From db09cf20e709a1aafd1d91a5de99e4dcda7927a4 Mon Sep 17 00:00:00 2001 From: Nicolas Schodet Date: Mon, 29 Nov 2010 23:07:51 +0100 Subject: digital/avr/modules/twi: implement software master, closes #141 --- digital/avr/modules/twi/twi_soft.avr.c | 240 +++++++++++++++++++++++++++++++++ 1 file changed, 240 insertions(+) create mode 100644 digital/avr/modules/twi/twi_soft.avr.c (limited to 'digital/avr/modules/twi/twi_soft.avr.c') diff --git a/digital/avr/modules/twi/twi_soft.avr.c b/digital/avr/modules/twi/twi_soft.avr.c new file mode 100644 index 00000000..b673d5be --- /dev/null +++ b/digital/avr/modules/twi/twi_soft.avr.c @@ -0,0 +1,240 @@ +/* twi_soft.avr.c - Software master implementation. */ +/* avr.twi - TWI AVR module. {{{ + * + * Copyright (C) 2010 Nicolas Schodet + * + * APBTeam: + * Web: http://apbteam.org/ + * Email: team AT apbteam DOT org + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + * + * }}} */ +#include "common.h" +#include "twi.h" + +#if TWI_DRIVER == TWI_DRIVER_SOFT + +# include "modules/utils/utils.h" +# include "io.h" + +# if AC_TWI_SLAVE_ENABLE +# error "twi: slave mode not supported by software driver" +# endif +# if AC_TWI_NO_INTERRUPT +# warning "twi: no interrupt anyway" +# endif + +/* Define IO shortcuts. */ +# define SDA_IO AC_TWI_SOFT_SDA_IO +# define SCL_IO AC_TWI_SOFT_SCL_IO + +# if AC_TWI_PULL_UP +# define SDA_0 do { IO_CLR (SDA_IO); IO_OUTPUT (SDA_IO); } while (0) +# define SDA_1 do { IO_INPUT (SDA_IO); IO_SET (SDA_IO); } while (0) +# define SCL_0 do { IO_CLR (SCL_IO); IO_OUTPUT (SCL_IO); } while (0) +# define SCL_1 do { IO_INPUT (SCL_IO); IO_SET (SCL_IO); } while (0) +# else +# define SDA_0 do { IO_OUTPUT (SDA_IO); } while (0) +# define SDA_1 do { IO_INPUT (SDA_IO); } while (0) +# define SCL_0 do { IO_OUTPUT (SCL_IO); } while (0) +# define SCL_1 do { IO_INPUT (SCL_IO); } while (0) +# endif + +# if AC_TWI_MASTER_ENABLE + +/** Current master status. */ +uint8_t twi_master_current_status; + +# endif + +void +twi_init (uint8_t addr) +{ +#if AC_TWI_PULL_UP + SDA_1; + SCL_1; +#else + IO_CLR (SDA_IO); + SDA_1; + IO_CLR (SCL_IO); + SCL_1; +#endif +} + +void +twi_uninit (void) +{ + /* Keep pull-up. */ +} + +# if AC_TWI_MASTER_ENABLE + +/** Wait a half bit period. */ +static void +twi_delay (void) +{ + utils_delay (0.5 / AC_TWI_FREQ); +} + +/** Wait until SCL is high to enable clock stretching. */ +static inline void +twi_wait_scl (void) +{ + while (!IO_GET (SCL_IO)) + ; +} + +/** Send start condition. */ +static void +twi_master_send_start (void) +{ + SDA_0; + twi_delay (); + SCL_0; + twi_delay (); +} + +/** Send stop condition. */ +static void +twi_master_send_stop (void) +{ + SDA_0; + twi_delay (); + SCL_1; + twi_wait_scl (); + twi_delay (); + SDA_1; + twi_delay (); +} + +/** Send one bit. */ +static void +twi_master_send_bit (uint8_t bit) +{ + if (bit) + SDA_1; + else + SDA_0; + twi_delay (); + SCL_1; + twi_wait_scl (); + twi_delay (); + SCL_0; +} + +/** Receive one bit. */ +static uint8_t +twi_master_recv_bit (void) +{ + SDA_1; + twi_delay (); + SCL_1; + twi_wait_scl (); + uint8_t bit = IO_GET (SDA_IO) ? 1 : 0; + twi_delay (); + SCL_0; + return bit; +} + +/** Send one byte, return the received nack bit. */ +static uint8_t +twi_master_send_byte (uint8_t b) +{ + uint8_t i; + for (i = 8; i; i--) + { + twi_master_send_bit (b & 0x80); + b <<= 1; + } + return twi_master_recv_bit (); +} + +/** Receive one byte, send the nack bit. */ +static uint8_t +twi_master_recv_byte (uint8_t nack) +{ + uint8_t i, b; + b = 0; + for (i = 8; i; i--) + { + b <<= 1; + b |= twi_master_recv_bit (); + } + twi_master_send_bit (nack); + return b; +} + +void +twi_master_send (uint8_t addr, const uint8_t *buffer, uint8_t size) +{ + uint8_t nack, sent = 0; + /* Start. */ + twi_master_send_start (); + /* Send SLA+W. */ + nack = twi_master_send_byte (addr | 0); + /* Send data. */ + for (; !nack && sent < size; sent++) + nack = twi_master_send_byte (buffer[sent]); + /* Stop. */ + twi_master_send_stop (); + /* Update status, there is no background task. */ + twi_master_current_status = sent; + /* If defined, call master done callback. */ +#ifdef AC_TWI_MASTER_DONE + AC_TWI_MASTER_DONE (); +#endif +} + +void +twi_master_recv (uint8_t addr, uint8_t *buffer, uint8_t size) +{ + uint8_t nack, recv = 0; + /* Start. */ + twi_master_send_start (); + /* Send SLA+R. */ + nack = twi_master_send_byte (addr | 1); + if (!nack) + { + /* Receive data, send nack in last byte. */ + for (; recv < size; recv++) + buffer[recv] = twi_master_recv_byte (recv == size - 1 ? 1 : 0); + } + /* Stop. */ + twi_master_send_stop (); + /* Update status, there is no background task. */ + twi_master_current_status = recv; + /* If defined, call master done callback. */ +#ifdef AC_TWI_MASTER_DONE + AC_TWI_MASTER_DONE (); +#endif +} + +uint8_t +twi_master_status (void) +{ + return twi_master_current_status; +} + +uint8_t +twi_master_wait (void) +{ + /* No background task, nothing to wait. */ + return twi_master_current_status; +} + +# endif /* AC_TWI_MASTER_ENABLE */ + +#endif /* TWI_DRIVER == TWI_DRIVER_SOFT */ -- cgit v1.2.3