Demo board clock output

Hasin · 2009-11-27 11:03

Hi all,
I'm new to propeller thing and I need your help, please. I have propeller demo board, ay0438 circuit and LCD 7-segment display. I need to connect the demo board with ay0438. I need one port to DATA, one port for LOAD and one for CLOCK. I managed first two ports but I don't know how create a code for clock port.

Don't know if I explained it enough, but If anyone could help me I will be very happy.

Thanks for all replies

PS: Sorry for my English

MagIO2 · 2009-11-27 12:10

With that little information you gave, there are lots of possibilities.

1. Do you code in SPIN or in PASM?
2. Do you have some timing requirements/restrictions?
3. Do you want to code it by yourself, or would you be fine with a driver that already works?
4. Why didn't you provide the code you already have?

On a quick glance it should be possible to use an SPI driver for that ... maybe you have to tweak it a bit - for example to limit it to 1,5MHz clock frequency.

In general:
I suppose you already have the datasheet for the AY0438. There you find a timing diagram which shows you when you have to set and when you have to clear the clock-pin. So, whatever your code looks like currently, find the places where you have to clear the pin and where you have to set the pin and put the right instructions there.

In SPIN you'd do for setting or clearing that one bit:
outa[noparse][[/noparse] CLK_PIN ]~
outa[noparse][[/noparse] CLK_PIN ]~~

For a general purpose PASM solution you need a mask where only the pin is set:
dat clk_mask long 1<|CLK_PIN

... and then you do for setting or clearing that one bit:
or outa, clk_mask
andn outa, clk_mask

This is only the easiest solution ... maybe it makes sense to use a counter to do that, maybe not ... that depends on the missing information ;o)

StefanL38 · 2009-11-27 19:42

Hello Hasin,

nice find this chip.
a shiftregister with latch and 32 outputs in one DIP-package.
replaces four 74HC595'ers and suits perfect to the 32bits of a long.

Stefan

Sapieha · 2009-11-28 00:38

Hi StefanL38

I use that one to Drive leds
MAX6954

Regards

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Nothing is impossible, there are only different degrees of difficulty.
For every stupid question there is at least one intelligent answer.
Don't guess - ask instead.
If you don't ask you won't know.
If your gonna construct something, make it·as simple as·possible yet as versatile as posible.

Sapieha

StefanL38 · 2009-11-28 08:28

Hello Hasin,

the AY0438-chip has a serial interface this means

repeat
set the data-pin to the wished value
and then you switch the clock pin low-high-low (or maybe (high-low-high) depending on what the datasheet says

The data-signal and clock-signal have to be switched after each other but the clocksignal-pulse must be done before
setting the data-pin to the value of the next bit.

Through the clock-pulse the databit is shifted in into the shiftregister

After you finished shifting in all 32 databits
you give one pulse on the load-pin. This signal transfers the bitvalues to the latch and the voltages on the output-pins change
to the bitstates stored in the latch

Come on ! Play around with the data-pin, clock-pin and the load-pin.

I mean to learn how it works program some hardcodes pulse-sequences
test which element of your display show up if you give a signal on the output-pin no Seg1, Seg2, Seg3 of the AY0438
draw a little picture of these segments
connect your display to the outputs of the AY0438

connect the AY0438 to the prop-pins 16-18 and run the program below
look what result you get on the AY0438-SEG-pins
If you do the low-high-switching right you get the same bitpattern on the SEG-pins like you have coded them in the spin-code

CON
  _clkmode      = xtal1 + pll16x                        ' use crystal x 16
  _xinfreq      = 5_000_000


  DataPin   = 16
  Clock_Pin = 17
  Load_Pin  = 18

  OutPut = 1
  Input  = 0

  Low    = 0
  High   = 1


Pub Test_AY0438

  DirA[noparse][[/noparse] DataPin ]   := OutPut 'configure IO-pins as output-pins
  DirA[noparse][[/noparse] Clock_Pin ] := OutPut
  DirA[noparse][[/noparse] Load_Pin ]  := OutPut


  OutA[noparse][[/noparse] DataPin ]   := High   'set databit high = 1

  'create a Clock-pulse
  OutA[noparse][[/noparse] Clock_Pin ] := High
  OutA[noparse][[/noparse] Clock_Pin ] := Low
  OutA[noparse][[/noparse] Clock_Pin ] := High
  

  OutA[noparse][[/noparse] DataPin ]   := Low
  
  'create a Clock-pulse
  OutA[noparse][[/noparse] Clock_Pin ] := High
  OutA[noparse][[/noparse] Clock_Pin ] := Low
  OutA[noparse][[/noparse] Clock_Pin ] := High


  OutA[noparse][[/noparse] DataPin ]   := High
  
  'create a Clock-pulse
  OutA[noparse][[/noparse] Clock_Pin ] := High
  OutA[noparse][[/noparse] Clock_Pin ] := Low
  OutA[noparse][[/noparse] Clock_Pin ] := High


  'create a load-pulse
  OutA[noparse][[/noparse] Load_Pin ]   := Low
  OutA[noparse][[/noparse] Load_Pin ]   := High
  OutA[noparse][[/noparse] Load_Pin ]   := Low

if this code switches right then the bitpattern should be
seg1 = high
seg2 = low
seg3 = high

Maybe you are thinking "ey that's far OFF of what I want to to in the end !

SURE that's far off ! But you will reach the point that everything works MUCH faster if you understand from scratch how the chip works

If you start at the level: "let's shift in the 32bits from a separate cog by using a downloaded object"
you maybe stumble around for days or even weeks until everything works properly
with a lot of help of experienced propeller-users and if another bug occures you still DON'T know where to search.

If you understand it from scratch you will be the expert in 1 week yourself about bitshifting and bitbanging towards the AY0438-chip

A variant to play around is to write a program that waits for a (debounced) button to be pressed before each step to create one pulse
and have LEDs connected parallel to the AY0438-chip-data, clock and load-pins.
Then you have a visual feedback about the logical state of the IO-pins
and by pressing the button you can single-step through the process of how data, clock and load-signal change
By varying the pulse-sequences of the clock from low-high-low to high-low-high and load-pulse low-high-low, high-low-high
you will find out how it has to be done to shift in the bits the right way

another way could be to replace the button through a serial connection that waits to receive a certain byte before
executing the next step

best regards

Stefan

Demo board clock output

Comments