Decoding UART protocol (from file)

Description

This example demonstrates how to decode the UART protocol using logic analyser commands. Red Pitaya loads the UART data from the “uart_data.bin” file and decodes it. When configuring the example, make sure that the UART decoder settings match the capture settings.

Here are the possible values for the decoder:

baudrate - 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200, 230400, 460800, 921600
bit order - LSB_FIRST = 0, MSB_FIRST = 1
invert - 0, 1 (invert input data signal)
number of data bits - 5, 6, 7, 8, 9
number of stop bits - STOP_BITS_NO = 0, STOP_BITS_05 = 1, STOP_BITS_10 = 2, STOP_BITS_15 = 3, STOP_BITS_20 = 4
parity - NONE = 0, EVEN = 1, ODD = 2, ALWAYS_0 = 3, ALWAYS_1 = 4
decoder lines - 1 - 8 (1 == DIO0_P)
trigger channel - LA_T_CHANNEL_1 - LA_T_CHANNEL_8 (1 == DIO0_P)

The possible decoded data packet types are:

Parity bit error - the parity bit of the UART message is not detected (control value 0)
Start bit error - the start bit of the UART message is not detected (control value 1)
Stop bit error - the stop bit of the UART message is not detected (control value 2)
Data - the data bits of the UART message (control value 3)
Start bit - the start bit of the UART message (control value 4)
Stop ok - the stop bit of the UART message (control value 5)
Parity bit - the parity bit of the UART message (control value 6)

Each packet has the following parameters:

control - Data identifier.
data - Data contained in the protocol.
line name - Line name according to the protocol for which the data was decoded. Must be specified in the decoder settings, otherwise they will not be present.
sampleStart - Starting position in the data to be recognized in samples. 0 = first sample, 1 = second sample, etc. The value is not an integer, since the bit width can be real depending on the protocol. Includes the pretrigger samples.
length - Length of the recognized block in samples.

\[\text{l_{packet}} = \frac{125~\mathrm{MHz}}{\text{decimation} \cdot \text{uart_baudrate}} \cdot \text{bitsInPack}\]
bitsInPack - Number of recognized data bits. Multiple of 0.5.

Required hardware

Red Pitaya

Required software

IN DEV - Nightly Build OS

Note

This code is written for IN DEV and will not work with the currently available OS releases. To use this functionality, please install the Nightly Build OS versions.

API Code Examples

Code - Python

#!/usr/bin/python3
""" Example for decoding LA UART data from file. Settings are also loaded from a file.
"""
import rp_la

rp_cla = rp_la.CLAController()

rp_cla.loadFromFile("uart_data.bin", True, 0)

rp_cla.addDecoder("UART", rp_la.LA_DECODER_UART)
f = open("uart_settings.json", "r", encoding='utf8')
rp_cla.setDecoderSettings("UART", f.read())

print("Settings:")
print(rp_cla.getDecoderSettings("UART"))

print("\nDecoded data\n")
decode = rp_cla.decode("UART")
for index in range(len(decode)):
    print(rp_cla.getAnnotation(rp_la.LA_DECODER_UART,decode[index]['control'])," = ",decode[index])
del rp_cla

Modifying decoder settings

#!/usr/bin/python3
"""This script demonstrates how to modify the settings of the UART decoder in the json files."""

import json
import rp_hw_profiles
import rp_la

# Define callback
class Callback(rp_la.CLACallback):
    def captureStatus(self, controller, isTimeout, bytes, samples, preTrig, postTrig):
        print("captureStatus timeout =",isTimeout,"bytes =",bytes,"samples =",samples,"preTrig =",preTrig,"postTrig =",postTrig)

    def decodeDone(self, controller, name):
        print("Decode done ",name)

uart_decoder = "UART"

decimation = 16
acq_rate = int(rp_hw_profiles.rp_HPGetBaseSpeedHzOrDefault() / decimation)

# Create controller
rp_cla = rp_la.CLAController()

callback = Callback()
rp_cla.setDelegate(callback.__disown__())

# LA FPGA must be loaded/LA Application must be open
rp_cla.initFpga()

# Add decoders
rp_cla.addDecoder(uart_decoder, rp_la.LA_DECODER_UART)

# Get settings from Red Pitaya
uart_settings = rp_cla.getDecoderSettings(uart_decoder)
print(f"UART decoder settings: {uart_settings}")

# Modify settings
uart_settings = json.loads(uart_settings)

uart_settings["acq_speed"    ] = acq_rate   # Acquisition speed =! decimation setting
uart_settings["baudrate"     ] = 921600     # 1200,2400,4800,9600,19200,38400,57600,115200,230400,576000,921600
uart_settings["bitOrder"     ] = 0          # LSB_FIRST = 0, MSB_FIRST = 1
uart_settings["invert"       ] = 0
uart_settings["num_data_bits"] = 8          # 5, 6, 7, 8, 9
uart_settings["num_stop_bits"] = 1          # 0 = 0, 0.5 = 1, 1.0 = 2, 1.5 = 3, 2.0 = 4
uart_settings["parity"       ] = 2          # NONE = 0, EVEN = 1, ODD = 2, ALWAYS_0 = 3, ALWAYS_1 = 4
uart_settings["rx"           ] = 1          # UART RX   (1 - first line.  Valid values are from 1 to 8), 0 == disabled
uart_settings["tx"           ] = 0          # UART TX

# Save json data to a file
with open("uart_settings.json", "w", encoding='utf8') as json_file:
    json.dump(uart_settings, json_file, indent=4)

del rp_cla

Save decoder settings to a json file

#!/usr/bin/python3
"""This script demonstrates how to save the settings of the UART decoder to a json file."""

import json
import rp_la

# Define callback
class Callback(rp_la.CLACallback):
    def captureStatus(self, controller, isTimeout, bytes, samples, preTrig, postTrig):
        print("captureStatus timeout =",isTimeout,"bytes =",bytes,"samples =",samples,"preTrig =",preTrig,"postTrig =",postTrig)

    def decodeDone(self, controller, name):
        print("Decode done ",name)

# Create controller
rp_cla = rp_la.CLAController()
callback = Callback()
rp_cla.setDelegate(callback.__disown__())

# LA FPGA must be loaded/LA Application must be open
rp_cla.initFpga()

# Add decoders
rp_cla.addDecoder("UART", rp_la.LA_DECODER_UART)

# Get settings from Red Pitaya
uart_settings = rp_cla.getDecoderSettings("UART")

print(f"UART decoder settings: {uart_settings}")

# Save json data to a file
uart_settings = json.loads(uart_settings)
with open("uart_settings.json", "w", encoding='utf8') as json_file:
    json.dump(uart_settings, json_file, indent=4)

del rp_cla