
+	-- first low LE pin
+	gpio.write(microwire_sle, gpio.LOW)
+	-- second send the data
+	local nBytes = spi.send(spiID, data)
+	-- finally raise LE pin for at least 25 ns,
+	
+	gpio.write(microwire_sle, gpio.HIGH)
+	-- but since optocoupler is limiting us we will do it for longer
+	local microwireLEonTime = 100; -- in uS
+
+	-- the easiest to use tmr.delay( timeIn_uS ) but this halts everything
+	-- tmr.delay( microwireLEonTime )
+	-- so we use timer but unfortunately the smallest time is 1ms
+	microwireLEonTime = 1; -- now time is in mS
+	microwire_tmr = tmr.create()
+	microwire_tmr:register(microwireLEonTime, tmr.ALARM_SINGLE, function() gpio.write(microwire_sle, gpio.LOW) end)
+	microwire_tmr:start()
 end
 
+microwire_setup_interface()
+