Pytronics

Pytronics is a Python library used to control the electronic hardware on the Rascal. It closely mirrors the library of functions used by the Arduino. This page describes the Pytronics functions available for use in response to web requests. If you need more detail, try looking at the Pytronics code itself.

Summary of useful URLs (coming in Cooties software release)##

The parts with angle brackets, like <analog pin>, mean "substitute a number in here."

The sections in braces, like { data: <data> } mean "pass JSON with your request that looks like this."

Name	Request	URL
analog read	GET	/analog/read/<analog pin>
analog write	POST	(can't actually do this with current Rascal kernel)
digital read	GET	/digital/read/<pin>
digital write	POST	/digital/write/<pin>, { data: <data> }
I²C read	GET	/i2c/read/<addr>/<reg>/<num_bytes>
I²C write	POST	/i2c/write/<addr>/<reg>, { data: <data> }
serial read	GET	/serial/read/<channel>/<speed>/<num_bytes>
serial write	POST	/serial/write/<channel>/<speed>, { data: <data> }
SPI read	GET	/spi/read/<channel>/<speed>/<num_bytes>
SPI write	POST	/spi/write/<channel>/<speed>, { data: <data> }

Other useful URLs (coming in Cooties software release)

Shortcuts

Name	Request	URL
digital toggle	GET or POST	/digital/toggle/<pin>
digital write shortcut	GET or POST	/digital/write/<pin>/<state>

BlinkM smart LED

Name	Request	URL
set hue, saturation and brightness	GET or POST	/blinkm/<address>/hsb/<hue>/<saturation>/<brightness>
get hue, saturation and brightness	GET or POST	/blinkm/<address>/hsb

4D Systems PICASO microLCDs

Name	Request	URL
clear LCD	GET or POST	/fd/clear-lcd
draw filled rectangle	GET or POST	/fd/draw-filled-rectangle/<x1>/<y1>/<x2>/<y2>/<color>

Rascal Micro precision voltage shield

Name	Request	URL
reset shield	GET or POST	/pvs/reset
read voltages	GET or POST	/pvs/read

Functions for reading data

digitalRead(pin)

The function digitalRead() reads the voltage on one of the Rascal's digital pins. If the voltage is below 0.8 V, digitalRead() returns 0. If the voltage is above 2.0 V, digitalRead() returns 1. (Note that a voltage above 3.6 V will probably damage the Rascal's pins.)

Parameters

pin String consisting of a pin name, like '2', '3', or 'LED'

Return type

Returns a string equal to either '0' or '1'.

analogRead(pin)

The function analogRead() reads the voltage on one of the Rascal's analog inputs, scaled by the voltage on the A/D REF pin. A voltage of 0 V maps to a reading of 0. A voltage equal to or above the voltage on the A/D REF pin maps to a reading of 1023. (Note that a voltage above 3.6 V will probably damage the Rascal's pins.) Voltages in between 0 and A/D REF are mapped linearly between 0 and 1023. As an example, if you connect A/D REF to 3.3 V, a voltage of 1.65 V will produce a reading halfway between 0 and 1023 (roughly 512).

Parameters

pin String consisting of an analog pin name, like 'A0', 'A1', 'A2', or 'A3'

Return type

Returns a string containing a number in the range 0-1023.

On error, returns "Not an analog pin. Try 'A0', 'A1', 'A2', or 'A3'."

i2cRead(addr, reg = 0, size = 'B')

The function i2cRead() reads one or more bytes from a device on the I²C bus.

Parameters

addr Chip address
reg Memory address on chip
size 'C', 'W', 'B' or None, representing type of read requested, character, word, block, or short

Return type

Returns data read from device

spiRead()

The function spiRead() is not implemented yet . . .

Parameters

chip

Return type

Returns data

Functions for sending data

digitalWrite(pin, state)

The function digitalWrite() sets the voltage on one Rascal pin to either 3.3 V or 0 V, depending on the value of state passed in.

Parameters

pin String consisting pin name
state 'HIGH' or 'LOW'

Return type

Returns None

i2cWrite(addr, reg, val = '', size = 'B')

The function i2cWrite() sends one or more bytes onto the I²C bus.

Parameters

addr Chip address
reg Memory address on chip
val Data to write
size 'C', 'W', 'B' or None, representing type of write requested, character, word, block, or short

Return type

Returns None

serialWrite(text, speed=19200, port='1')

The function serialWrite() is used to send data out the Rascal serial ports.

Parameters

text String consisting of characters to be sent. Truncated after 80 characters.
speed (optional) Integer. Defaults to 19200.
port (optional) String ('1', '2', or '3'). Defaults to '1'.

Return type

Returns None

spiWrite(data, channel='0')

The function spiWrite() sends data over one of the Rascal's four SPI channels. The maximum speed of the SPI port is limited in the kernel driver to 14.67 MHz, but can be decreased with an ioctl call that hasn't been sorted out yet.

Parameters

data Integer or string to be sent.
channel (optional) String representing SPI channel to use ('0', '1', '2', or '3'). Defaults to '0'.

Return type

Returns None