RaspiElfDisplay < Cosmac

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Long time ago I built a LED display and a hex keypad for my [[Cosmicos][COSMICOS]]. I lend the COSMICOS and the extensions to a friend's brother and I saw the parts never again. Thanks to Lee Hart's [[http://www.sunrise-ev.com/membershipcard.htm][1802 Membership Card]] I own a 1802 SBC again. Now I need a display and a [[RaspiElfKeypad][keypad]] for this gem.
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---+ Hardware
TIL311 hexadecimal displays were to expensive for me 35 years ago and now they are not easy to get (and still expensive). The 4×7 rounded font looks far better than the seven-segment display especially the lower case hex display letters. But there is an alternative: [[http://optoelectronics.liteon.com/upload/download/ds-30-97-087/ltp-305hr.pdf][LTP-305]] from LITEON. They have no integrated driver, but the matrix LED driver IC [[http://www.issi.com/WW/pdf/IS31FL3730.pdf][IS31FL3730]] can drive two of them. And better there is a [[https://shop.pimoroni.com/products/microdot-phat][PCB HAT]] with 6 LTP-305 and 3 !IS31FL3730 on it from Pimoroni ready for the Raspberry Pi. Four digits for the address and two digits for data! 

| %IMAGE{"%PUBURLPATH%/Cosmac/RaspiElfDisplay/til311.jpg" type="thumb" caption="TIL311 Hexadecimal Display"}% \
| %IMAGE{"%PUBURLPATH%/Cosmac/RaspiElfDisplay/LED_module.jpg" type="thumb" caption="LTP-305 Dot Matrix Display"}% \
| %IMAGE{"%PUBURLPATH%/Cosmac/RaspiElfDisplay/Microdot_pHAT.jpg" type="thumb" caption="Microdot_pHAT on Raspberry Pi Zero"}% |
| %IMAGE{"%PUBURLPATH%/Cosmac/RaspiElfDisplay/keypad-display.jpg" type="thumb" caption="Keypad and display"}% |

   * https://shop.pimoroni.com/products/microdot-phat
   * Pinout https://pinout.xyz/pinout/micro_dot_phat#

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---+ Software for the Raspberry Pi
The Raspi controls the display through its I2C interface.

I still want to use the [[http://www.sunrise-ev.com/membershipcard.htm][1802 Membership Card's]] Front Panel Card. That means I have to use the D-SUB connector. But there is no address bus on this connector, therefore the address is only known as long as the DMA (load mode, counting the DMA cycles) is used. The data bus is neither available, you will see the data in the load mode (DMA) and the output port (LEDs) during the run mode.   

There is Python Library and Examples for Micro Dot pHAT on [[https://github.com/pimoroni/microdot-phat][GitHub]] from Pimorini itself. But I prefer plain C and wrote my own hex display driver [[https://github.com/spyren/RaspiElf/blob/master/tools/microdot_phat_hex.c][microdot_phat_hex.c]]

Check for the I2C device:
<pre>
pi@cosmac:~/elf $ <b>ls /dev/*i2c*</b>
/dev/i2c-1
</pre>

Detect the I2C chips:
<pre>
pi@cosmac:~/elf $ <b>i2cdetect -y 1</b>
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- 61 62 63 -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --
</pre>
61, 62, and 63 are the I2C addresses of the !IS31FL3730 chips.

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---+ How to get and build the RaspiElf Display Software

The =elfdisplay= is part of the RaspiElf tools package. See RaspiElf#How_to_get_and_build_the_RaspiEl
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---+ Operating Modes (shown by decimal points) 
---++ Load
<pre>
            #        #####        ###        #####       #####      ######  
           ##       #     #      #   #      #     #     #     #     #     # 
          # #       #     #     #     #           #     #           #     # 
            #        #####      #     #      #####      #           #     # 
            #       #     #     #     #     #           #           #     # 
            #       #     #      #   #      #           #     #     #     # 
      <b>OOO</b> #####      #####        ###       ####### ###  #####      ######
</pre>
  
---++ Run
<pre>
            #        #####        ###        #####       #####      ######  
           ##       #     #      #   #      #     #     #     #     #     # 
          # #       #     #     #     #           #     #           #     # 
            #        #####      #     #      #####      #           #     # 
            #       #     #     #     #     #           #           #     # 
            #       #     #      #   #      #           #     #     #     # 
          ##### <b>OOO</b>  #####        ###       ####### ###  #####      ######
</pre>
  
---++ Wait
<pre>
            #        #####        ###        #####       #####      ######  
           ##       #     #      #   #      #     #     #     #     #     # 
          # #       #     #     #     #           #     #           #     # 
            #        #####      #     #      #####      #           #     # 
            #       #     #     #     #     #           #           #     # 
            #       #     #      #   #      #           #     #     #     # 
          #####      #####  <b>OOO</b>   ###       ####### ###  #####      ######
</pre>
  
---++ Address
<pre>
            #        #####        ###        #####       #####      ######  
           ##       #     #      #   #      #     #     #     #     #     # 
          # #       #     #     #     #           #     #           #     # 
            #        #####      #     #      #####      #           #     # 
            #       #     #     #     #     #           #           #     # 
            #       #     #      #   #      #           #     #     #     # 
      ### #####      #####        ###  <b>OOO</b>  ####### ###  #####      ######
</pre>
  
---++ Memory Protect
<pre>
            #        #####        ###        #####       #####      ######  
           ##       #     #      #   #      #     #     #     #     #     # 
          # #       #     #     #     #           #     #           #     # 
            #        #####      #     #      #####      #           #     # 
            #       #     #     #     #     #           #           #     # 
            #       #     #      #   #      #           #     #     #     # 
      ### #####      #####        ###       ####### ###  #####  <b>OOO</b> ######
</pre>


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---+ TIL311 Emulator
The TIL311 has following inputs:
   * Data Inputs A, B, C, D
   * Latch Input
   * Blanking Input
   * (Right and Left Decimal)

For 6 digits we need 36 GPIOs. Without blanking 32 GPIOs, and shared latch input 25 GPIOs. The Raspberry Pi has 26 GPIOs, the spare GPIO ca be used for an additional latch input, then we have a latch for the data and a latch for the address. 

Usually the CDP1802 computers use a multiplexed address bus e.g. the [[http://www.sparetimegizmos.com/Hardware/Elf2K.htm][Spare Time Gizmo's Elf 2000]] display:
   * Databus
      * 8 Data Inputs
      * no strobe
   * Adressbus
      * 8 Data Inputs
      * 2 Latch Inputs
This is a total of 18 GPIOs. Do not forget: the Raspberry Pi GPIOs are not 5 V compatible!

Is anybody interested in a TIL311 emulator? The only problem to write a program for the Raspi is to be fast enough for the strobe signal. Linux is not a Real Time Operating System (RTOS), and it is easy to miss a strobe signal, even if we use interrupts.
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-- %USERSIG{PeterSchmid - 2017-11-26}%

---++!! Comments
Attachments
Topic attachments
I	Attachment	History	Action	Size	Date	Who
jpg	LED_module.jpg	r1	manage	79.2 K	2018-05-03 - 20:14	PeterSchmid
jpg	Microdot_pHAT.jpg	r1	manage	164.3 K	2018-05-03 - 20:17	PeterSchmid
jpg	keypad-display-s.jpg	r1	manage	56.2 K	2018-05-20 - 18:46	PeterSchmid
jpg	keypad-display.jpg	r1	manage	718.0 K	2018-05-20 - 16:12	PeterSchmid
pdf	til311-e4-519224.pdf	r1	manage	90.5 K	2018-05-04 - 19:27	PeterSchmid
jpg	til311.jpg	r1	manage	96.4 K	2018-05-03 - 20:14	PeterSchmid
Topic revision: r13 - 2018-09-28 - PeterSchmid