POD Tutorial

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In this first tutorial, we will learn how to use POD with a simple example project for an APF27 board. The project is described in figure 1. It is composed of 3 virtual components:

  • blink : blink is the instance name of a led (virtual component) that can «blink» by simply writing a value in a register.
  • push : push is the instance name of a button (virtual component) that can generate an interrupt when pushed/released. The state of the button can be read in a register.
  • i2c : i2c is the instance name of the i2cocore virtual component (from OpenCores.org). This component is an i2c bus controller.
figure 1 - Project example for tutorial


See POD installation guide to learn how to install it.

Note Note: This tutorial is written for apf27_dev a LED is already soldered on fpga. The fpga bank1 must be powered with 3.3V (connect pin 39 and pin 1 on J20 header)


If POD is correctly installed, simply type :

$ pod 

Playing with POD

POD is a console program composed of several environments described in figure 2.

figure 2 - POD console architecture

To enter in an environment, simply write its name from the parent environment.

POD> synthesis 

For a complete list of the available commands type help

POD> help

Documented commands (type help <topic>):
EOF               create            history          ls              shell     
addbusclock       delbusconnection  info             printxml        simulation
addinstance       delinstance       generateintercon quit            source    
autoconnectbus    delpinconnection  listcomponents   report          synthesis 
check             description       listforce        savehistory     generatetop       
closeproject      driver            listinstances    saveproject     version   
connectbus        eof               listinterfaces   selectplatform
connectinterface  exit              listmasters      setaddr       
connectpin        getmapping        listplatforms    setforce      
connectport       help              load             setgeneric    

A short help description is although available for each command.

POD> help listcomponents
 listcomponents [componenttype]
        List components available in the library

Command completion and argument completion can be done by using the <TAB> key :

POD> help list<TAB>
listcomponents  listinterfaces  listplatforms   
listinstances   listmasters  
POD> help list

System commands can be used with «!» before:

POD> !echo "POD is really useful"
POD is really useful

Project creation

figure 3 - Empty i2cledbutton project

To create a project, enter the create command in the project environment:

POD> create i2cledbutton
Project i2cledbutton created

The i2cledbutton project is now created and saved.

The target platform has to be selected by means of the selectplatform command :

project:i2cledbutton> selectplatform standard.apf27
[INFO]   : No platform in project
Component platform added as apf27
Component imx27_wb16_wrapper added as imx27_wb16_wrapper00
Component rstgen_syscon added as rstgen_syscon00
Component irq_mngr added as irq_mngr00


By selecting this platform, several components will be automaticaly added by POD:

  • imx27_wb16_wrapper: this component is used to convert the i.MX27 processor bus to the wishbone (16bits data) bus.
  • rstgen_syscon : this component manages the clock and the reset for the design.
  • irq_mngr : this is a wishbone16 slave which manages the interrupts generated by the other components and which propagates them to the processor.
figure 4 - Platform loaded with their default components

Adding components

Components are organized by category in the library, to list the categories, use listcomponents:

project:i2cledbutton> listcomponents 
components  logics   syscons     test   wrappers

And to list the components under a category use listcomponents again with the category name in parameter:

project:i2cledbutton> listcomponents components
sp_vision_configure      bram              uart16750   spartan_selectmap
industrial_output        anybus_interface  simplegpio  button           
industrial_serial_input  led               uart16550   sja1000          
i2cocore                 pod_gpio          irq_mngr  

The components will be loaded with the command addinstances:

POD:i2cledbutton> help addinstance
 addinstance <componenttype>.<componentname>.[componentversion] [newinstancename]
        Add component in project

The second parameter is used to give the instance name of the component in the project.

POD:i2cledbutton> addinstance components.button push
Component button added as push

POD:i2cledbutton> addinstance components.led.wb16 blink
Component led added as blink

POD:i2cledbutton> addinstance components.i2cocore.wb16 i2c
Component i2cocore added as i2c

Note: some components like the led may have several versions depending on the Wishbone bus size for example.

figure 4 - Components loaded

Internal pin connections

push and i2c components have output pins to generate interrupts. These pins have to be connected to the interrupt manager "irq_mngr00".

figure 5 - Internal interrupts connections

A complete description of an instance in the project can be displayed with the info command:

project:i2cledbutton> info i2c
Instance name :i2c
Component  name :i2cocore
description : A simple button ip
             id : 1
        wb_size : 16
irq             :
     inta_o          s1
i2c             :
     scl             s1
     sda             s1
swb16            Base address:0x0
     rst_i           s1
     clk_i           s1
     adr_i           s4
     dat_i           s16
     dat_o           s16
     we_i            s1
     stb_i           s1
     ack_o           s1
     cyc_i           s1

This command gives the interfaces, the ports and the size of the ports (s1, s16, ...). We want to connect the interrupt port pin number 0, named inta_o and part of the irq interface, to the irq_mngr00.

POD:i2cledbutton> info irq_mngr00
Component name :irq_mngr00
Instance  name :irq_mngr
description : Manage interruptions.
             id : 1
      irq_level : '1'
      irq_count : 1
candr           :
     gls_clk         s1
     gls_reset       s1
swb16            Base address:0x0
     wbs_s1_address  s2
     wbs_s1_readdata s16
     wbs_s1_writedata s16
     wbs_s1_ack      s1
     wbs_s1_strobe   s1
     wbs_s1_cycle    s1
     wbs_s1_write    s1
irq             :
     irqport         s16
ext_irq         :
     gls_irq         s1
        pin 0: -> apf27.fpga.TIM1.0

The targeted port in the irq_mngr is irqport part of the irq interface. To establish the connection, the connectpin command will be used:

POD:i2cledbutton> connectpin irq_mngr00.irq.irqport.0 i2c.irq.inta_o.0

Same thing for the push button :

POD:i2cledbutton> connectpin irq_mngr00.irq.irqport.1 push.int_button.irq.0
pin connected

The info command can be used to verify that the connection is correctly performed:

POD:i2cledbutton> info irq_mngr00
Component name :irq_mngr00
Instance  name :irq_mngr
description : Manage interruptions.
             id : 1
      irq_level : '1'
      irq_count : 2
candr           :
     gls_clk         s1
     gls_reset       s1
swb16            Base address:0x0
     wbs_s1_address  s2
     wbs_s1_readdata s16
     wbs_s1_writedata s16
     wbs_s1_ack      s1
     wbs_s1_strobe   s1
     wbs_s1_cycle    s1
     wbs_s1_write    s1
irq             :
     irqport         s16
        pin 0: -> i2c.irq.inta_o.0
        pin 1: -> push.int_button.irq.0
ext_irq         :
     gls_irq         s1
        pin 0: -> apf27.fpga.TIM1.0

External pin connections

Connecting an external pin is done the same way as for an internal pin by giving the name of the platform in place of the instance name. In the apf27 platform, the pin name can be found in FPGA schematic [1]. The name of the interface is fpga for the apf27. In this example we will connect the button, the led and the i2c to the apf27DevFull connector X7 (figure 6).

figure 5 - FPGA led connection on apf27Devfull

We just have to connect the pins as following :

POD:i2cledbutton> connectpin blink.int_led.led.0 apf27.fpga.IO_L24P_1
POD:i2cledbutton> connectpin push.int_button.button.0 apf27.fpga.IO_L24N_1 
POD:i2cledbutton> connectpin i2c.i2c.sda apf27.fpga.IO_L20N_1
POD:i2cledbutton> connectpin i2c.i2c.scl apf27.fpga.IO_L20P_1
figure 6 - external connections

Bus and clock connections

  • Bus
figure 7 - Wishbone bus connections

To connect a bus, the master bus interface is used as first argument of the connectbus command, the second argument being the slave bus interface:

POD:i2cledbutton> connectbus imx27_wb16_wrapper00.mwb16 blink.swb16
setting base address 0x0 for  blink.swb16

POD:i2cledbutton> connectbus imx27_wb16_wrapper00.mwb16 push.swb16
setting base address 0x4 for  push.swb16

POD:i2cledbutton> connectbus imx27_wb16_wrapper00.mwb16 i2c.swb16
setting base address 0x20 for  i2c.swb16

POD:i2cledbutton> connectbus imx27_wb16_wrapper00.mwb16 irq_mngr00.swb16
setting base address 0x40 for  irq_mngr00.swb16
  • clock & reset
figure 8 - Syscon connection

Clock and reset are seen like a standard bus, to connect it, simply use connectbus:

project:i2cledbutton> connectbus rstgen_syscon00.candroutput imx27_wb16_wrapper00.candrinput
No addressing value in this type of bus
  • autoconnect

Bus and clock connections can be automatically performed with the autoconnect command. This command works only for "classical" architectures and with recognized busses.

POD:i2cledbutton> autoconnectbus

Intercon generation

Once the connections done, the Intercons components has to be generated. Intercons are components responsible for decoding the addresses and for routing bus signals. Intercons must be generated for each master bus.

  • for wrapper master wishbone bus
POD> generateintercon imx27_wb16_wrapper00.mwb16
Intercon with name : imx27_wb16_wrapper00_mwb16_intercon Done
Component imx27_wb16_wrapper00_mwb16 added as imx27_wb16_wrapper00_mwb16_intercon
  • for syscon master candr bus
POD> generateintercon rstgen_syscon00.candroutput
Intercon with name : rstgen_syscon00_candroutput_intercon Done
Component rstgen_syscon00_candroutput added as rstgen_syscon00_candroutput_intercon
figure 8 - Intercon

Top generation

figure 9 - Top

The Top component is the component responsible for connecting all instances in the FPGA. The Top can be generated with the generatetop command

POD:i2cledbutton> generatetop

Mapping for interface mwb16:
Address  | instance.interface             | size
0x0 |                    blink.swb16 |          4
0x4 |                     push.swb16 |          4
0x08 |                       --void-- |         24
0x20 |                      i2c.swb16 |         32
0x40 |               irq_mngr00.swb16 |          8

Top generated with name : top_i2cledbutton.vhd


In the apf27 platform, the FPGA is a Spartan3A from Xilinx. This means that the synthesis of the project can only be done with ISE. Fortunately, Xilinx provides the ISE Webpack freely on its website [2].

POD has to generate a project that ISE can understand. This can be accomplished from the synthesis environment :

POD:i2cledbutton-tutorial> synthesis

Then the tool used for the synthesis has to be specified with the selecttoolchain command:

POD.synthesis> selecttoolchain ise

After that we can generate an ISE project with the generateproject command.

POD> synthesis
POD.synthesis> selecttoolchain ise
POD.synthesis> generateproject
Make directory for imx27_wb16_wrapper
Make directory for rstgen_syscon
Make directory for irq_mngr
Make directory for button
Make directory for led
Make directory for i2cocore
Make directory for rstgen_syscon00_candroutput
Make directory for imx27_wb16_wrapper00_mwb16

Constraint file generated with name : /home/fabien/tmp/i2cledbutton/synthesis/i2cledbutton.ucf

TCL script generated with name : i2cledbutton.tcl

As you can see, POD generates although a TCL script that can be executed by ISE. This script eases the synthesis process.

figure 10 - Bitstream generation with ISE Webpack

In the Tcl tab (1), change the default directory to the synthesis directory (2), find the tcl script you want to execute (3, under Windows type dir instead of ls) and start it with the source command (4).

Note Note: To use this tutorial with APF51, generate binary file .bin instead of bitstream .bit file.

The resulting bitstream (binary FPGA synthetized code) top_i2cledbutton.bit can be found in the i2cledbutton_tutorial/objs directory.

Warning Warning: There is a bug with ISE-13.x and upper, when tcl script is launched, the constraints file (ucf) is not read and ISE choose FPGA pinout randomly. To avoid this problem, once the script is sourced, re-launch the entire process by clicking right on «Generate Programming File» en selecting «re-run all»


If a simulation is required, POD can generate a template for the whole project. To do this, enter in the simulation environment :

POD.project:i2cledbutton_tutorial> simulation

First select your toolchain (here it's ghdl):

POD.project:i2cledbutton_tutorial.simulation> selecttoolchain ghdl

To generate the testbench and the makefile use the command:

POD.project:i2cledbutton_tutorial.simulation> generateproject

Testbench with name : /home/fabien/projectpod/software/pod/tests/i2cledbutton_tutorial/simulation/top_i2cledbutton_tutorial_tb.vhd Done

Makefile generated with name : /home/fabien/projectpod/software/pod/tests/i2cledbutton_tutorial/simulation/Makefile Done

Now, you just have to modify the top_i2cledbutton_tutorial_tb.vhd file to add your own tests under the stimulis process.

stimulis : process
-- write stimulis here
wait for 10 us;
assert false report "End of test" severity error;
end process stimulis;

You can then start the simulation with make ghdl-simu and launch make ghdl-view to view the generated chronograms with gtkwave.


Numbers of components have a driver template for different operating systems. POD can fill these templates with the informations contained in the project.

From the driver environment,

POD:i2cledbutton_tutorial> driver

choose the targeted platform:

POD:i2cledbutton_tutorial.driver> selecttoolchain armadeus

And generate the driver project :

POD:i2cledbutton_tutorial.driver> generateproject
No driver for imx9328_wb16_wrapper
No driver for rstgen_syscon
Create directory for irq_mngr driver
Create directory for button driver
Create directory for led driver
Create directory for i2cocore driver
No driver for imx9328_wb16_wrapper00_mwb16
Copy and fill template for irq_mngr
Copy and fill template for button
Copy and fill template for led
Copy and fill template for i2cocore

Drivers are generated and can be found in the i2cledbutton_tutorial/drivers/ directory. POD can copy this drivers to the right place in the software development tree. Select the path with selectprojecttree then copy the files with copydrivers:

POD:i2cledbutton_tutorial.driver> selectprojecttree ~/armadeus/target/linux/modules/fpga/POD

POD:i2cledbutton_tutorial.driver> copydrivers

To compile the drivers, go to your armadeus/ directory, then:

$ make linux-menuconfig
Device Drivers  --->
        [*] Support for specific Armadeus drivers --->
              *** FPGA related ***
            [*]   FPGA specific drivers and tools  --->
                [*]   Board drivers generated by POD
$ make


Once bitstream is loaded, run linux and modprobe pod linux module :

# modprobe irq_ocore
# modprobe pod_irq_mng
# modprobe led_ocore
# modprobe pod_leds
LED module BLINK inserted
# modprobe i2c-ocores-pod
# modprobe pod_board_i2c
PM: Adding info for platform:ocores-i2c-pod.0
PM: Adding info for No Bus:i2c-2
PM: Adding info for No Bus:i2c-2
# modprobe button_ocore
# modprobe pod_buttons
probing button
button button.0: PUSH: MAJOR: 248 MINOR: 0
PUSH loaded

Read A_simple_design_with_Wishbone_bus to know how to use led and button.