drivers/twserial/soft_tws.c

   1 /*
   2  * (C) Copyright 2009
   3  * Detlev Zundel, DENX Software Engineering, dzu@denx.de.
   4  *
   5  * SPDX-License-Identifier:     GPL-2.0+
   6  */
   7
   8 #define TWS_IMPLEMENTATION
   9 #include <common.h>
  10
  11 /*=====================================================================*/
  12 /*                         Public Functions                            */
  13 /*=====================================================================*/
  14
  15 /*-----------------------------------------------------------------------
  16  * Read bits
  17  */
  18 int tws_read(uchar *buffer, int len)
  19 {
  20         int rem = len;
  21         uchar accu, shift;
  22
  23         debug("tws_read: buffer %p len %d\n", buffer, len);
  24
  25         /* Configure the data pin for input */
  26         tws_data_config_output(0);
  27
  28         /* Disable WR, i.e. setup a read */
  29         tws_wr(0);
  30         udelay(1);
  31
  32         /* Rise CE */
  33         tws_ce(1);
  34         udelay(1);
  35
  36         for (; rem > 0; ) {
  37                 for (shift = 0, accu = 0;
  38                      (rem > 0) && (shift < 8);
  39                      rem--, shift++) {
  40                         tws_clk(1);
  41                         udelay(10);
  42                         accu |= (tws_data_read() << shift); /* LSB first */
  43                         tws_clk(0);
  44                         udelay(10);
  45                 }
  46                 *buffer++ = accu;
  47         }
  48
  49         /* Lower CE */
  50         tws_ce(0);
  51
  52         return len - rem;
  53 }
  54
  55
  56 /*-----------------------------------------------------------------------
  57  * Write bits
  58  */
  59 int tws_write(uchar *buffer, int len)
  60 {
  61         int rem = len;
  62         uchar accu, shift;
  63
  64         debug("tws_write: buffer %p len %d\n", buffer, len);
  65
  66         /* Configure the data pin for output */
  67         tws_data_config_output(1);
  68
  69         /* Enable WR, i.e. setup a write */
  70         tws_wr(1);
  71         udelay(1);
  72
  73         /* Rise CE */
  74         tws_ce(1);
  75         udelay(1);
  76
  77         for (; rem > 0; ) {
  78                 for (shift = 0, accu = *buffer++;
  79                      (rem > 0) && (shift < 8);
  80                      rem--, shift++) {
  81                         tws_data(accu & 0x01); /* LSB first */
  82                         tws_clk(1);
  83                         udelay(10);
  84                         tws_clk(0);
  85                         udelay(10);
  86                         accu >>= 1;
  87                 }
  88         }
  89
  90         /* Lower CE */
  91         tws_ce(0);
  92
  93         return len - rem;
  94 }