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ob-uart – integrate UART communication into org documents

Overview

ob-uart is a wrapper around make-serial-process for org babel, providing integration of UART communication into org documents.

Purpose

ob-uart is useful for communication with devices that use a simple, command based interface over UART, such as is often the case in embedded development.

Using ob-uart allows using org-mode to test and document the interface, e.g.:

set_value_portb 3 1

OK

get_adc0_voltage

0.778

Installation

To use ob-uart, add the repository to your load path, load it and add it to org-babel-load-languages.

(add-to-list 'load-path "~/path/to/ob-uart/")
(org-babel-do-load-languages
 'org-babel-load-languages
 '((uart . t)))

Example

ob-uart can also be useful for tools like the Bus Pirate. The following example shows a temperature readout from an SHT21 humidity & temperature sensor.

  • set mode to I²C, 50 kHz 
    m 4 2
    
    m 4 2
I2C (mod spd)=( 0 1 )
Ready
I2C>
  • enable power supply and pull-up resistors 
    WP
    
    WP
Power supplies ON
Pull-up resistors ON
I2C>
  • scan for devices 
    (1)
    
    (1)
Searching I2C address space. Found devices at:
0x80(0x40 W) 0x81(0x40 R)

    :

    I2C>
  • send command to trigger temperature measurement 
    [0x80 0b11110011 %]
    
    [0x80 0b11110011 %]
I2C START BIT
WRITE: 0x80 ACK
WRITE: 0xF3 ACK
DELAY 1ms
I2C STOP BIT
I2C>
  • get result data 
    [0x81 r:3]

    #+RESULTS[43d384c278126101882a82423eae8f83e4e43d62]: sht21_data

    [0x81 r:3]
I2C START BIT
WRITE: 0x81 ACK
READ: 0x64  ACK 0x74  ACK 0xEA
NACK
I2C STOP BIT
I2C>
  • calculate temperature 
    bytes = [int(x, 16) for x in data.split("\n")[3][5:].split(" ACK ")]
print("%.1f" % (-46.85 + 175.72 * (bytes[0] * 256 + bytes[1]) / 2**16))
    
    22.1