renaming LE pin and using GPIO15/CS for it

1 files changed, 12 insertions, 8 deletions

diff --git a/microwire.lua b/microwire.lua
index e2b5654..1fc87b4 100644
--- a/microwire.lua
+++ b/microwire.lua
@@ -4,7 +4,6 @@
 
 -- 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
@@ -14,11 +13,10 @@ databits=24
 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)
+-- we will use SPI ChipSelect pin for LoadEnable pin
+microwire_LE_pin = 8; -- microwire Load Enable pin. 8 --> GPIO15
 
+function microwire_setup_interface ()
 	-- 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
@@ -31,6 +29,12 @@ function microwire_setup_interface ()
 	-- HSPI /CS  | 8        | GPIO15
 	-- HSPI MOSI | 7        | GPIO13
 	-- HSPI MISO | 6        | GPIO12
+	
+	-- Load Enable pin settings
+	-- note that it overwrite unused ChipSelect if pin=8, i.e. GPIO15
+	gpio.mode(microwire_LE_pin, gpio.OUTPUT)
+	gpio.write(microwire_LE_pin, gpio.LOW)
+
 end
 
 function microwire_send_data( data )
@@ -38,13 +42,13 @@ function microwire_send_data( data )
 	-- and raise Load Enable pin for a bit (at least for25 nS) at the end of transmission
 	
 	-- first low LE pin
-	gpio.write(microwire_sle, gpio.LOW)
+	gpio.write(microwire_LE_pin, 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)
+	gpio.write(microwire_LE_pin, gpio.HIGH)
 	-- but since optocoupler is limiting us we will do it for longer
 	local microwireLEonTime = 100; -- time is in uS
 
@@ -53,7 +57,7 @@ function microwire_send_data( data )
 	-- so we use timer but unfortunately the smallest time is 1ms
 	microwireLEonTime = 1; -- time is in mS for timers
 	microwire_tmr = tmr.create()
-	microwire_tmr:register(microwireLEonTime, tmr.ALARM_SINGLE, function() gpio.write(microwire_sle, gpio.LOW) end)
+	microwire_tmr:register(microwireLEonTime, tmr.ALARM_SINGLE, function() gpio.write(microwire_LE_pin, gpio.LOW) end)
 	microwire_tmr:start()
 end