Added spi/spi_master_slave.

Michael Stoops · Wren6991 · commit dea81ae73dea · 2021-06-02T19:47:43.000+01:00
diff --git a/README.md b/README.md
@@ -9,7 +9,7 @@ on getting up and running.
 
 App|Description | Link to prebuilt UF2
 ---|---|---
-[hello_serial](hello_world/serial) | The obligatory Hello World program for Pico (Output over serial version) | 
+[hello_serial](hello_world/serial) | The obligatory Hello World program for Pico (Output over serial version) |
 [hello_usb](hello_world/usb) | The obligatory Hello World program for Pico (Output over USB version) | https://rptl.io/pico-hello-usb
 [blink](blink) | Blink an LED on and off. | https://rptl.io/pico-blink
 
@@ -43,7 +43,6 @@ App|Description
 [control_blocks](dma/control_blocks)| Build a control block list, to program a longer sequence of DMA transfers to the UART.
 [channel_irq](dma/channel_irq)| Use an IRQ handler to reconfigure a DMA channel, in order to continuously drive data through a PIO state machine.
 
-
 ### Flash
 
 App|Description
@@ -70,7 +69,6 @@ App|Description
 ---|---
 [hello_divider](divider) | Show how to directly access the hardware integer dividers, in case AEABI injection is disabled.
 
-
 ### I2C
 
 App|Description
@@ -90,7 +88,7 @@ App|Description
 App|Description
 ---|---
 [hello_multicore](multicore/hello_multicore) | Launch a function on the second core, printf some messages on each core, and pass data back and forth through the mailbox FIFOs.
-[multicore_fifo_irqs](multicore/multicore_fifo_irqs) | On each core, register and interrupt handler for the mailbox FIFOs. Show how the interrupt fires when that core receives a message. 
+[multicore_fifo_irqs](multicore/multicore_fifo_irqs) | On each core, register and interrupt handler for the mailbox FIFOs. Show how the interrupt fires when that core receives a message.
 [multicore_runner](multicore/multicore_runner) | Set up the second core to accept, and run, any function pointer pushed into its mailbox FIFO. Push in a few pieces of code and get answers back.
 
 ### Pico Board
@@ -151,6 +149,7 @@ App|Description
 [mpu9250_spi](spi/mpu9250_spi) | Attach a MPU9250 accelerometer/gyoscope via SPI.
 [spi_dma](spi/spi_dma) | Use DMA to transfer data both to and from the SPI simultaneously. The SPI is configured for loopback.
 [spi_flash](spi/spi_flash) | Erase, program and read a serial flash device attached to one of the SPI controllers.
+[spi_master_slave](spi/spi_master_slave) | Demonstrate SPI communication as master and slave.
 
 ### System
 
@@ -159,6 +158,7 @@ App|Description
 [hello_double_tap](system/hello_double_tap) | An LED blink with the `pico_bootsel_via_double_reset` library linked. This enters the USB bootloader when it detects the system being reset twice in quick succession, which is useful for boards with a reset button but no BOOTSEL button.
 [narrow_io_write](system/narrow_io_write) | Demonstrate the effects of 8-bit and 16-bit writes on a 32-bit IO register.
 [unique_board_id](system/unique_board_id) | Read the 64 bit unique ID from external flash, which serves as a unique identifier for the board.
+
 ### Timer
 
 App|Description
diff --git a/spi/CMakeLists.txt b/spi/CMakeLists.txt
@@ -3,4 +3,5 @@ if (NOT PICO_NO_HARDWARE)
     add_subdirectory(mpu9250_spi)
     add_subdirectory(bme280_spi)
     add_subdirectory(spi_dma)
+    add_subdirectory(spi_master_slave)
 endif ()
diff --git a/spi/spi_master_slave/CMakeLists.txt b/spi/spi_master_slave/CMakeLists.txt
@@ -0,0 +1,4 @@
+if (NOT PICO_NO_HARDWARE)
+    add_subdirectory(spi_master)
+    add_subdirectory(spi_slave)
+endif ()
diff --git a/spi/spi_master_slave/README.md b/spi/spi_master_slave/README.md
@@ -0,0 +1,98 @@
+# spi_master and spi_slave
+
+These examples demonstrate using the PL022 hardware SPI module both as master and slave. Each program is meant to be written to its own RP2040 module.
+
+The two modules are meant to be wired together as follows. The RP2040 pin numbers are those on the RP2040 chip itself. The Pico pin numbers are mapped to the pads on the Raspberry Pi Pico board:
+
+| Function | Master pin (RP2040) | Slave pin (RP2040) | Master pin (Pico) | Slave pin (Pico) |
+|-|-|-|-|-|
+| MOSI | DO0  | DI0  | 25 | 21 |
+| SCLK | SCK0 | SCK0 | 24 | 24 |
+| GND  | GND  | GND  | 23 | 23 |
+| CS   | CS0  | CS0  | 22 | 22 |
+| MISO | DI0  | DO0  | 21 | 25 |
+
+You will also want to power the boards and at least watch the master's output using a serial terminal.
+
+It is possible to execute one of the programs without the other, but the master will receive no response, as there is no slave listening. The slave program will initialize, but will neither transmit nor receive anything because there will be no clock pulses.
+
+## Outputs
+
+The slave will be confused if it starts while the master is transmitting. The easiest solution is to stop both, start the slave first, the master second.
+
+The master should output the following:
+
+```
+SPI master example
+SPI master initialised.
+The following buffer will be written to MOSI endlessly.
+00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
+10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
+20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f
+30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f
+40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f
+50 51 52 53 54 55 56 57 58 59 5a 5b 5c 5d 5e 5f
+60 61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f
+70 71 72 73 74 75 76 77 78 79 7a 7b 7c 7d 7e 7f
+80 81 82 83 84 85 86 87 88 89 8a 8b 8c 8d 8e 8f
+90 91 92 93 94 95 96 97 98 99 9a 9b 9c 9d 9e 9f
+a0 a1 a2 a3 a4 a5 a6 a7 a8 a9 aa ab ac ad ae af
+b0 b1 b2 b3 b4 b5 b6 b7 b8 b9 ba bb bc bd be bf
+c0 c1 c2 c3 c4 c5 c6 c7 c8 c9 ca cb cc cd ce cf
+d0 d1 d2 d3 d4 d5 d6 d7 d8 d9 da db dc dd de df
+e0 e1 e2 e3 e4 e5 e6 e7 e8 e9 ea eb ec ed ee ef
+f0 f1 f2 f3 f4 f5 f6 f7 f8 f9 fa fb fc fd fe ff
+Read the following from MISO, page 0:
+ff fe fd fc fb fa f9 f8 f7 f6 f5 f4 f3 f2 f1 f0
+ef ee ed ec eb ea e9 e8 e7 e6 e5 e4 e3 e2 e1 e0
+df de dd dc db da d9 d8 d7 d6 d5 d4 d3 d2 d1 d0
+cf ce cd cc cb ca c9 c8 c7 c6 c5 c4 c3 c2 c1 c0
+bf be bd bc bb ba b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
+af ae ad ac ab aa a9 a8 a7 a6 a5 a4 a3 a2 a1 a0
+9f 9e 9d 9c 9b 9a 99 98 97 96 95 94 93 92 91 90
+8f 8e 8d 8c 8b 8a 89 88 87 86 85 84 83 82 81 80
+7f 7e 7d 7c 7b 7a 79 78 77 76 75 74 73 72 71 70
+6f 6e 6d 6c 6b 6a 69 68 67 66 65 64 63 62 61 60
+5f 5e 5d 5c 5b 5a 59 58 57 56 55 54 53 52 51 50
+4f 4e 4d 4c 4b 4a 49 48 47 46 45 44 43 42 41 40
+3f 3e 3d 3c 3b 3a 39 38 37 36 35 34 33 32 31 30
+2f 2e 2d 2c 2b 2a 29 28 27 26 25 24 23 22 21 20
+1f 1e 1d 1c 1b 1a 19 18 17 16 15 14 13 12 11 10
+0f 0e 0d 0c 0b 0a 09 08 07 06 05 04 03 02 01 00
+```
+
+Additional pages follow, all containing the same content.
+
+The slave should output the following:
+
+```
+SPI slave example
+SPI slave initialised.
+When reading from MOSI, the following buffer will be written to MISO:
+ff fe fd fc fb fa f9 f8 f7 f6 f5 f4 f3 f2 f1 f0
+ef ee ed ec eb ea e9 e8 e7 e6 e5 e4 e3 e2 e1 e0
+df de dd dc db da d9 d8 d7 d6 d5 d4 d3 d2 d1 d0
+cf ce cd cc cb ca c9 c8 c7 c6 c5 c4 c3 c2 c1 c0
+bf be bd bc bb ba b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
+af ae ad ac ab aa a9 a8 a7 a6 a5 a4 a3 a2 a1 a0
+9f 9e 9d 9c 9b 9a 99 98 97 96 95 94 93 92 91 90
+8f 8e 8d 8c 8b 8a 89 88 87 86 85 84 83 82 81 80
+7f 7e 7d 7c 7b 7a 79 78 77 76 75 74 73 72 71 70
+6f 6e 6d 6c 6b 6a 69 68 67 66 65 64 63 62 61 60
+5f 5e 5d 5c 5b 5a 59 58 57 56 55 54 53 52 51 50
+4f 4e 4d 4c 4b 4a 49 48 47 46 45 44 43 42 41 40
+3f 3e 3d 3c 3b 3a 39 38 37 36 35 34 33 32 31 30
+2f 2e 2d 2c 2b 2a 29 28 27 26 25 24 23 22 21 20
+1f 1e 1d 1c 1b 1a 19 18 17 16 15 14 13 12 11 10
+0f 0e 0d 0c 0b 0a 09 08 07 06 05 04 03 02 01 00
+```
+
+The slave doesn't write anything else to the console.
+
+## Electrical signals
+
+The communication looks like this when seen through a logic analyzer.
+
+![spi_master_slave.png](spi_master_slave.png)
+
+Original [data file](spi_master_slave.logicdata) is included.
diff --git a/spi/spi_master_slave/spi_master/CMakeLists.txt b/spi/spi_master_slave/spi_master/CMakeLists.txt
@@ -0,0 +1,12 @@
+add_executable(spi_master
+        spi_master.c
+        )
+
+# Pull in basic dependencies
+target_link_libraries(spi_master pico_stdlib hardware_spi)
+
+# create map/bin/hex file etc.
+pico_add_extra_outputs(spi_master)
+
+# add url via pico_set_program_url
+example_auto_set_url(spi_master)
diff --git a/spi/spi_master_slave/spi_master/spi_master.c b/spi/spi_master_slave/spi_master/spi_master.c
@@ -0,0 +1,72 @@
+/**
+ * Copyright (c) 2021 Michael Stoops. All rights reserved.
+ * Portions copyright (c) 2021 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+// Example of an SPI bus master using the PL022 SPI interface
+
+#include <stdio.h>
+#include "pico/stdlib.h"
+#include "pico/binary_info.h"
+#include "hardware/spi.h"
+
+#define BUF_LEN         0x100
+
+void printbuf(uint8_t buf[], size_t len) {
+    int i;
+    for (i = 0; i < len; ++i) {
+        if (i % 16 == 15)
+            printf("%02x\n", buf[i]);
+        else
+            printf("%02x ", buf[i]);
+    }
+
+    // append trailing newline if there isn't one
+    if (i % 16) {
+        putchar('\n');
+    }
+}
+
+int main() {
+    // Enable UART so we can print
+    stdio_init_all();
+#if !defined(spi_default) || !defined(PICO_DEFAULT_SPI_SCK_PIN) || !defined(PICO_DEFAULT_SPI_TX_PIN) || !defined(PICO_DEFAULT_SPI_RX_PIN) || !defined(PICO_DEFAULT_SPI_CSN_PIN)
+#warning spi/spi_master example requires a board with SPI pins
+    puts("Default SPI pins were not defined");
+#else
+
+    printf("SPI master example\n");
+
+    // Enable SPI 0 at 1 KHz and connect to GPIOs
+    spi_init(spi_default, 1000);
+    gpio_set_function(PICO_DEFAULT_SPI_RX_PIN, GPIO_FUNC_SPI);
+    gpio_set_function(PICO_DEFAULT_SPI_SCK_PIN, GPIO_FUNC_SPI);
+    gpio_set_function(PICO_DEFAULT_SPI_TX_PIN, GPIO_FUNC_SPI);
+    gpio_set_function(PICO_DEFAULT_SPI_CSN_PIN, GPIO_FUNC_SPI);
+    // Make the SPI pins available to picotool
+    bi_decl(bi_4pins_with_func(PICO_DEFAULT_SPI_RX_PIN, PICO_DEFAULT_SPI_TX_PIN, PICO_DEFAULT_SPI_SCK_PIN, PICO_DEFAULT_SPI_CSN_PIN, GPIO_FUNC_SPI));
+
+    printf("SPI master initialised.\n");
+
+    uint8_t out_buf[BUF_LEN], in_buf[BUF_LEN];
+
+    // Initialize output buffer
+    for (size_t i = 0; i < BUF_LEN; ++i) {
+        out_buf[i] = i;
+    }
+    
+    printf("The following buffer will be written to MOSI endlessly.\n");
+    printbuf(out_buf, BUF_LEN);
+
+    for (size_t i = 0; true; ++i) {
+        // Write the output buffer to MOSI, and at the same time read from MISO.
+        spi_write_read_blocking(spi_default, out_buf, in_buf, BUF_LEN);
+
+        // Write to stdio whatever came in on the MISO line.
+        printf("Read the following from MISO, page %d:\n", i);
+        printbuf(in_buf, BUF_LEN);
+    }
+#endif
+}
diff --git a/spi/spi_master_slave/spi_master_slave.logicdata b/spi/spi_master_slave/spi_master_slave.logicdata
diff --git a/spi/spi_master_slave/spi_master_slave.png b/spi/spi_master_slave/spi_master_slave.png
diff --git a/spi/spi_master_slave/spi_slave/CMakeLists.txt b/spi/spi_master_slave/spi_slave/CMakeLists.txt
@@ -0,0 +1,12 @@
+add_executable(spi_slave
+        spi_slave.c
+        )
+
+# Pull in basic dependencies
+target_link_libraries(spi_slave pico_stdlib hardware_spi)
+
+# create map/bin/hex file etc.
+pico_add_extra_outputs(spi_slave)
+
+# add url via pico_set_program_url
+example_auto_set_url(spi_slave)
diff --git a/spi/spi_master_slave/spi_slave/spi_slave.c b/spi/spi_master_slave/spi_slave/spi_slave.c
@@ -0,0 +1,74 @@
+/**
+ * Copyright (c) 2021 Michael Stoops. All rights reserved.
+ * Portions copyright (c) 2021 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+// Example of an SPI bus slave using the PL022 SPI interface
+
+#include <stdio.h>
+#include <string.h>
+#include "pico/stdlib.h"
+#include "pico/binary_info.h"
+#include "hardware/spi.h"
+
+#define BUF_LEN         0x100
+
+void printbuf(uint8_t buf[], size_t len) {
+    int i;
+    for (i = 0; i < len; ++i) {
+        if (i % 16 == 15)
+            printf("%02x\n", buf[i]);
+        else
+            printf("%02x ", buf[i]);
+    }
+
+    // append trailing newline if there isn't one
+    if (i % 16) {
+        putchar('\n');
+    }
+}
+
+
+int main() {
+    // Enable UART so we can print
+    stdio_init_all();
+#if !defined(spi_default) || !defined(PICO_DEFAULT_SPI_SCK_PIN) || !defined(PICO_DEFAULT_SPI_TX_PIN) || !defined(PICO_DEFAULT_SPI_RX_PIN) || !defined(PICO_DEFAULT_SPI_CSN_PIN)
+#warning spi/spi_slave example requires a board with SPI pins
+    puts("Default SPI pins were not defined");
+#else
+
+    printf("SPI slave example\n");
+
+    // Enable SPI 0 at 1 KHz and connect to GPIOs
+    spi_init(spi_default, 1000);
+    spi_set_slave(spi_default, true);
+    gpio_set_function(PICO_DEFAULT_SPI_RX_PIN, GPIO_FUNC_SPI);
+    gpio_set_function(PICO_DEFAULT_SPI_SCK_PIN, GPIO_FUNC_SPI);
+    gpio_set_function(PICO_DEFAULT_SPI_TX_PIN, GPIO_FUNC_SPI);
+    gpio_set_function(PICO_DEFAULT_SPI_CSN_PIN, GPIO_FUNC_SPI);
+    // Make the SPI pins available to picotool
+    bi_decl(bi_4pins_with_func(PICO_DEFAULT_SPI_RX_PIN, PICO_DEFAULT_SPI_TX_PIN, PICO_DEFAULT_SPI_SCK_PIN, PICO_DEFAULT_SPI_CSN_PIN, GPIO_FUNC_SPI));
+
+    printf("SPI slave initialised.\n");
+
+    uint8_t out_buf[BUF_LEN], in_buf[BUF_LEN];
+
+    // Initialize output buffer
+    for (size_t i = 0; i < BUF_LEN; ++i) {
+        // bit-inverted from i. The values should be: {0xff, 0xfe, 0xfd...}
+        out_buf[i] = ~i;
+    }
+
+    printf("When reading from MOSI, the following buffer will be written to MISO:\n");
+    printbuf(out_buf, BUF_LEN);
+    
+    for (size_t i = 0; true; ++i) {
+        // Write the output buffer to MISO, and at the same time read from MOSI.
+        spi_write_read_blocking(spi_default, out_buf, in_buf, BUF_LEN);
+
+        // The slave doesn't print the buffer. It can't afford to ignore the SPI bus while writing to stdio.
+    }
+#endif
+}
