Bosch XDK110 Getting Started

XDK110: Getting Started Guide with Extension Bus

Cross-Domain Development Kit XDK110

Platform for Application Development

XDK110: Extension Bus Advanced Guide

Document revision

1.0

Document release date

11. May 2018

Workbench version

3.3.0 and above

Document number

BCDS-XDK110-GUIDE Extension Bus Advanced

Technical reference code(s)

Notes

Data in this document is subject to change without notice. Product photos and pictures are for illustration purposes only and may differ from the real product’s appearance. This document is conﬁdential and under NDA inherent with the purchase of an XDK110.

Advance information – Subject to change without notice

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Extension Bus Advanced Guide | XDK110

XDK110

Platform for Application Development

Table of contents

1. General Description 4

1.1 General Introduction 4.............................................................................................................................................

1.2 Connecting the Extension Bus 4.............................................................................................................................

1.3 MCU pins on the Extension Bus 4...........................................................................................................................

2. Extension Bus Advanced API Overview 6

2.1 Preparation 6...........................................................................................................................................................

3. UART (Universal Asynchronous Receiver-Transmitter) 7

3.1 General Introduction 7.............................................................................................................................................

Conﬁgurable parameters for UART are: 7.....................................................................................................................

3.2 Initializing and conﬁguring UART 8.........................................................................................................................

3.3 Transmitting data over UART 13.............................................................................................................................

3.4 Receiving data over UART 14.................................................................................................................................

4. SPI (serial peripheral interface bus) 15

4.1 General Introduction 15...........................................................................................................................................

4.2 Initializing and conﬁguring SPI 15...........................................................................................................................

4.3 Transmitting data over SPI 20.................................................................................................................................

4.4 Receiving data over SPI 22.....................................................................................................................................

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Extension Bus Advanced Guide | XDK110

This guide postulates a basic understanding of the XDK and the according workspace. For new users we recommend going through the following guides at xdk.io/guides ﬁrst:

Workbench Installation

Workbench First Steps

XDK Guide FreeRTOS!

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Extension Bus Advanced Guide | XDK110

1. General Description

1.1 General Introduction

The XDK comes with the ability to attach a 26 pin XDK gateway called extension bus to its own 26 pin connector. The extension bus allows over the 26 additional pins access to pin functionality of the XDKs MCU pins by attaching external devices such as sensors or actuators to it. All MCU pins are GPIOs and can be conﬁgured freely within the limitations of the MCU. This way, developers can use the hardware and software of XDK to test new components with minimal application effort.

The availability and the names of the different MCU pins will be explained in section 1.3. For further information on the MCU pin functionality, please refer to the MCU data sheet(LINK).

Other than the basic Extension Bus guide, the Extension Bus Advanced guide will focus on the three most common serial bus protocols UART, SPI and I2C, all of which are mature, industry standard technologies.

1.2 Connecting the Extension Bus

Connect the 26-pin cable (included in delivery) to the extension bus board and to the 26-pin connector of the XDK. The extension bus offers a simple way to implement additional functions with external components. It is optimized for the use with breadboards.

1.3 MCU pins on the Extension Bus

The extension bus I/O pins are labeled with the respective MCU pin designator. The following table is an excerpt of the available pins on the extension bus. It only contains the pins used for the serial bus protocols used in this guide. For the complete table please refer to the basic Extension Bus guide.

Table 1. Pin labelling and conﬁguration of the extension bus

Please note that the pins B9 and B10 are internally modiﬁed to suit the standards set for I2C pins. These pins are equipped with an internal pull-up resistor of 3.32 kOhm and are therefore usable for I2C communication only."

CONNECTOR

MCU

SUGGESTED USE

MULTIPLEX

LOCATION

MACRO

PB9

UART1 TX

UART1 #2

EXTENSION_UART1_TX

PB10

UART1 RX

UART1 #2

EXTENSION_UART1_RX

PB2

UART1 RTS

n/a

EXTENSION_UART1_RTS

PF6

UART1 CTS

n/a

EXTENSION_UART1_CTS

PB4

SPI MISO

USART2 #1

EXTENSION_US2_MISO

PB3

SPI MOSI

USART2 #1

EXTENSION_US2_MOSI

PB5

SPI Clock

USART2 #1

EXTENSION_US2_SCK

PD8

SPI Chip select

n/a

EXTENSION_US2_CS

PB11

I2C1 data line ! (pull-up)

I2C1 #1

EXTENSION_I2C1_SDA

B10

PB12

I2C1 clock line! (pull-up)

I2C1 #1

EXTENSION_I2C1_SCL

B13

GND

Power

n/a

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Extension Bus Advanced Guide | XDK110

Additionally, please note that the pins of the extension bus are protected against electrostatic discharge (ESD) up to 4 kV. This includes a serial resistance of 40 Ohm into the signal path. Please note that this is no problem for communication, but it need to be considered when powering external components via GPIO, e.g. an LED.

Keep those limitations of the Extension Bus gateway in mind when interacting with the UART, SPI and I2C pins. For further information about the general characteristics and limitations, please refer to the basic Extension Bus guide.

Before you start to connect external components to the XDK, please note the following limitations.

The pin voltage of every general purpose extension bus pin is 2.5 V. If you connect external components that work on a different voltage level, a level shifter has to be used to ensure communication with the MCU.

Failing to do so can lead to permanent damage of the XDK!

The micro controller supports four general purpose pin current drive strength settings: 0.5, 2,6 and 20 mA. The default drive strength is set to 6 mA and an alternative level can be deﬁned for each port. For how to conﬁgure these current drive strengths, please refer to chapter 1.X in the Extension Bus Basis guide. While each pin can receive or provide maximum 20 mA current, there is a limit on the maximum combined current sourced or sank by all GPIOs. As the XDK board itself has many useful peripherals connected to the MCU, which may require speciﬁc alternative drive strength settings if enabled, it is recommended to use the default 6 mA drive strength for all I/O pins of the extension board connector and to limit the total amount of current sourced or sank through the extension board bus to 50 mA. Exceeding

these limits might permanently damage the micro controller!"

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Extension Bus Advanced Guide | XDK110

2. Extension Bus Advanced API Overview

It is generally recommended to develop an application based on the highest API level the XDK framework supports, although it is possible to access deeper API levels if the highest level does not provide the functionality required for a speciﬁc purpose.

As with most XDK functionalities, there is an API allowing simple access to necessary functions for developing applications that use the serial bus protocols on the Extension Bus. For that the BSP and Utils API provided by the Platform layer will be used.

Picture 1 illustrates the interfaces for UART, SPI and I2C from the corresponding API.

Picture 1. API Overview

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2.1 Preparation

The application in this guide is based on an empty XdkApplicationTemplate project, which can be opened from the Welcome-screen of the XDK-Workbench. The code snippets should be placed into appInitSystem() one after another. It is recommended to create a new project for every chapter (UART, SPI, I2C), based on an empty XdkApplicationTemplate.

UARTTransceiver

freeRTOS

XDK Application

EmLib

XDK Extension Bus API

SPI

UART

ExtensionPort

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Extension Bus Advanced Guide | XDK110

3. UART (Universal Asynchronous Receiver-Transmitter)

3.1 General Introduction

UART stands short for Universal Asynchronous Receiver Transmitter and it is a physical circuit in a micro controller or a stand-alone IC. A UART’s main purpose is to transmit and receive serial data over two wires. In UART communication, two#UARTs communicate directly with each other.

UARTs transmit data asynchronously, which# means there is no clock signal to synchronize the output of bits from the transmitting UART to the sampling# of bits by the receiving UART. Instead of a clock signal, the transmitting UART adds start and stop bits to the data packet being transferred. These bits deﬁne the beginning and end of the data packet so the receiving UART knows when to start reading the bits.

Data transmitted via UART is organized into packets. Each#packet contains#1 start bit, 5 to 9 data bits (depending on the UART hardware interface), an optional parity bit, and#1 or 2 stop bits:

Picture 2. UART Packet Frame

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The data rate for UART range from 230.4kbps to 16Mbps.

Conﬁgurable parameters for UART are:

• Baud rate: The Baud rate is a measure of the speed of data transfer at which data can be transferred and incoming data

is read. It is expressed in bits per second (bps).

• Start Bit: The ﬁrst bit of an ongoing UART data packet transmission. It indicates that the data line is leaving its idle state,

typically from logic high to logic low. It simpliﬁes communication between transmitter and receiver, but does not deliver meaningful data.

• Stop Bit: The last bit of an ongoing UART data packet transmission represents the end of the data transmission. It

raises the logic level back into the idle state, typically to logic high.$

• Parity bit: Parity describes the evenness or oddness of a number. The parity bit is a way for#the receiving UART to tell if

any data has#changed during transmission. After the receiving UART reads the data frame, it counts the number of bits with a value of 1 and checks if the total#is an even or odd number.#If the parity bit is a 0 (even parity), the bits in the data frame should total to an even number. If the parity bit is a 1 (odd parity), the 1 bits in the data frame should total to an odd number. When# the parity bit matches the data, the UART knows that the transmission was free of error. But if the parity bit is a 0, and the total is odd or the parity bit is a 1, and the total is even, the UART knows that bits in the data frame have changed.

Please note that for a working UART communication it is necessary that both UART endpoints operate at the same baud rate. Furthermore, the same conﬁguration about the start, stop and parity bits need to be applied to both endpoints.

UART Packet

1 start bit

5 to 9 data bits

0 to 1 parity bits

1 to 2 stop bits

Data Frame

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Extension Bus Advanced Guide | XDK110

3.2 Initializing and conﬁguring UART

This section describes how to initialize UART either to receive or transmit data. It also covers the necessary conﬁguration for the baud rate, the start bit, stop bit and parity bit. For that, the following interfaces will be used.

Code 1. Including the required UART interfaces

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The BSP_ExtensionPort.h is used to connect and conﬁgure the UART interface on the Extension Bus. With it, the conﬁguration of the Baud rate, the start, stop and parity bits will be implemented.

The following Table shows an excerpt of the functions used to implement a working UART connection.

Table 2. Function overview BSP_ExtensionPort.h

The interface BCDS_MCU_UART.h is used to initialize UART on the driver level to handle the events when data is received or transmitted via UART over the function MCU_UART_Initialize().

Furthermore, the interface BCDS_UARTTransceiver.h is used to extend UART to add functionality such as a ring buffer to store the incoming data and to send out data streams greater than one UART data packet. "

#include "BSP_ExtensionPort.h" #include "BCDS_MCU_UART.h" #include "BCDS_UARTTransceiver.h "

FUNCTION

DESCRIPTION

BSP_ExtensionPort_Connect()

This function is called to enable the power control for the extension bus and disables all GPIO pins to conserve power

BSP_ExtensionPort_ConnectUart()

This function is called to configure the corresponding UART receive (RX) and transmit (TX) pins on the extension bus

BSP_ExtensionPort_SetUartConfig()

This function is called to configure UART settings, such as Baud rate, start bit, stop bit and parity bit

BSP_ExtensionPort_GetUartHandle()

This function returns the handle for the UART communication holding all relevant configuration data

BSP_ExtensionPort_EnableUart()

This function is called to enable the UART module for transmitting and reading data

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