Differences

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--- projects:esp [2015/02/04 18:16]
darron [24LC512]
+++ projects:esp [2017/01/12 22:44]
@@ Line 1: / Line 1: @@
-==== Extrasensory perception for ESP-01 & RPi ====
-<wrap right>
-{{:projects:espwip.jpg?200|RPi B+}}
-\\ \\
-{{:projects:espi2c.jpg?200|ESP-01}}
-</wrap>
-This project adds three I2C devices to an [[:boards:esp8266|ESP-01]] or a [[:boards:rpi|Raspberry Pi]].
-The three devices are a Microchip MCP23016 digital I/O expander, NXP PCF8591 ADC/DAC and Microchip 24LC512 EEPROM.
-These were chosen because they add useful capabilities to the ESP-01 or RPi and all three are available in DIP format from CPC in the United Kingdom.
-=== Schematic ===
-{{:projects:esp.png?200}}
-=== I2C bus ===
-^Address ^Device |
-|0x20    |MCP23016|
-|0x48    |PCF8591|
-|0x50    |24LC512|
-Probing the bus on the RPi with [[:tools:i2ctools|I2C Tools]] should reveal the following.
-<code>
-i2cdetect -y 1
-  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
-:          -- -- -- -- -- -- -- -- -- -- -- -- --
-: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
-: 20 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
-: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
-: -- -- -- -- -- -- -- -- 48 -- -- -- -- -- -- --
-: 50 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
-: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
-: -- -- -- -- -- -- -- --
-</code>
-=== MCP23016 ===
-^Control ^Register ^Function |
-|0       |GP0|     GPO input |
-|1       |GP1|     GP1 input |
-|2       |OLAT0|   GP0 output |
-|3       |OLAT1|   GP1 output |
-|6       |IODIR0|  GP0 direction |
-|7       |IODIR1|  GP1 direction |
-To use the MCP23016 first set the GPIO direction register. Microchip use 1 for input and 0 for output. After that you can either read the input register or write to the output register.
-== ESP-01 NodeMcu ==
-First we need eSPY, fetch and build it. The examples below come with the source.
-<code>
-hg clone http://hg.kewl.org/pub/espy
-cd epsy
-make
-</code>
-This example script blinks an LED attached to the MCP23016 GP0.0 pin.
-<code>
-#!espy /dev/ttyUSB0
--- pin 3 = GPIO0
-sda=3
--- pin 4 = GPIO2
-scl=4
--- init I2C
-i2c.setup(0,sda,scl,i2c.SLOW)
--- write MCP
-function write_mcp(control,value)
-        i2c.start(0)
-        i2c.address(0,0x20,i2c.TRANSMITTER)
-        i2c.write(0,control)
-        i2c.write(0,value)
-        i2c.stop(0)
-end
--- init GP0.0
-write_mcp(2,0)
-write_mcp(6,0xFE)
--- blink LED on GP0.0 3 times
-for i = 1, 3, 1 do
-        write_mcp(2,1)
-        print ("on")
-        tmr.delay(1000000)
-        write_mcp(2,0)
-        print ("off")
-        tmr.delay(1000000)
-end
-</code>
-The script comes with the eSPY application and can be demomstrated thus.
-<code>
-./mcp.esp
-off
-on
-off
-on
-off
-</code>
-== RPi ==
-[[:tools:i2ctools|I2C Tools]] on the RPi are used to demonstrate the MCP23016 GPIO.
-Here we clear the output latch, set GP0.0 to an output, then set the pin high on the RPi.
-<code>
-i2cset -y 1 0x20 2 0
-i2cset -y 1 0x20 6 0xFE
-i2cset -y 1 0x20 2 1
-</code>
-Now on the RPi we set GP1.0 as an input then read it twice. The first read is with GP1.0 taken
-low and the second read with GP1.0 taken high.
-<code>
-i2cset -y 1 0x20 7 1
-i2cget -y 1 0x20 1
-xde
-i2cget -y 1 0x20 1
-xdf
-</code>
-Please refer to the [[#resources|data-sheet]] for full information for this part.
-=== PCF8591 ===
-^Control ^Register   ^Function |
-|0        | channel 0 |Read ADC 0|
-|1        | channel 1 |Read ADC 1|
-|2        | channel 2 |Read ADC 2|
-|3        | channel 3 |Read ADC 3|
-|+64      | analog OE |DAC output|
-To write to the DAC, we set the control to 64 and write a value between 0 and 255 which represents 0 to VREF volts on the output pin.
-To read from an ADC, we first send a control representing the channel, then we perform two reads. The first read starts the conversion process and the second read fetches the result (this also starts another conversion).
-If we are using the DAC, then we must also set the analog OE bit else the DAC will be disabled.
-== ESP-01 NodeMcu ==
-A simple ramp demo can be achieved like this with NodeMcu on the ESP-01.
-<code>
-#!espy /dev/ttyUSB0
--- pin 3 = GPIO0
-sda=3
--- pin 4 = GPIO2
-scl=4
--- init I2C
-i2c.setup(0,sda,scl,i2c.SLOW)
--- write DAC
-function write_dac(control,value)
-        i2c.start(0)
-        i2c.address(0,0x48,i2c.TRANSMITTER)
-        i2c.write(0,control)
-        i2c.write(0,value)
-        i2c.stop(0)
-end
--- DAC output
-for i = 0, 255, 10 do
-        write_dac(64,i)
-        print (i)
-        tmr.delay(100000)
-end
-</code>
-When the script is run with eSPY we can see the DAC output ramp up and a running commentary.
-<code>
-...
-</code>
-== RPi ==
-Using [[:tools:i2ctools|I2C Tools]] on the RPi we reset the output to 0V, then raise it to 1.6V and finally 3.3V.
-<code>
-i2cset -y 1 0x48 64 0
-i2cset -y 1 0x48 64 128
-i2cset -y 1 0x48 64 255
-</code>
-With a potentiometer connected to AIN0 a reading was made on the RPi.
-<code>
-i2cset -y 1 0x48 64 ; i2cget -y 1 0x48 ; i2cget -y 1 0x48
-x1b
-x8d
-</code>
-The second value above is the new reading, the first is the previous reading.
-This is simplified view of the operation of this device. Please read the [[#resources|data-sheet]] for the full details.
-=== 24LC512 ===
-I2C EEPROMs have varied addressing schemes. The simplest is a 8-bit address offset, another one where a block selection is made with an I2C address and a byte selection is made with an 8-bit address offset. Yet another, where the I2C address is fixed but it now has a 16-bit address offset and lastly one with both of the last methods combined.
-The 24LC512 which uses 16-bit addressing. The addressing byte order is high byte, low byte.
-== ESP-01 NodeMcu ==
-On the ESP-01 we can use this NodeMcu LUA script to read the EEPROM.
-<code>
-#!espy /dev/ttyUSB0
--- pin 3 = GPIO0
-sda=3
--- pin 4 = GPIO2
-scl=4
--- init I2C
-i2c.setup(0,sda,scl,i2c.SLOW)
--- read EEPROM
-function read_eeprom(addrhigh,addrlow)
-        i2c.start(0)
-        i2c.address(0,0x50,i2c.TRANSMITTER)
-        i2c.write(0,addrhigh)
-        i2c.write(0,addrlow)
-        i2c.stop(0)
-        i2c.start(0)
-        i2c.address(0,0x50,i2c.RECEIVER)
-        c=i2c.read(0,1)
-        i2c.stop(0)
-        return c
-end
--- read byte
-reg = read_eeprom(0x00,0x00)
--- output byte
-print(string.byte(reg))
-</code>
-Here the script is executed using eSPY.
-<code>
-./eeprom.esp
-</code>
-eSPY is still being developed and as yet doesn't filter the LUA prompts from the output.
-== RPi ==
-On the RPi we can reset the internal address pointer of the chip to 0 like this.
-<code>
-i2cset -y 1 0x50 0 0
-</code>
-To read, we first write an address to start at then begin reading, if we keep reading the address is auto-incremented.
-<code>
-i2cset -y 1 0x50 0 0
-i2cget -y 1 0x50
-x55
-i2cget -y 1 0x50
-xaa
-</code>
-If we want to write to a location we send the address followed by the byte of data.
-<code>
-i2cset -y 1 0x50 0 0 0xEE i
-i2cset -y 1 0x50 0 0
-i2cget -y 1 0x50
-xee
-</code>
-This overview gives enough information to use the device at a byte level, read the [[#resources|data-sheet]] for the page writing mode of operation.
-=== Resources ===
-[[http://ww1.microchip.com/downloads/en/DeviceDoc/20090C.pdf|MCP23016 data-sheet]]\\
-[[http://www.nxp.com/documents/data_sheet/PCF8591.pdf|PCF8591 data-sheet]]\\
-[[http://ww1.microchip.com/downloads/en/DeviceDoc/21754M.pdf|24LC512 data-sheet]]\\

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