From e34ee666dafc0a77f01cfac0b2c16a219ba0a368 Mon Sep 17 00:00:00 2001
From: Maddiefuzz <madeline@riseup.net>
Date: Thu, 14 May 2026 17:47:44 -0400
Subject: [PATCH] Initial commit of bme280 Z80 utility

---
 bme280_util.z80 | 155 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 155 insertions(+)
 create mode 100644 bme280_util.z80

diff --git a/bme280_util.z80 b/bme280_util.z80
new file mode 100644
index 0000000..79df48b
--- /dev/null
+++ b/bme280_util.z80
@@ -0,0 +1,155 @@
+org	100h
+
+siob_data	equ	083h
+siob_ctrl	equ	082h
+
+lcd_data	equ	0dbh
+lcd_ctrl	equ	0dah
+
+celcius_offset	equ	08ah
+pressure_offset	equ	0cah
+humid_offset	equ	09eh
+
+bdos	equ	0005h
+conout  equ	02h
+conin	equ	01h
+
+start:
+	call	init_lcd
+	call	init_siob
+	call	lcd_delay
+
+	ld	a,celcius_offset ; write celcius label
+	out	(lcd_ctrl),a
+	call	lcd_delay
+	ld	hl,clabel
+	call	print_str_to_lcd
+
+	ld	a,pressure_offset ; write pressure label
+	out	(lcd_ctrl),a
+	call	lcd_delay
+	ld	hl,plabel
+	call	print_str_to_lcd
+
+	ld	a,humid_offset ; write humidity label
+	out	(lcd_ctrl),a
+	call	lcd_delay
+	ld	hl,hlabel
+	call	print_str_to_lcd
+
+main:
+	call	read_char_b
+	call	print_char_to_lcd
+	ld	c,11
+	call	bdos
+	or	a
+	jr	z,main
+	ret
+
+init_siob:
+	ld	a,018h		; channel reset
+	out	(siob_ctrl),a
+
+	ld	a,04h
+	out	(siob_ctrl),a	; wr4 baud settings
+	ld	a,0c4h
+	out	(siob_ctrl),a
+
+	ld	a,03h
+	out	(siob_ctrl),a	; rx enable
+	ld	a,0c1h
+	out	(siob_ctrl),a
+
+	ld	a,05h
+	out	(siob_ctrl),a	; tx settings
+	ld	a,0eah
+	out	(siob_ctrl),a
+
+	ret
+
+init_lcd:
+	ld	a,38h
+	out	(lcd_ctrl),a	; function 8 bit, 2 lines, 5x8 dot font
+	call	lcd_delay
+	ld	a,0ch
+	out	(lcd_ctrl),a	; display on, cursor off, no blink
+	call	lcd_delay
+	ld	a,01h
+	out	(lcd_ctrl),a	; clear display
+
+	ret
+
+lcd_delay:
+	ld	bc,500
+delay1:
+	dec	bc
+	ld	a,b
+	or	c
+	jr	nz,delay1
+	ret
+
+read_char_b:
+wait:
+	in	a,(siob_ctrl)
+	bit	0,a
+	jr	z,wait
+
+	in	a,(siob_data)
+	ret
+
+print_char_to_lcd:
+	cp	a,0dh	; carriage return
+	jr	z,lcd_done
+	cp	a,0ah	; new line
+	jr	z,lcd_done
+	cp	a,054h	; T character
+	call	z,move_to_tempaddr
+	cp	a,050h	; P character
+	call	z,move_to_presaddr
+	cp	a,048h	; H character
+	call	z,move_to_humidaddr
+	out	(lcd_data),a
+lcd_done:
+	ret	
+
+print_str_to_lcd:	; place memory address in hl first
+	ld	a,(hl)
+	or	a
+	jr	z,print_done
+
+	out	(lcd_data),a
+	call	lcd_delay
+	inc	hl
+	jr	print_str_to_lcd
+print_done:
+	ret
+
+move_to_tempaddr:
+	ld	c,a
+	ld	a,85h
+	out	(lcd_ctrl),a
+	ld	a,c
+	ret
+
+move_to_presaddr:
+	ld	a,0c1h
+	out	(lcd_ctrl),a
+	ret
+
+move_to_humidaddr:
+	ld	a,99h
+	out	(lcd_ctrl),a
+	ret
+
+print_char:
+	ld	e,a
+	ld	c,conout
+	call	bdos
+	ret
+
+clabel: DB 'degree C',0
+plabel: DB 'pascal',0
+hlabel: DB '% RH',0
+
+	end	start
+