spi_software: Implementation of software spi

Signed-off-by: Matt Janus <FragginRight@variabl.es>
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

4 files changed, 128 insertions, 5 deletions

diff --git a/src/Makefile b/src/Makefile
index 02386d9c..546dc0a5 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -7,4 +7,4 @@ src-$(CONFIG_HAVE_GPIO_SPI) += spicmds.c thermocouple.c
 src-$(CONFIG_HAVE_GPIO_I2C) += i2ccmds.c
 src-$(CONFIG_HAVE_GPIO_HARD_PWM) += pwmcmds.c
 src-$(CONFIG_HAVE_GPIO_BITBANGING) += lcd_st7920.c lcd_hd44780.c buttons.c \
-    tmcuart.c
+    tmcuart.c spi_software.c
diff --git a/src/spi_software.c b/src/spi_software.c
new file mode 100644
index 00000000..385b4f87
--- /dev/null
+++ b/src/spi_software.c
@@ -0,0 +1,81 @@
+// Software SPI emulation
+//
+// Copyright (C) 2019  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include "board/irq.h" // gpio_out_setup
+#include "board/gpio.h" // gpio_out_setup
+#include "basecmd.h" // oid_alloc
+#include "command.h" // DECL_COMMAND
+#include "sched.h" // sched_shutdown
+
+struct spi_software {
+    struct gpio_out sclk, mosi;
+    struct gpio_in miso;
+    uint8_t mode;
+};
+
+void
+command_config_software_spi(uint32_t *args)
+{
+    uint8_t oid = args[0], sclk_pin = args[1], mosi_pin = args[2];
+    uint8_t miso_pin = args[3], mode = args[4];
+    if (mode > 3)
+        shutdown("Invalid spi mode");
+
+    struct spi_software *spi = oid_alloc(oid, command_config_software_spi
+                                         , sizeof(*spi));
+
+    spi->sclk = gpio_out_setup(sclk_pin, 0);
+    spi->mosi = gpio_out_setup(mosi_pin, 0);
+    spi->miso = gpio_in_setup(miso_pin, 1);
+}
+DECL_COMMAND(command_config_software_spi,
+             "config_software_spi oid=%c sclk_pin=%u mosi_pin=%u miso_pin=%u"
+             " mode=%u rate=%u");
+
+struct spi_software *
+spi_software_oid_lookup(uint8_t oid)
+{
+    return oid_lookup(oid, command_config_software_spi);
+}
+
+void
+spi_software_prepare(struct spi_software *ss)
+{
+    gpio_out_write(ss->sclk, ss->mode < 2 ? 0 : 1);
+}
+
+void
+spi_software_transfer(struct spi_software *ss, uint8_t receive_data
+                      , uint8_t len, uint8_t *data)
+{
+    while (len--) {
+        uint8_t outbuf = *data;
+        uint8_t inbuf = 0;
+        for (uint_fast8_t i = 0; i < 8; i++) {
+            if (ss->mode & 0x01) {
+                // MODE 1 & 3
+                gpio_out_toggle(ss->sclk);
+                gpio_out_write(ss->mosi, outbuf & 0x80);
+                outbuf <<= 1;
+                gpio_out_toggle(ss->sclk);
+                inbuf <<= 1;
+                inbuf |= gpio_in_read(ss->miso);
+            } else {
+                // MODE 0 & 2
+                gpio_out_write(ss->mosi, outbuf & 0x80);
+                outbuf <<= 1;
+                gpio_out_toggle(ss->sclk);
+                inbuf <<= 1;
+                inbuf |= gpio_in_read(ss->miso);
+                gpio_out_toggle(ss->sclk);
+            }
+        }
+
+        if (receive_data)
+            *data = inbuf;
+        data++;
+    }
+}
diff --git a/src/spi_software.h b/src/spi_software.h
new file mode 100644
index 00000000..549866f2
--- /dev/null
+++ b/src/spi_software.h
@@ -0,0 +1,11 @@
+#ifndef __SPI_SOFTWARE_H
+#define __SPI_SOFTWARE_H
+
+#include <stdint.h> // uint8_t
+
+struct spi_software *spi_software_oid_lookup(uint8_t oid);
+void spi_software_prepare(struct spi_software *ss);
+void spi_software_transfer(struct spi_software *ss, uint8_t receive_data
+                           , uint8_t len, uint8_t *data);
+
+#endif // spi_software.h
diff --git a/src/spicmds.c b/src/spicmds.c
index 0017c56b..99e3b3a6 100644
--- a/src/spicmds.c
+++ b/src/spicmds.c
@@ -5,14 +5,19 @@
 // This file may be distributed under the terms of the GNU GPLv3 license.
 
 #include <string.h> // memcpy
+#include "autoconf.h" // CONFIG_HAVE_GPIO_BITBANGING
 #include "board/gpio.h" // gpio_out_write
 #include "basecmd.h" // oid_alloc
 #include "command.h" // DECL_COMMAND
 #include "sched.h" // DECL_SHUTDOWN
+#include "spi_software.h" // spi_software_setup
 #include "spicmds.h" // spidev_transfer
 
 struct spidev_s {
-    struct spi_config spi_config;
+    union {
+        struct spi_config spi_config;
+        struct spi_software *spi_software;
+    };
     struct gpio_out pin;
     uint8_t flags;
     uint8_t shutdown_msg_len;
@@ -20,7 +25,7 @@ struct spidev_s {
 };
 
 enum {
-    SF_HAVE_PIN = 1,
+    SF_HAVE_PIN = 1, SF_SOFTWARE = 2,
 };
 
 void
@@ -58,6 +63,26 @@ DECL_COMMAND(command_config_spi_without_cs,
              "config_spi_without_cs oid=%c bus=%u mode=%u rate=%u"
              " shutdown_msg=%*s");
 
+void
+command_config_spi_from_software(uint32_t *args)
+{
+    uint8_t shutdown_msg_len = args[3];
+    struct spi_software *sspi = spi_software_oid_lookup(args[1]);
+    struct spidev_s *spi = oid_alloc(args[0], command_config_spi
+                                     , sizeof(*spi) + shutdown_msg_len);
+    spi->pin = gpio_out_setup(args[2], 1);
+    spi->flags = SF_HAVE_PIN | SF_SOFTWARE;
+    spi->spi_software = sspi;
+    spi->shutdown_msg_len = shutdown_msg_len;
+    uint8_t *shutdown_msg = (void*)(size_t)args[4];
+    memcpy(spi->shutdown_msg, shutdown_msg, shutdown_msg_len);
+}
+#if CONFIG_HAVE_GPIO_BITBANGING
+DECL_COMMAND(command_config_spi_from_software,
+             "config_spi_from_software oid=%c sw_oid=%u pin=%u"
+             " shutdown_msg=%*s");
+#endif
+
 struct spidev_s *
 spidev_oid_lookup(uint8_t oid)
 {
@@ -68,12 +93,18 @@ void
 spidev_transfer(struct spidev_s *spi, uint8_t receive_data
                 , uint8_t data_len, uint8_t *data)
 {
-    spi_prepare(spi->spi_config);
+    if (CONFIG_HAVE_GPIO_BITBANGING && spi->flags & SF_SOFTWARE)
+        spi_software_prepare(spi->spi_software);
+    else
+        spi_prepare(spi->spi_config);
 
     if (spi->flags & SF_HAVE_PIN)
         gpio_out_write(spi->pin, 0);
 
-    spi_transfer(spi->spi_config, receive_data, data_len, data);
+    if (CONFIG_HAVE_GPIO_BITBANGING && spi->flags & SF_SOFTWARE)
+        spi_software_transfer(spi->spi_software, receive_data, data_len, data);
+    else
+        spi_transfer(spi->spi_config, receive_data, data_len, data);
 
     if (spi->flags & SF_HAVE_PIN)
         gpio_out_write(spi->pin, 1);