detpic/i2clib.asm

   1 ;######################################################################
   2 ; i2clib.inc - I2C LIBRARY - IMPLEMENTATION
   3 ;
   4 ; See i2clib.asm for documentation of the interface to this file.
   5
   6  include /usr/share/gputils/header/p18f458.inc
   7  radix dec
   8  include ../iwjpictest/insn-aliases.inc
   9
  10 ;============================================================
  11 ; COMMON ADMINISTRATIVE ROUTINES and VARIABLES
  12
  13                 udata_acs
  14
  15 sspstat         res     1
  16 sspcon1         res     1
  17 sspcon2         res     1
  18
  19 st      res     1 ; bitmask, bit set in visible states:
  20                   ;    master                          slave
  21 st_reading      equ 0 ; Reading-*                       Transmitting
  22 st_writing      equ 1 ; Writing-*                       [Idle-going-]Receiving
  23 st_subsequent   equ 2 ;                                 Receiving
  24 st_working      equ 3 ; Writing-*,Reading-Busy,Stopping
  25 st_starting     equ 4 ; Writing-Setup,Reading-Busy
  26
  27                 code
  28
  29 ;----------
  30 slave2addr
  31 ; computes slave address in form suitable for use in i2c controller
  32 ; actual i2c slave address is (slave number) + 0b0001000
  33 ;       W               slave number            i2c address * 2
  34                 add_lw  0b0001000
  35                 rlc_w
  36                 return
  37
  38 ;----------
  39 check_wcolsspov
  40                 mov_fw  SSPCON1
  41                 mov_wf  ssp
  42                 and_lw  0xc0 ; WCOL,SSPOV
  43                 bra_z   intr_wcolsspov
  44                 return
  45
  46 ;----------
  47 intr_wcolsspov
  48                 panic   morse_SV
  49
  50 ;======================================================================
  51 ; MASTER
  52
  53 ;----------
  54 i2cm_init
  55                 mov_lw  100-1   ; baud rate = Fosc/(4*(SSPADD+1))
  56                 mov_wf  SSPADD  ; Fosc=20MHz, so SSPADD==99 means 50kbit/s
  57                 mov_lw  0x08    ; !SSPEN, Master mode
  58                 mov_wf  SSPCON1
  59                 clr_f   SSPCON2 ; nothing going
  60                 mov_lw  0x80    ; SMP(noslew), !CKE(!smbus)
  61                 bra     init_enable
  62
  63 ;----------
  64 i2cm_write_start
  65 ;                               At call         On return
  66 ;   State                       Idle            Writing-Setup
  67 ;   W                           slave number    any
  68                 tst_f_ifnz st
  69                 bra     m_bad_write_start
  70                 bs_f    st, st_writing
  71 m_start
  72                 bs_f    st, st_starting
  73                 bs_f    SSPCON2, SEN
  74                 return
  75
  76 ;----------
  77 m_bad_write_start
  78                 panic   morse_SPW
  79
  80 ;----------
  81 i2cm_interrupt
  82                 ; Do we have a doomy clash ?
  83                 bsr     check_wcolsspov
  84
  85                 ; No ?  Well, then the I2C should be idle now:
  86                 mov_fw  SSPCON2
  87                 mov_wf  ssp
  88                 and_lw  ~0x60 ; ACKSTAT,ACKDT
  89                 bra_nz  m_bad_sspcon2
  90                 ; OK, what's happening;
  91
  92                 bt_f_if0 PIR1, SSPIF
  93                 return
  94                 ; We have an interrupt:
  95
  96                 bt_f_if1 st, st_starting
  97                 bra     m_event_starting
  98                 ; not just done SEN
  99
 100                 fixme
 101
 102 ;----------
 103 m_bad_sspcon2
 104                 panic   morse_SM
 105
 106
 107 ;----------
 108 m_event_starting
 109                 mov_lw  0x88
 110                 bsr     m_check_sspstat
 111
 112
 113 m_check_sspstat
 114 ;       W       expected bit values             any
 115 ; Panics if  (SSPSTAT ^ W) & mask  != 0
 116                 mov_ff  SSPSTAT, ssp
 117
 118
 119 ;======================================================================
 120 ; SLAVE
 121
 122 ;----------
 123 i2cs_init
 124 ;       W               slave number            undefined
 125                 rcall   slave2addr2
 126                 mov_wf  SSPADD
 127                 clr_f   st
 128                 mov_lw  0x16 ; !SSPEN, CKP(release), I2C 7-bit slave no-SP-int
 129                 mov_wf  SSPCON1
 130                 mov_lw  0x01 ; !GCEN, SEN
 131                 mov_wf  SSPCON2
 132                 mov_lw  0x8 ; SMP(noslew), !CKE(!smbus)
 133                 mov_wf  SSPSTAT
 134 ms_init_enable
 135 ; Actually engages the I2C controller, which must already have
 136 ; been set up (all but SSPEN):
 137 ;  SSPADD,SSPCON1,SSPCON2       configured correctly    unchanged
 138 ;       SSPSTAT                 configured correctly    unchanged, except:
 139 ;       SSPSTAT<SSPEN>          0 (disabled)            1 (enabled)
 140 ;       SSPIE                   0 (disabled)            1 (enabled)
 141 ;       TRISB<1,0>              any                     configured for I2C
 142 ;       SSPIP                   any                     configured correctly
 143 ;       GIEL                    0 (disabled)            0 (disabled)
 144                 bs_f    TRISB, 0
 145                 bs_f    TRISB, 1
 146                 bc_f    IPR1, SSPIP
 147                 bs_f    SSPCON1, SSPEN
 148                 bs_f    PIE1, SSPIE
 149                 return
 150
 151 ;========================================
 152 ; SLAVE - INTERRUPT HANDLING
 153
 154 ; In general, we figure out our state and then see what kind of events
 155 ; we were expecting.  Bits we want to check:
 156 ;       80    60    20    10            08    04    02    01
 157 ;       SMP   CKE   D_A   P             S     R_W   UA    BF
 158 ;       set   clr   data? stop          start read? clr   full?
 159 ; (we don't usually mention SMP, CKE and UA below)
 160
 161 ; Some macros:
 162
 163 chkvals_start macro
 164                 mov_fw  ssp
 165 chkval_lastvalue equ 0
 166                 endm
 167
 168 chkval macro value, label
 169                 xor_lw  value ^ chkval_lastvalue
 170  chkval_lastvalue equ value
 171                 bra_z   label
 172                 endm
 173
 174 chkvals_addrrecv macro
 175                 chkval  0x8c, s_event_idle_addrrecvread ; A,!P, S,R,!BF
 176                 chkval  0x89, s_event_idle_addrrecvwrite ; A,!P, S,W,BF
 177                 endm
 178
 179 ;----------
 180 i2cs_interrupt
 181                 bt_f_if0 PIR1, SSPIF
 182                 return
 183                 ; We have an interrupt:
 184
 185 ; Firstly, clear the interrupt flag so that if something else happens
 186 ; while we faff, the interrupt will be regenerated:
 187                 bc_f    PIR1, SSPIF
 188
 189 ; Check that nothing obvious is wrong:
 190                 bsr     check_wcolsspov
 191
 192                 bt_f_if0 st, st_reading
 193                 bra     s_event_reading
 194
 195                 bt_f_if0 st, st_writing
 196                 bra     s_event_writing
 197
 198 s_event_idle
 199                 chkvals_start
 200                 chkvals_addrrecv
 201
 202                 panic   morse_SI
 203
 204 ;========================================
 205 ; SLAVE - READING
 206
 207 ;----------
 208 s_event_idle_addrrecvread
 209                 bs_f    st, st_reading
 210                 call    i2csu_read_begin
 211                 bra     s_events_read_datasend
 212
 213 ;----------
 214 s_event_reading
 215                 chkvals_start
 216                 chkval  0xac, s_event_reading_datasent ; D,!P, S,R,!BF
 217
 218                 ; Whatever is happening, we're done reading now !
 219                 clr_f   st
 220                 call    i2csu_read_done
 221
 222                 chkval  0xa8, s_event_reading_datanack ; D,!P, S,!R,!BF
 223                 ; Or, maybe it was nack and then we were reselected:
 224                 chkvals_addrrecv
 225
 226                 panic   morse_SR
 227
 228 ;----------
 229 s_event_reading_datasent
 230                 call    i2csu_read_another
 231 s_events_reading_datasend
 232                 mov_wf  SSPBUF
 233                 bs_f    SSPCON1, CKP
 234 s_event_reading_datanack
 235                 return
 236
 237 ;========================================
 238 ; SLAVE - WRITING
 239
 240 ;----------
 241 s_event_idle_addrrecvwrite
 242                 bs_f    SSPCON, 3 ; we'll need the Stop interrupt
 243                 bs_f    st, st_writing
 244                 ; well, this is all fine so far, so do carry on:
 245
 246 s_write_slurpbyte
 247 ;       W               any                     byte from master
 248 ;       i2c controller  waiting due to SEN etc  continuing with next byte
 249                 mov_fw  SSPBUF
 250                 bs_f    SSPCON1, CKP
 251                 return
 252
 253 ;----------
 254 s_event_writing
 255                 chkvals_start
 256                 chkval  0xa9, s_event_writing_datarecv ; D,!P, S,W,BF
 257
 258                 ; Well, we're done writing now in any case
 259                 clr_f   st
 260                 bc_f    SSPCON1, 3 ; no Start and Stop interrupts any more
 261                 call    i2csu_write_done
 262
 263                 ; Who knows what might have happened.  We may have
 264                 ; missed a number of S and P due to delay between
 265                 ; clearing SSPIF and SSPM3(s&p-intrs) so we can't be
 266                 ; too picky.
 267
 268                 ; First, the nice cases:
 269                 chkvals_start
 270                 chkvals_addrrecv
 271
 272                 ; Then random junk:
 273                 mov_fw  ssp
 274                 and_lw  0xc7 ; ?D_A, ?P; ?S
 275                 xor_lw  0x80 ; SMP, !CKE, !R_W, !UA, !BF
 276                 bt_f_if1 STATUS, Z
 277                 return
 278
 279                 panic   morse_SW
 280
 281 ;----------
 282 s_event_writing_datarecv
 283                 rcall   s_write_slurpbyte
 284
 285                 bt_f_if1 st, st_subsequent
 286                 goto    i2csu_write_another
 287                 ; not subsequent (yet):
 288
 289                 bs_f    st, st_subsequent
 290                 goto    i2csu_write_begin
 291
 292 ;======================================================================
 293
 294  include i2clib.inc
 295  end