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➜ Electronics
➜ G-Pascal
➜ SPI support added to the G-Pascal EEPROM
SPI support added to the G-Pascal EEPROM
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Posted by
| Nick Gammon
Australia (23,122 posts) Bio
Forum Administrator |
Date
| Tue 08 Mar 2022 12:24 AM (UTC) Amended on Tue 08 Mar 2022 12:25 AM (UTC) by Nick Gammon
|
Message
| Support for SPI devices has been added to version 4.02 of the G-Pascal system. The video below shows a MCP23017 port-expander controlling 16 LEDs under instruction from some simple code written in Assembler.
- An I2C real-time clock (DS1307) which is being polled for the current time of day
- An I2C 16-port expander chip (MCP23017) which is being used to show a rotating display of LEDs
- An SPI 7-segment display board using the MAX7219 chip which is showing the current time (2:59 pm).
Code used in the above demo:
jmp begin
;---------------------------------------------
; MAX7219 registers
;---------------------------------------------
MAX7219_REG_NOOP = $00 ; No operation - used for cascading multiple chips
MAX7219_REG_DIGIT0 = $01 ; Write to digit 1
MAX7219_REG_DIGIT1 = $02 ; Write to digit 2
MAX7219_REG_DIGIT2 = $03 ; Write to digit 3
MAX7219_REG_DIGIT3 = $04 ; Write to digit 4
MAX7219_REG_DIGIT4 = $05 ; Write to digit 5
MAX7219_REG_DIGIT5 = $06 ; Write to digit 6
MAX7219_REG_DIGIT6 = $07 ; Write to digit 7
MAX7219_REG_DIGIT7 = $08 ; Write to digit 8
MAX7219_REG_DECODEMODE = $09 ; Decode mode for each digit: 1 = decode, 0 = no decode (one bit per digit)
MAX7219_REG_INTENSITY = $0A ; Intensity: 0x00 to 0x0F
MAX7219_REG_SCANLIMIT = $0B ; Scan limit: 0x00 to 0x07 - how many digits to display (ie. 1 to 8)
MAX7219_REG_SHUTDOWN = $0C ; Shutdown: 0x00 = do not display, 0x01 = display
MAX7219_REG_DISPLAYTEST = $0F ; Display test: 0x00 = normal, 0x01 = display all segments
; our variables
counter dfw 0
display_work dfb 0
;---------------------------------------------
; begin test code
;---------------------------------------------
begin:
lda #0 ; mode 0 SPI
jsr spi_init
lda #MAX7219_REG_SCANLIMIT ; show 8 digits
ldx #7
jsr spi_send_two_bytes
lda #MAX7219_REG_DECODEMODE ; use digits (not bit patterns)
ldx #$FF
jsr spi_send_two_bytes
lda #MAX7219_REG_DISPLAYTEST ; no display test
ldx #0
jsr spi_send_two_bytes
lda #MAX7219_REG_INTENSITY ; character intensity: range: 0 to 15
ldx #7
jsr spi_send_two_bytes
lda #MAX7219_REG_SHUTDOWN ; not in shutdown mode (ie. start it up)
ldx #1
jsr spi_send_two_bytes
display_loop:
jsr serial_available
cmp #'C'-$40 ; ctrl+C?
bne loop_no_abort
rts ; we are done!
loop_no_abort:
;
; we will display an incrementing number
;
inc counter
bne display_loop1
inc counter+1
;
; turn the number into decimal digits
;
display_loop1:
lda counter
sta VALUE
lda counter+1
sta VALUE+1
stz VALUE+2
jsr binary_to_decimal
;
; the number is in bcd_result, take each byte, remove the high-order bits
; and send to the display
;
ldy #0 ; start with the high-order digit
lda #8
sta display_work
display_loop2:
lda bcd_result,y
and #$0f
tax
phy
lda display_work ; will be sending to 7,6,5,4,3,2,1,0 in that order
dec display_work
jsr spi_send_two_bytes
ply
iny
cpy #8 ; stop after 8 digits
bne display_loop2
;
; wait briefly
;
loop_delay:
ldx #<400
ldy #>400
jsr delay
bra display_loop
This video shows it controlling a bank of 8 64-pixel LEDs:
Documentation about it at http://www.gammon.com.au/G-Pascal/spi.htm |
- Nick Gammon
www.gammon.com.au, www.mushclient.com | Top |
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