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