diff options
Diffstat (limited to 'microwire.lua')
| -rw-r--r-- | microwire.lua | 20 |
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 |