diff options
| -rw-r--r-- | microwire.lua | 19 |
1 files changed, 9 insertions, 10 deletions
diff --git a/microwire.lua b/microwire.lua index cc98a68..d6c1ff4 100644 --- a/microwire.lua +++ b/microwire.lua @@ -1,28 +1,27 @@ -- functions to write registers over microwire interface --- it resembles SPI but need exrta pin which sends Load Enable (LE) pulse --- otherwise SPI sequence is sent into 24 bit FIFO buffer +-- it resembles SPI but need extra pin which sends Load Enable (LE) pulse +-- otherwise SPI sequence is sent into 24 bit FIFO latch register on chip -- Pins assignment -- SPI Id selects which pins are used for CLK, MOSI, MISO, CS -spiID = 1; -- ID=1 --> HSPI in nodemcu language -databits=24; -- LMX2487 loads 24 bits sequence per write into a register --- default SPI clock is 80 MHz -fSPI = 80000000 +microwire_spiID = 1; -- ID=1 --> HSPI in nodemcu language +microwire_databits=24; -- LMX2487 loads 24 bits sequence per write into a register -- lmx2487 can handle up to 20 MHz speed (50 nS per clock) but optocoupler is good for 240kHz -- so let's aim for 100 kHz -maxMicrowireInterfaceSpeed = 100000; -- in Hz -clock_divider = math.floor(fSPI/maxMicrowireInterfaceSpeed) +microwire_interface_speed = 100000; -- in Hz -- we will use SPI ChipSelect pin for LoadEnable pin microwire_LE_pin = 8; -- microwire Load Enable pin. 8 --> GPIO15 function microwire_setup_interface () + local fSPI = 80000000; -- default SPI clock is 80 MHz + local clock_divider = math.floor(fSPI/microwire_interface_speed) -- 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.setup(microwire_spiID, spi.MASTER, spi.CPOL_LOW, spi.CPHA_LOW, microwire_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 @@ -45,7 +44,7 @@ function microwire_send_data( data ) gpio.write(microwire_LE_pin, gpio.LOW) -- second send the data - local nBytes = spi.send(spiID, data) + local nBytes = spi.send(microwire_spiID, data) -- finally raise LE pin for at least 25 ns, |