Redefine your SPI's signal level shifting experience with PIC18LF25K40
Seamless SPI signals logic level conversion
Published Nov 01, 2023
Click board™
LLC-SPI Click
Dev Board
EasyPIC v7a
Compiler
NECTO Studio
MCU
PIC18LF25K40
From concept to implementation, our SPI-signal logic level converter simplifies complex voltage conversion challenges, providing the precision, adaptability, and control you need to achieve exceptional results in your project
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Hardware Overview
How does it work?
LLC SPI Click does not use any integrated circuit, as already mentioned. With ICs avoided completely, there are some benefits gained: the overall cost of the LLC circuit is greatly reduced, a more robust MOSFET solution reduces the failure rate, and when powered off, both the low voltage and the high voltage sides are isolated from one another (by non-conductive MOSFETs). This type of circuit is sometimes referred to as a level shifting or level translating circuit and it is often necessary when one SPI device (typically a sensor IC) uses different logic voltage levels for the communication than the controller device, which
is a microcontroller (MCU) in most cases. The conversion of this circuitry is bi-directional, which makes it suitable to be used with the SPI communication protocol. The SPI protocol was first introduced by Motorola, in the '80s. The circuit is divided into low-side and high-side sections for future reference, however, both up-shifting, and down-shifting of the voltage level is possible. The mechanisms are slightly different, so each will be explained separately. The reference voltage for the high-side can be selected by using the SMD jumper labeled as VCC SEL. The pull-up voltage for the high-side can be selected from the
mikroBUS™ power rails, so it can be either 3.3V or 5V. For the low-side, an arbitrary reference voltage can be applied to the VSL pin of the J1 header, respecting the maximum voltage rating, as well as the condition mentioned above. J1 is the standard, 2.54mm pin-header. The low-side SPI related pins are also routed to the J1 header, allowing an external device to be connected (using the standard wire-jumpers). As already mentioned, the low-side can actually use higher voltage levels than the master, but in most usage scenarios, it will be lower than the master, thus the terminology used in the text above.
Features overview
Development board
EasyPIC v7a is the seventh generation of PIC development boards specially designed for the needs of rapid development of embedded applications. It supports a wide range of 8-bit PIC microcontrollers from Microchip and has a broad set of unique functions, such as the first-ever embedded debugger/programmer over USB-C. The development board is well organized and designed so that the end-user has all the necessary elements in one place, such as switches, buttons, indicators, connectors, and others. With four different connectors for each port, EasyPIC v7a allows you to connect accessory boards, sensors, and custom electronics more efficiently than ever. Each part of the EasyPIC v7a development board
contains the components necessary for the most efficient operation of the same board. In addition to the advanced integrated CODEGRIP programmer/debugger module, which offers many valuable programming/debugging options and seamless integration with the Mikroe software environment, the board also includes a clean and regulated power supply module for the development board. It can use various external power sources, including an external 12V power supply, 7-23V AC or 9-32V DC via DC connector/screw terminals, and a power source via the USB Type-C (USB-C) connector. Communication options such as USB-UART and RS-232 are also included, alongside the well-
established mikroBUS™ standard, three display options (7-segment, graphical, and character-based LCD), and several different DIP sockets. These sockets cover a wide range of 8-bit PIC MCUs, from PIC10F, PIC12F, PIC16F, PIC16Enh, PIC18F, PIC18FJ, and PIC18FK families. EasyPIC v7a is an integral part of the Mikroe ecosystem for rapid development. Natively supported by Mikroe software tools, it covers many aspects of prototyping and development thanks to a considerable number of different Click boards™ (over a thousand boards), the number of which is growing every day.
Microcontroller Overview
MCU Card / MCU
Architecture
PIC
MCU Memory (KB)
32
Silicon Vendor
Microchip
Pin count
28
RAM (Bytes)
2048
Used MCU Pins
mikroBUS™ mapper
Take a closer look
Schematic
Step by step
Project assembly
Start by selecting your development board and Click board™. Begin with the EasyPIC v7a as your development board.
Track your results in real time
Application Output
After pressing the "FLASH" button on the left-side panel, it is necessary to open the UART terminal to display the achieved results. By clicking on the Tools icon in the right-hand panel, multiple different functions are displayed, among which is the UART Terminal. Click on the offered "UART Terminal" icon.
Once the UART terminal is opened, the window takes on a new form. At the top of the tab are two buttons, one for adjusting the parameters of the UART terminal and the other for connecting the UART terminal. The tab's lower part is reserved for displaying the achieved results. Before connecting, the terminal has a Disconnected status, indicating that the terminal is not yet active. Before connecting, it is necessary to check the set parameters of the UART terminal. Click on the "OPTIONS" button.
In the newly opened UART Terminal Options field, we check if the terminal settings are correct, such as the set port and the Baud rate of UART communication. If the data is not displayed properly, it is possible that the Baud rate value is not set correctly and needs to be adjusted to 115200. If all the parameters are set correctly, click on "CONFIGURE".
The next step is to click on the "CONNECT" button, after which the terminal status changes from Disconnected to Connected in green, and the data is displayed in the Received data field.
Software Support
Library Description
This library contains API for LLC-SPI Click driver.
Key functions:
llcspi_generic_write- LLC SPI writellcspi_generic_read- LLC SPI readllcspi_generic_transfer- LLC SPI transfer
Open Source
Code example
This example can be found in NECTO Studio. Feel free to download the code, or you can copy the code below.
/*!
* \file
* \brief llcspi Click example
*
* # Description
* This application is converter for logic signals.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initialization device init
*
* ## Application Task
* Counter passes through the loop and logs the value of the counter on the bargraph display
*
* *note:*
* Connection between BarGraph and LLC-SPI is made through SPI interface.
* You can connect a BarGraph click to LLC-SPI click with the wires to make connection between click boards.
* We use the BarGraph click to demonstrate the functions of the LLC-SPI click.
*
* \author MikroE Team
*
*/
// ------------------------------------------------------------------- INCLUDES
#include "board.h"
#include "log.h"
#include "llcspi.h"
// ------------------------------------------------------------------ VARIABLES
static llcspi_t llcspi;
static log_t logger;
// ------------------------------------------------------ APPLICATION FUNCTIONS
void application_init ( void )
{
log_cfg_t log_cfg;
llcspi_cfg_t cfg;
/**
* Logger initialization.
* Default baud rate: 115200
* Default log level: LOG_LEVEL_DEBUG
* @note If USB_UART_RX and USB_UART_TX
* are defined as HAL_PIN_NC, you will
* need to define them manually for log to work.
* See @b LOG_MAP_USB_UART macro definition for detailed explanation.
*/
LOG_MAP_USB_UART( log_cfg );
log_init( &logger, &log_cfg );
log_info( &logger, "---- Application Init ----" );
// Click initialization.
llcspi_cfg_setup( &cfg );
LLCSPI_MAP_MIKROBUS( cfg, MIKROBUS_1 );
llcspi_init( &llcspi, &cfg );
}
void application_task ( void )
{
uint16_t convert;
uint8_t tmp[ 2 ];
uint8_t cnt;
// BarGraph display
for ( cnt = 0; cnt <= 10; cnt++ )
{
convert = ( uint16_t ) ( ( 1 << cnt ) - 1 );
tmp[ 1 ] = ( convert & 0x00FF );
tmp[ 0 ] = ( convert & 0xFF00 ) >> 8;
llcspi_generic_write( &llcspi, tmp, 2 );
Delay_ms( 1000 );
}
}
void main ( void )
{
application_init( );
for ( ; ; )
{
application_task( );
}
}
// ------------------------------------------------------------------------ END
