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Adam Taylor’s MicroZed(ish) Chronicles Part 83: Simple Communication Interfaces Part 3

Xilinx Employee
Xilinx Employee
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By Adam Taylor

 

In the last blog we had looked how we can use the SPI via both the Zynq SoC’s PS (Processor System) MIO and the PL (Programmable Logic) EMIO. To get the OLED powered up in this blog, we will use both the SPI and GPIO via the EMIO.

 

To control the OLED we need to use a number of GPIO identified in the table below and mentioned briefly in part 81:

 

 

Signal

FPGA IO

PS GPIO ID

Comment

Direction

Reset

U9

54

Active Low Reset

Output

VDD

U12

55

Active Low Digital Power Enable

Output

VBatt

U11

56

Active Low Dc/Dc Power Enable

Output

D/C

U10

57

Data / Command. Command = 0

Output

 

 

We can use these GPIO in the EMIO in exactly the same manner as we would if they were within the MIO. We need to drive these signals to meet the timings identified in the diagram below:

 

 

Image1.jpg

 

 

OLED Power Up

 

 

 

Image2.jpg 

 

OLED Power Down

 

 

We can do this using the private timer on the Zynq SoC’s CPU. Once these timings have been achieved (t1 =3us, t2 = 3 us toff = 100 ms) using the GPIO signals, we can then initialize and send commands to the OLED over the SPI bus.

 

To use the GPIO in the EMIO we have to follow the steps below:

 

  • Include the header file xgpiops.h
  • Declare the GPIO using the type XGpioPs
  • Declare a GPIO Configuration pointer using the type XGpioPs_Config
  • Look up the configuration of the GPIO using XGpioPs_LookupConfig()
  • Initialize the GPIO using XGpioPs_CfgInitialize()

 

Once we have the GPIO initialized and ready to go for each of the signals, we need to declare its direction and enable it if necessary. All of these signals are outputs so we declare them as outputs and enable the outputs before we define the initial signal states. An example of how to do this is shown below:

 

 

#define vdd 55

XGpioPs_SetDirectionPin(&Gpio, vdd, 1);

XGpioPs_SetOutputEnablePin(&Gpio, vdd, 1);

XGpioPs_WritePin(&Gpio, vdd, 1);

 

 

With the OLED powered up correctly, we can now send commands to the OLED.

 

But what commands do we send?

 

To initialize the OLED, we need to configure its built-in controller, which requires sending a 23-byte configuration string to get the OLED controller into a state where it will display information. In the next blog, we’ll then start sending information for the OLED panel to display but for now, we need to configure the controller by sending the following commands over the SPI link as provided in the OLED panel data sheet:

 

 

  1. Set the display off
  2. Set the Clock, Frequency dividers and multiplexer setting
  3. Set the display offset and start line
  4. Configure the charge pump to drive the OLED panel
  5. Configure the mapping, scan direction and pin hardware configuration
  6. Set the precharge period
  7. Set the display on

 

As I said above, these seven commands take 23 bytes. To make this process very simple, I declared a u8 array containing all of these configuration words, which can then be cycled through as we write out our commands over the SPI bus. By the end of the configuration, we can see that the OLED has come to life although nothing yet is displayed upon it. A snippet of the configuration code used can be seen below.

 

 

u8 init_vector[23] = {0xae, 0xd5, 0x80, 0xa8, 0x1f, 0xd3, 0x00, 0x40, 0x8d, 0x14, 0xa1, 0xc8, 0xda, 0x02, 0x81, 0x8f, 0xd9, 0xf1, 0xdb, 0x40, 0xa4, 0xa6, 0xaf};

for(i =0; i<23; i++){

   wr_buff[0] = (u8) init_vector[i];

   XGpioPs_WritePin(&Gpio, dc, 0); // set DC to command

   XSpiPs_SetSlaveSelect(&SpiInstance_EMIO, 0x01); //select the slave

   XSpiPs_PolledTransfer(&SpiInstance_EMIO, wr_buff, NULL, 1); //write the word

   XGpioPs_WritePin(&Gpio, dc, 1); // set DC to data

}

 

 

 

Next time, we look at how we can get the OLED to display an image

 

 

The OLED data sheet for the device in question can be found here.

 

 

 

 MicroZed Chronicles.jpg

 

 

 

 

 

 

Now, you can have convenient, low-cost Kindle access to the first year of Adam Taylor’s MicroZed Chronicles for a mere $7.50. Click here.

 

Please see the previous entries in this MicroZed Chronicles series by Adam Taylor:

 

Adam Taylor’s MicroZed(ish) Chronicles Part 82: Simple Communication Interfaces Part 2

 

Adam Taylor’s MicroZed(ish) Chronicles Part 81: Simple Communication Interfaces

 

Adam Taylor’s MicroZed Chronicles Part 80: LWIP Stack Configuration

 

Adam Taylor’s MicroZed Chronicles Chronicles Part 79: Zynq SoC Ethernet Part III

 

Adam Taylor’s MicroZed Chronicles Chronicles Part 78: Zynq SoC Ethernet Part II

 

Adam Taylor’s MicroZed Chronicles Microzed Chronicles Part 77 – Introducing the Zynq SoC’s Ethernet

 

Adam Taylor’s MicroZed Chronicles Part 76: Constraints for Relatively Placed Macros

 

Adam Taylor’s MicroZed Chronicles, Part 75: Placement Constraints – Pblocks

 

Adam Taylor’s MicroZed Chronicles, Part 73: Physical Constraints

 

Adam Taylor’s MicroZed Chronicles, Part 73: Working with other Zynq-Based Boards

 

Adam Taylor’s MicroZed Chronicles, Part 72: Multi-cycle Constraints

 

Adam Taylor’s MicroZed Chronicles, Part 70: Constraints—Clock Relationships and Avoiding Metastability

 

Adam Taylor’s MicroZed Chronicles, Part 70: Constraints—Introduction to timing and defining a clock

 

Adam Taylor’s MicroZed Chronicles Part 69: Zynq SoC Constraints Overview

 

Adam Taylor’s MicroZed Chronicles Part 68: AXI DMA Part 3, the Software

 

Adam Taylor’s MicroZed Chronicles Part 67: AXI DMA II

 

Adam Taylor’s MicroZed Chronicles Part 66: AXI DMA

 

Adam Taylor’s MicroZed Chronicles Part 65: Profiling Zynq Applications II

 

Adam Taylor’s MicroZed Chronicles Part 64: Profiling Zynq Applications

 

Adam Taylor’s MicroZed Chronicles Part 63: Debugging Zynq Applications

 

Adam Taylor’s MicroZed Chronicles Part 62: Answers to a question on the Zynq XADC

 

Adam Taylor’s MicroZed Chronicles Part 61: PicoBlaze Part Six

 

Adam Taylor’s MicroZed Chronicles Part 60: The Zynq and the PicoBlaze Part 5—controlling a CCD

 

Adam Taylor’s MicroZed Chronicles Part 59: The Zynq and the PicoBlaze Part 4

 

Adam Taylor’s MicroZed Chronicles Part 58: The Zynq and the PicoBlaze Part 3

 

Adam Taylor’s MicroZed Chronicles Part 57: The Zynq and the PicoBlaze Part Two

 

Adam Taylor’s MicroZed Chronicles Part 56: The Zynq and the PicoBlaze

 

Adam Taylor’s MicroZed Chronicles Part 55: Linux on the Zynq SoC

 

Adam Taylor’s MicroZed Chronicles Part 54: Peta Linux SDK for the Zynq SoC

 

Adam Taylor’s MicroZed Chronicles Part 53: Linux and SMP

 

Adam Taylor’s MicroZed Chronicles Part 52: One year and 151,000 views later. Big, Big Bonus PDF!

 

Adam Taylor’s MicroZed Chronicles Part 51: Interrupts and AMP

 

Adam Taylor’s MicroZed Chronicles Part 50: AMP and the Zynq SoC’s OCM (On-Chip Memory)

 

Adam Taylor’s MicroZed Chronicles Part 49: Using the Zynq SoC’s On-Chip Memory for AMP Communications

 

Adam Taylor’s MicroZed Chronicles Part 48: Bare-Metal AMP (Asymmetric Multiprocessing)

 

Adam Taylor’s MicroZed Chronicles Part 47: AMP—Asymmetric Multiprocessing on the Zynq SoC

 

Adam Taylor’s MicroZed Chronicles Part 46: Using both of the Zynq SoC’s ARM Cortex-A9 Cores

 

Adam Taylor’s MicroZed Chronicles Part 44: MicroZed Operating Systems—FreeRTOS

 

Adam Taylor’s MicroZed Chronicles Part 43: XADC Alarms and Interrupts 

 

Adam Taylor’s MicroZed Chronicles MicroZed Part 42: MicroZed Operating Systems Part 4

 

Adam Taylor’s MicroZed Chronicles MicroZed Part 41: MicroZed Operating Systems Part 3

 

Adam Taylor’s MicroZed Chronicles MicroZed Part 40: MicroZed Operating Systems Part Two

 

Adam Taylor’s MicroZed Chronicles MicroZed Part 39: MicroZed Operating Systems Part One

 

Adam Taylor’s MicroZed Chronicles MicroZed Part 38 – Answering a question on Interrupts

 

Adam Taylor’s MicroZed Chronicles Part 37: Driving Adafruit RGB NeoPixel LED arrays with MicroZed Part 8

 

Adam Taylor’s MicroZed Chronicles Part 36: Driving Adafruit RGB NeoPixel LED arrays with MicroZed Part 7

 

Adam Taylor’s MicroZed Chronicles Part 35: Driving Adafruit RGB NeoPixel LED arrays with MicroZed Part 6

 

Adam Taylor’s MicroZed Chronicles Part 34: Driving Adafruit RGB NeoPixel LED arrays with MicroZed Part 5

 

Adam Taylor’s MicroZed Chronicles Part 33: Driving Adafruit RGB NeoPixel LED arrays with the Zynq SoC

 

Adam Taylor’s MicroZed Chronicles Part 32: Driving Adafruit RGB NeoPixel LED arrays

 

Adam Taylor’s MicroZed Chronicles Part 31: Systems of Modules, Driving RGB NeoPixel LED arrays

 

 Adam Taylor’s MicroZed Chronicles Part 30: The MicroZed I/O Carrier Card

 

Zynq DMA Part Two – Adam Taylor’s MicroZed Chronicles Part 29

 

The Zynq PS/PL, Part Eight: Zynq DMA – Adam Taylor’s MicroZed Chronicles Part 28  

 

The Zynq PS/PL, Part Seven: Adam Taylor’s MicroZed Chronicles Part 27

 

The Zynq PS/PL, Part Six: Adam Taylor’s MicroZed Chronicles Part 26

 

The Zynq PS/PL, Part Five: Adam Taylor’s MicroZed Chronicles Part 25

 

The Zynq PS/PL, Part Four: Adam Taylor’s MicroZed Chronicles Part 24

 

The Zynq PS/PL, Part Three: Adam Taylor’s MicroZed Chronicles Part 23

 

The Zynq PS/PL, Part Two: Adam Taylor’s MicroZed Chronicles Part 22

 

The Zynq PS/PL, Part One: Adam Taylor’s MicroZed Chronicles Part 21

 

Introduction to the Zynq Triple Timer Counter Part Four: Adam Taylor’s MicroZed Chronicles Part 20

 

Introduction to the Zynq Triple Timer Counter Part Three: Adam Taylor’s MicroZed Chronicles Part 19

 

Introduction to the Zynq Triple Timer Counter Part Two: Adam Taylor’s MicroZed Chronicles Part 18

 

Introduction to the Zynq Triple Timer Counter Part One: Adam Taylor’s MicroZed Chronicles Part 17

 

The Zynq SoC’s Private Watchdog: Adam Taylor’s MicroZed Chronicles Part 16

 

Implementing the Zynq SoC’s Private Timer: Adam Taylor’s MicroZed Chronicles Part 15

 

MicroZed Timers, Clocks and Watchdogs: Adam Taylor’s MicroZed Chronicles Part 14

 

More About MicroZed Interrupts: Adam Taylor’s MicroZed Chronicles Part 13

 

MicroZed Interrupts: Adam Taylor’s MicroZed Chronicles Part 12

 

Using the MicroZed Button for Input: Adam Taylor’s MicroZed Chronicles Part 11

 

Driving the Zynq SoC's GPIO: Adam Taylor’s MicroZed Chronicles Part 10

 

Meet the Zynq MIO: Adam Taylor’s MicroZed Chronicles Part 9

 

MicroZed XADC Software: Adam Taylor’s MicroZed Chronicles Part 8

 

Getting the XADC Running on the MicroZed: Adam Taylor’s MicroZed Chronicles Part 7

 

A Boot Loader for MicroZed. Adam Taylor’s MicroZed Chronicles, Part 6 

 

Figuring out the MicroZed Boot Loader – Adam Taylor’s MicroZed Chronicles, Part 5

 

Running your programs on the MicroZed – Adam Taylor’s MicroZed Chronicles, Part 4

 

Zynq and MicroZed say “Hello World”-- Adam Taylor’s MicroZed Chronicles, Part 3

 

Adam Taylor’s MicroZed Chronicles: Setting the SW Scene

 

Bringing up the Avnet MicroZed with Vivado

 

 

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