Upgrading real world legacy systems

Transcription

1 Julie Porter, Delectra

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9 Look for places to add interfaces. In our example there were switches. By mapping these to a strap header we can expose some GPIO Pins. We now have a debug pod which is effectively the same as an Arduino.

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11 Distill the schematic into modules Can memory mapped devices be replaced by SPI or I2C This example shows GPIO,MIDI and a bridge to RS485 SPI and I2C can be seen as potential expansion points.

12 Arduino shield from schematic.

13 Abstracting from 8051 to AVR Make a copy of the 8051 ASM source. Comment all the lines. Register Naming. AVR R20,R21 are good choices to name ACC and BCC. Mapping the DPTR is more complex. These are best mapped to the lower 16 of the AVR and moved into X,Y and Z through convenience macros. These macros will make translating to C/C++ as used by the IDE more apparent. Add the code back in using the new syntax, retain function calls.

14 What A PLC needs to do Read switches, close relays, measure time. A pipe organ relay is a PLC. The structure of the switch stack may be where ladder logic gets it s name. The physical layer can be represented by RS485. In more complex systems CAT 5 can be used through UDP/IP Most legacy systems will have a serial or parallel port for diagnostics/upgrading this is a good place to start the conversion Next we look at the LEDs, Switches and Segment Panels

15 mapping these to a strap header we can expose some GPIO Pins. In this case there was enough GPIO to connect an LCD. We now have extended our debug pod with 4 LEDs A display and I2C. This Pod can also sequence MIDI.

16 Arduino is good at reading LEDS and Switches. This can be abstracted via a state machine inside a master loop. It is good practice to set up the watchdog system and exception vectors. Use a token ack/nac inside the main state loop to reset the dog and prevent watchdog lockouts. (If you must hang light or blink a led in the crash loop.) In most cases that log data a File System is used. File systems are just blocks of memory connected to SPI or I2C. This is where the convenience macro come in to play.

17 Does the filing system require an RTOS? (Probably not) Use counting semaphores. Most modern architectures provide user flags/exceptions. The main heartbeat can be shown on a LED. The legacy UI is a good place to start the state machine re-design this can be built from scratch using the users manual. In our example we have the simple IDLE/Play/Record states on the front panel. The PC link handles the setup. Having the state in both places makes it easier to debug and use the system. Many rom and flash memory can be handled by an SD card on the SPI or I2C bus.

18 Real world example Adding play record to a stand alone relay Record was constructed first as a data logger capturing the network frames. Next the playback was written to sequence the data into the same waveform as the recorder. External to the hardware, scripts were written to convert the recorded data to MIDI. The recorded music can then be played on a hardware or software synth such as Hauptwerk or Fluidsynth.

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20 The lash up. Provides a test bed for expansion interfaces In this example we will connect to a rank of virtual pipes through MIDI using the jorgan synth.

21 We can now control the system from a simple app. Jorgan is a java app that can run on desktop, laptop or even a raspberry pi.

22 Extending into the world of IoT we can add a blue tooth module that talks to the SPI bus. As our system is modular, we can use the serial backchannel to receive the command strings instead of the button presses and LCD screen. Many of these modules have a built in interface to the phone OS. The example shown is from Singapore called an Anniken Andee. It has a setup app which allows for quick simulation of the button/lcd screen. By separating out our state machine we can enter it into the IDE and have a User Interface running in a short time.

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24 Speaker/Author Details Youtube: spiralsheepdoll

25 Thank You!