mim 電路圖..... 可以從源代碼分析出來 :
不過他沒交代 1200/2200hz 產生的方法, 不知是不是 pwm 腳, tt 是用四支腳位作 4bit dac--> sine wave 的...
; "mic107c.src" -- interfacing gps (nmea 0183) to pic16c73
; serial communications at 4800 baud (20mhz xtal)
;
; c. wick & w. clement, 5/96
; changes made 10/20/98
;
; changes from "mic107a.src":
; (1) output packets serially (rs232) as well as through ax.25 tones.
device pic16c73a, hs_osc, wdt_on, pwrt_on, protect_on
; device pic16c73, hs_osc, wdt_on, pwrt_on, protect_off
; registers
org 32
.......
.......
; serial eeprom port usage
cs equ portc.5 ; chip select, 93c66 serial eeprom (output)
clk equ portc.4 ; clock, 93c66 serial eeprom (output)
do equ portc.3 ; data out, 93c66 serial eeprom (input)
di equ portc.2 ; data in, 93c66 serial eeprom (output)
; transmitter port usage
holdoff equ porta.4 ; hold-off signal from receiver (input)
ptt equ portc.0 ; push-to-talk (output)
; pwm_out equ portc.1 ; (output)
; serial communications port usage
; out232 equ portc.6 ; (output)
; in232 equ portc.7 ; (input)
; mic encoder equates
ptt_in equ portb.0 ; (input)
; ----------------------------- start of code -----------------------------