SPIM3 buffer must be in first 64kB of RAM

13 files changed, 115 insertions, 100 deletions

diff --git a/ports/nrf/boards/arduino_nano_33_ble/mpconfigboard.mk b/ports/nrf/boards/arduino_nano_33_ble/mpconfigboard.mk
index d5e38c5b7..9b16834b5 100644
--- a/ports/nrf/boards/arduino_nano_33_ble/mpconfigboard.mk
+++ b/ports/nrf/boards/arduino_nano_33_ble/mpconfigboard.mk
@@ -6,10 +6,3 @@ USB_MANUFACTURER = "Arduino"
 MCU_CHIP = nrf52840
 
 INTERNAL_FLASH_FILESYSTEM = 1
-
-# Allocate two, not just one I2C peripheral, so that we have both
-# on-board and off-board I2C available.
-# When SPIM3 becomes available we'll be able to have two I2C and two SPI peripherals.
-# We use a CFLAGS define here because there are include order issues
-# if we try to include "mpconfigport.h" into nrfx_config.h .
-CFLAGS += -DCIRCUITPY_NRF_NUM_I2C=2
diff --git a/ports/nrf/boards/circuitplayground_bluefruit/mpconfigboard.mk b/ports/nrf/boards/circuitplayground_bluefruit/mpconfigboard.mk
index 38c993334..6b5c0424f 100644
--- a/ports/nrf/boards/circuitplayground_bluefruit/mpconfigboard.mk
+++ b/ports/nrf/boards/circuitplayground_bluefruit/mpconfigboard.mk
@@ -8,9 +8,3 @@ MCU_CHIP = nrf52840
 QSPI_FLASH_FILESYSTEM = 1
 EXTERNAL_FLASH_DEVICE_COUNT = 1
 EXTERNAL_FLASH_DEVICES = "GD25Q16C"
-
-# Allocate two, not just one I2C peripheral for CPB, so that we have both
-# on-board and off-board I2C available.
-# We use a CFLAGS define here because there are include order issues
-# if we try to include "mpconfigport.h" into nrfx_config.h .
-CFLAGS += -DCIRCUITPY_NRF_NUM_I2C=2
diff --git a/ports/nrf/boards/common.template.ld b/ports/nrf/boards/common.template.ld
index 5982b8ba0..192215eee 100644
--- a/ports/nrf/boards/common.template.ld
+++ b/ports/nrf/boards/common.template.ld
@@ -18,13 +18,16 @@ MEMORY
     FLASH_BOOTLOADER_SETTINGS (r) : ORIGIN = ${BOOTLOADER_SETTINGS_START_ADDR}, LENGTH = ${BOOTLOADER_SETTINGS_SIZE}
 
 
-    /* 0x2000000 - RAM:ORIGIN is reserved for Softdevice */
-    /* SoftDevice 6.1.0 with 5 connections and various increases takes just under 64kiB.
-    /* To measure the minimum required amount of memory for given configuration, set this number
-       high enough to work and then check the mutation of the value done by sd_ble_enable. */
-    SPIM3_RAM (rw)  : ORIGIN = 0x20000000 + ${SOFTDEVICE_RAM_SIZE}, LENGTH = ${SPIM3_BUFFER_SIZE}
-    RAM (xrw)       : ORIGIN = 0x20000000 + ${SOFTDEVICE_RAM_SIZE} + ${SPIM3_BUFFER_SIZE}, LENGTH = ${RAM_SIZE} - ${SOFTDEVICE_RAM_SIZE} -${SPIM3_BUFFER_SIZE}
-
+    /* SoftDevice RAM must start at the beginning of RAM: 0x2000000 (RAM_START_ADDR).
+       On nRF52840, the first 64kB of RAM is composed of 8 8kB RAM blocks. Above those is
+       RAM block 8, which is 192kB.
+       If SPIM3_BUFFER_RAM_SIZE is 8kB, as opposed to zero, it must be in the first 64kB of RAM.
+       So the amount of RAM reserved for the SoftDevice must be no more than 56kB.
+    */
+    RAM (xrw)       : ORIGIN = ${RAM_START_ADDR}, LENGTH = ${RAM_SIZE}
+    SD_RAM (rw)     : ORIGIN = ${SOFTDEVICE_RAM_START_ADDR}, LENGTH = ${SOFTDEVICE_RAM_SIZE}
+    SPIM3_RAM (rw)  : ORIGIN = ${SPIM3_BUFFER_RAM_START_ADDR}, LENGTH = ${SPIM3_BUFFER_RAM_SIZE}
+    APP_RAM (xrw)   : ORIGIN = ${APP_RAM_START_ADDR}, LENGTH = ${APP_RAM_SIZE}
 }
 
 /* produce a link error if there is not this amount of RAM available */
@@ -32,16 +35,16 @@ _minimum_heap_size = 0;
 
 /* top end of the stack */
 
-/*_stack_end = ORIGIN(RAM) + LENGTH(RAM);*/
-_estack = ORIGIN(RAM) + LENGTH(RAM);
+/*_stack_end = ORIGIN(APP_RAM) + LENGTH(APP_RAM);*/
+_estack = ORIGIN(APP_RAM) + LENGTH(APP_RAM);
 
 /* RAM extents for the garbage collector */
-_ram_end = ORIGIN(RAM) + LENGTH(RAM);
+_ram_end = ORIGIN(APP_RAM) + LENGTH(APP_RAM);
 _heap_end = 0x20020000; /* tunable */
 
 /* nrf52840 SPIM3 needs its own area to work around hardware problems. Nothing else may use this space. */
 _spim3_ram = ORIGIN(SPIM3_RAM);
-_spim3_ram_end = ORIGIN(SPIM3_RAM) + LENGTH(RAM);
+_spim3_ram_end = ORIGIN(SPIM3_RAM) + LENGTH(SPIM3_RAM);
 
 /* define output sections */
 SECTIONS
@@ -87,7 +90,7 @@ SECTIONS
 
         . = ALIGN(4);
         _edata = .;        /* define a global symbol at data end; used by startup code in order to initialise the .data section in RAM */
-    } >RAM
+    } >APP_RAM
 
     /* Zero-initialized data section */
     .bss :
@@ -100,7 +103,7 @@ SECTIONS
 
         . = ALIGN(4);
         _ebss = .;         /* define a global symbol at bss end; used by startup code and GC */
-    } >RAM
+    } >APP_RAM
 
     /* Uninitialized data section
     Data placed into this section will remain unchanged across reboots. */
@@ -113,7 +116,7 @@ SECTIONS
 
         . = ALIGN(4);
         _euninitialized = .; /* define a global symbol at uninitialized end; currently unused */
-    } >RAM
+    } >APP_RAM
 
     /* this is to define the start of the heap, and make sure we have a minimum size */
     .heap :
@@ -123,7 +126,7 @@ SECTIONS
 	      PROVIDE ( _end = . );
         _heap_start = .;    /* define a global symbol at heap start */
         . = . + _minimum_heap_size;
-    } >RAM
+    } >APP_RAM
 
     /* this just checks there is enough RAM for the stack */
     .stack :
@@ -131,7 +134,7 @@ SECTIONS
         . = ALIGN(4);
         . = . + ${CIRCUITPY_DEFAULT_STACK_SIZE};
         . = ALIGN(4);
-    } >RAM
+    } >APP_RAM
 
     /* Remove exception unwinding information, since Circuit Python
        does not support this GCC feature. */
diff --git a/ports/nrf/boards/hiibot_bluefi/mpconfigboard.mk b/ports/nrf/boards/hiibot_bluefi/mpconfigboard.mk
index e43639a89..d60124348 100644
--- a/ports/nrf/boards/hiibot_bluefi/mpconfigboard.mk
+++ b/ports/nrf/boards/hiibot_bluefi/mpconfigboard.mk
@@ -8,10 +8,3 @@ MCU_CHIP = nrf52840
 QSPI_FLASH_FILESYSTEM = 1
 EXTERNAL_FLASH_DEVICE_COUNT = 1
 EXTERNAL_FLASH_DEVICES = "W25Q16JV_IQ"
-
-# Allocate two, not just one I2C peripheral for Bluefi, so that we have both
-# on-board and off-board I2C available.
-# When SPIM3 becomes available we'll be able to have two I2C and two SPI peripherals.
-# We use a CFLAGS define here because there are include order issues
-# if we try to include "mpconfigport.h" into nrfx_config.h .
-CFLAGS += -DCIRCUITPY_NRF_NUM_I2C=2
diff --git a/ports/nrf/boards/pca10100/mpconfigboard.h b/ports/nrf/boards/pca10100/mpconfigboard.h
index c645b778b..4639a208b 100644
--- a/ports/nrf/boards/pca10100/mpconfigboard.h
+++ b/ports/nrf/boards/pca10100/mpconfigboard.h
@@ -46,3 +46,5 @@
 #define BLEIO_PERIPH_ROLE_COUNT 2
 #define BLEIO_TOTAL_CONNECTION_COUNT 2
 #define BLEIO_ATTR_TAB_SIZE (BLE_GATTS_ATTR_TAB_SIZE_DEFAULT * 2)
+
+#define SOFTDEVICE_RAM_SIZE (32*1024)
diff --git a/ports/nrf/boards/pca10100/mpconfigboard.mk b/ports/nrf/boards/pca10100/mpconfigboard.mk
index e15bf3a67..a8cacbafc 100644
--- a/ports/nrf/boards/pca10100/mpconfigboard.mk
+++ b/ports/nrf/boards/pca10100/mpconfigboard.mk
@@ -27,9 +27,5 @@ CIRCUITPY_ULAB = 0
 
 SUPEROPT_GC = 0
 
-# These defines must be overridden before mpconfigboard.h is included, which is
-# why they are passed on the command line.
-CFLAGS += -DSPIM3_BUFFER_SIZE=0 -DSOFTDEVICE_RAM_SIZE='(32*1024)'
-
 # Override optimization to keep binary small
 OPTIMIZATION_FLAGS = -Os
diff --git a/ports/nrf/boards/simmel/mpconfigboard.h b/ports/nrf/boards/simmel/mpconfigboard.h
index 28c4ee7d9..2380a8055 100644
--- a/ports/nrf/boards/simmel/mpconfigboard.h
+++ b/ports/nrf/boards/simmel/mpconfigboard.h
@@ -52,3 +52,5 @@
 #define BLEIO_PERIPH_ROLE_COUNT 2
 #define BLEIO_TOTAL_CONNECTION_COUNT 2
 #define BLEIO_ATTR_TAB_SIZE (BLE_GATTS_ATTR_TAB_SIZE_DEFAULT * 2)
+
+#define SOFTDEVICE_RAM_SIZE (32*1024)
diff --git a/ports/nrf/boards/simmel/mpconfigboard.mk b/ports/nrf/boards/simmel/mpconfigboard.mk
index 8dd284d57..e34739c0f 100644
--- a/ports/nrf/boards/simmel/mpconfigboard.mk
+++ b/ports/nrf/boards/simmel/mpconfigboard.mk
@@ -29,9 +29,5 @@ CIRCUITPY_WATCHDOG = 1
 # Enable micropython.native
 #CIRCUITPY_ENABLE_MPY_NATIVE = 1
 
-# These defines must be overridden before mpconfigboard.h is included, which is
-# why they are passed on the command line.
-CFLAGS += -DSPIM3_BUFFER_SIZE=0 -DSOFTDEVICE_RAM_SIZE='(32*1024)' -DNRFX_SPIM3_ENABLED=0
-
 # Override optimization to keep binary small
 OPTIMIZATION_FLAGS = -Os
diff --git a/ports/nrf/common-hal/_bleio/Adapter.c b/ports/nrf/common-hal/_bleio/Adapter.c
index 0b23bb7bf..22cd0684f 100644
--- a/ports/nrf/common-hal/_bleio/Adapter.c
+++ b/ports/nrf/common-hal/_bleio/Adapter.c
@@ -61,7 +61,7 @@
 #endif
 
 #ifndef BLEIO_HVN_TX_QUEUE_SIZE
-#define BLEIO_HVN_TX_QUEUE_SIZE 9
+#define BLEIO_HVN_TX_QUEUE_SIZE 5
 #endif
 
 #ifndef BLEIO_CENTRAL_ROLE_COUNT
@@ -120,11 +120,11 @@ STATIC uint32_t ble_stack_enable(void) {
     // Start with no event handlers, etc.
     ble_drv_reset();
 
-    // Set everything up to have one persistent code editing connection and one user managed
-    // connection. In the future we could move .data and .bss to the other side of the stack and
+    // In the future we might move .data and .bss to the other side of the stack and
     // dynamically adjust for different memory requirements of the SD based on boot.py
-    // configuration.
-    uint32_t app_ram_start = (uint32_t) &_ram_start;
+    // configuration. But we still need to keep the SPIM3 buffer (if needed) in the first 64kB of RAM.
+
+    uint32_t sd_ram_end = SOFTDEVICE_RAM_START_ADDR + SOFTDEVICE_RAM_SIZE;
 
     ble_cfg_t ble_conf;
     ble_conf.conn_cfg.conn_cfg_tag = BLE_CONN_CFG_TAG_CUSTOM;
@@ -135,7 +135,7 @@ STATIC uint32_t ble_stack_enable(void) {
     // Event length here can influence throughput so perhaps make multiple connection profiles
     // available.
     ble_conf.conn_cfg.params.gap_conn_cfg.event_length = BLE_GAP_EVENT_LENGTH_DEFAULT;
-    err_code = sd_ble_cfg_set(BLE_CONN_CFG_GAP, &ble_conf, app_ram_start);
+    err_code = sd_ble_cfg_set(BLE_CONN_CFG_GAP, &ble_conf, sd_ram_end);
     if (err_code != NRF_SUCCESS) {
         return err_code;
     }
@@ -147,7 +147,7 @@ STATIC uint32_t ble_stack_enable(void) {
     ble_conf.gap_cfg.role_count_cfg.periph_role_count = BLEIO_PERIPH_ROLE_COUNT;
     // central_role_count costs 648 bytes for 1 to 2, then ~1250 for each further increment.
     ble_conf.gap_cfg.role_count_cfg.central_role_count = BLEIO_CENTRAL_ROLE_COUNT;
-    err_code = sd_ble_cfg_set(BLE_GAP_CFG_ROLE_COUNT, &ble_conf, app_ram_start);
+    err_code = sd_ble_cfg_set(BLE_GAP_CFG_ROLE_COUNT, &ble_conf, sd_ram_end);
     if (err_code != NRF_SUCCESS) {
         return err_code;
     }
@@ -158,7 +158,7 @@ STATIC uint32_t ble_stack_enable(void) {
     // DevZone recommends not setting this directly, but instead changing gap_conn_cfg.event_length.
     // However, we are setting connection extension, so this seems to make sense.
     ble_conf.conn_cfg.params.gatts_conn_cfg.hvn_tx_queue_size = BLEIO_HVN_TX_QUEUE_SIZE;
-    err_code = sd_ble_cfg_set(BLE_CONN_CFG_GATTS, &ble_conf, app_ram_start);
+    err_code = sd_ble_cfg_set(BLE_CONN_CFG_GATTS, &ble_conf, sd_ram_end);
     if (err_code != NRF_SUCCESS) {
         return err_code;
     }
@@ -167,7 +167,7 @@ STATIC uint32_t ble_stack_enable(void) {
     memset(&ble_conf, 0, sizeof(ble_conf));
     ble_conf.conn_cfg.conn_cfg_tag = BLE_CONN_CFG_TAG_CUSTOM;
     ble_conf.conn_cfg.params.gatt_conn_cfg.att_mtu = BLE_GATTS_VAR_ATTR_LEN_MAX;
-    err_code = sd_ble_cfg_set(BLE_CONN_CFG_GATT, &ble_conf, app_ram_start);
+    err_code = sd_ble_cfg_set(BLE_CONN_CFG_GATT, &ble_conf, sd_ram_end);
     if (err_code != NRF_SUCCESS) {
         return err_code;
     }
@@ -177,7 +177,7 @@ STATIC uint32_t ble_stack_enable(void) {
     memset(&ble_conf, 0, sizeof(ble_conf));
     // Each increment to the BLE_GATTS_ATTR_TAB_SIZE_DEFAULT multiplier costs 1408 bytes.
     ble_conf.gatts_cfg.attr_tab_size.attr_tab_size = BLEIO_ATTR_TAB_SIZE;
-    err_code = sd_ble_cfg_set(BLE_GATTS_CFG_ATTR_TAB_SIZE, &ble_conf, app_ram_start);
+    err_code = sd_ble_cfg_set(BLE_GATTS_CFG_ATTR_TAB_SIZE, &ble_conf, sd_ram_end);
     if (err_code != NRF_SUCCESS) {
         return err_code;
     }
@@ -187,13 +187,15 @@ STATIC uint32_t ble_stack_enable(void) {
     memset(&ble_conf, 0, sizeof(ble_conf));
     // Each additional vs_uuid_count costs 16 bytes.
     ble_conf.common_cfg.vs_uuid_cfg.vs_uuid_count = BLEIO_VS_UUID_COUNT; // Defaults to 10.
-    err_code = sd_ble_cfg_set(BLE_COMMON_CFG_VS_UUID, &ble_conf, app_ram_start);
+    err_code = sd_ble_cfg_set(BLE_COMMON_CFG_VS_UUID, &ble_conf, sd_ram_end);
     if (err_code != NRF_SUCCESS) {
         return err_code;
     }
 
-    // This sets app_ram_start to the minimum value needed for the settings set above.
-    err_code = sd_ble_enable(&app_ram_start);
+    // This sets sd_ram_end to the minimum value needed for the settings set above.
+    // You can set a breakpoint just after this call and examine sd_ram_end to see
+    // how much RAM the SD needs with the configuration above.
+    err_code = sd_ble_enable(&sd_ram_end);
     if (err_code != NRF_SUCCESS) {
         return err_code;
     }
diff --git a/ports/nrf/common-hal/busio/SPI.c b/ports/nrf/common-hal/busio/SPI.c
index f27f0e267..521347d83 100644
--- a/ports/nrf/common-hal/busio/SPI.c
+++ b/ports/nrf/common-hal/busio/SPI.c
@@ -41,7 +41,7 @@ STATIC spim_peripheral_t spim_peripherals[] = {
     // Allocate SPIM3 first.
     { .spim = NRFX_SPIM_INSTANCE(3),
       .max_frequency = 32000000,
-      .max_xfer_size = MIN(SPIM3_BUFFER_SIZE, (1UL << SPIM3_EASYDMA_MAXCNT_SIZE) - 1)
+      .max_xfer_size = MIN(SPIM3_BUFFER_RAM_SIZE, (1UL << SPIM3_EASYDMA_MAXCNT_SIZE) - 1)
     },
 #endif
 #if NRFX_CHECK(NRFX_SPIM2_ENABLED)
@@ -71,8 +71,7 @@ STATIC bool never_reset[MP_ARRAY_SIZE(spim_peripherals)];
 
 // Separate RAM area for SPIM3 transmit buffer to avoid SPIM3 hardware errata.
 // https://infocenter.nordicsemi.com/index.jsp?topic=%2Ferrata_nRF52840_Rev2%2FERR%2FnRF52840%2FRev2%2Flatest%2Fanomaly_840_198.html
-extern uint32_t _spim3_ram;
-STATIC uint8_t *spim3_transmit_buffer = (uint8_t *) &_spim3_ram;
+STATIC uint8_t *spim3_transmit_buffer = (uint8_t *) SPIM3_BUFFER_RAM_START_ADDR;
 
 void spi_reset(void) {
     for (size_t i = 0 ; i < MP_ARRAY_SIZE(spim_peripherals); i++) {
diff --git a/ports/nrf/ld_defines.c b/ports/nrf/ld_defines.c
index 8430daccb..6e266e4f7 100644
--- a/ports/nrf/ld_defines.c
+++ b/ports/nrf/ld_defines.c
@@ -10,6 +10,7 @@
 // START_LD_DEFINES
 
 /*FLASH_SIZE=*/                                     FLASH_SIZE;
+/*RAM_START_ADDR=*/                                 RAM_START_ADDR;
 /*RAM_SIZE=*/                                       RAM_SIZE;
 
 /*MBR_START_ADDR=*/                                 MBR_START_ADDR;
@@ -41,5 +42,11 @@
 /*BOOTLOADER_SETTINGS_START_ADDR=*/                 BOOTLOADER_SETTINGS_START_ADDR;
 /*BOOTLOADER_SETTINGS_SIZE=*/                       BOOTLOADER_SETTINGS_SIZE;
 
+/*SOFTDEVICE_RAM_START_ADDR=*/                      SOFTDEVICE_RAM_START_ADDR;
 /*SOFTDEVICE_RAM_SIZE=*/                            SOFTDEVICE_RAM_SIZE;
-/*SPIM3_BUFFER_SIZE=*/                              SPIM3_BUFFER_SIZE;
+
+/*SPIM3_BUFFER_RAM_START_ADDR=*/                    SPIM3_BUFFER_RAM_START_ADDR;
+/*SPIM3_BUFFER_RAM_SIZE=*/                          SPIM3_BUFFER_RAM_SIZE;
+
+/*APP_RAM_START_ADDR=*/                             APP_RAM_START_ADDR;
+/*APP_RAM_SIZE=*/                                   APP_RAM_SIZE;
diff --git a/ports/nrf/mpconfigport.h b/ports/nrf/mpconfigport.h
index 4e49568ed..36a9819dc 100644
--- a/ports/nrf/mpconfigport.h
+++ b/ports/nrf/mpconfigport.h
@@ -34,43 +34,36 @@
 #include "nrf_sdm.h"  // for SD_FLASH_SIZE
 #include "peripherals/nrf/nvm.h" // for FLASH_PAGE_SIZE
 
-// Max RAM used by SoftDevice. Can be changed when SoftDevice parameters are changed.
-// See common.template.ld.
-#ifndef SOFTDEVICE_RAM_SIZE
-#define SOFTDEVICE_RAM_SIZE         (64*1024)
-#endif
+#define MICROPY_PY_COLLECTIONS_ORDEREDDICT       (1)
+#define MICROPY_PY_FUNCTION_ATTRS                (1)
+#define MICROPY_PY_IO                            (1)
+#define MICROPY_PY_REVERSE_SPECIAL_METHODS       (1)
+#define MICROPY_PY_SYS_STDIO_BUFFER              (1)
+#define MICROPY_PY_UBINASCII                     (1)
+#define MICROPY_PY_UJSON                         (1)
+
+// 24kiB stack
+#define CIRCUITPY_DEFAULT_STACK_SIZE            (24*1024)
 
 #ifdef NRF52840
 #define MICROPY_PY_SYS_PLATFORM "nRF52840"
-#define FLASH_SIZE                  (0x100000)  // 1MiB
-#define RAM_SIZE                    (0x40000)   // 256 KiB
+#define FLASH_SIZE                  (1024*1024)  // 1MiB
+#define RAM_SIZE                    (256*1024)   // 256 KiB
 // Special RAM area for SPIM3 transmit buffer, to work around hardware bug.
 // See common.template.ld.
-#define SPIM3_BUFFER_SIZE           (8192)
+#define SPIM3_BUFFER_RAM_SIZE       (8*1024)     // 8 KiB
 #endif
 
 #ifdef NRF52833
 #define MICROPY_PY_SYS_PLATFORM "nRF52833"
-#define FLASH_SIZE                  (0x80000)  // 512 KiB
-#define RAM_SIZE                    (0x20000)  // 128 KiB
-// Special RAM area for SPIM3 transmit buffer, to work around hardware bug.
-// See common.template.ld.
-#ifndef SPIM3_BUFFER_SIZE
-#define SPIM3_BUFFER_SIZE           (8192)
+#define FLASH_SIZE                  (512*1024)  // 512 KiB
+#define RAM_SIZE                    (128*1024)  // 128 KiB
+// SPIM3 buffer is not needed on nRF52833: the SPIM3 hw bug is not present.
+#ifndef SPIM3_BUFFER_RAM_SIZE
+#define SPIM3_BUFFER_RAM_SIZE       (0)
 #endif
 #endif
 
-#define MICROPY_PY_COLLECTIONS_ORDEREDDICT       (1)
-#define MICROPY_PY_FUNCTION_ATTRS                (1)
-#define MICROPY_PY_IO                            (1)
-#define MICROPY_PY_REVERSE_SPECIAL_METHODS       (1)
-#define MICROPY_PY_SYS_STDIO_BUFFER              (1)
-#define MICROPY_PY_UBINASCII                     (1)
-#define MICROPY_PY_UJSON                         (1)
-
-// 24kiB stack
-#define CIRCUITPY_DEFAULT_STACK_SIZE            0x6000
-
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
 // This also includes mpconfigboard.h.
@@ -79,7 +72,7 @@
 // Definitions that might be overriden by mpconfigboard.h
 
 #ifndef CIRCUITPY_INTERNAL_NVM_SIZE
-#define CIRCUITPY_INTERNAL_NVM_SIZE (8192)
+#define CIRCUITPY_INTERNAL_NVM_SIZE (8*1024)
 #endif
 
 #ifndef BOARD_HAS_32KHZ_XTAL
@@ -88,11 +81,11 @@
 #endif
 
 #if INTERNAL_FLASH_FILESYSTEM
-  #ifndef CIRCUITPY_INTERNAL_FLASH_FILESYSTEM_SIZE
-    #define CIRCUITPY_INTERNAL_FLASH_FILESYSTEM_SIZE (256*1024)
-  #endif
+#ifndef CIRCUITPY_INTERNAL_FLASH_FILESYSTEM_SIZE
+#define CIRCUITPY_INTERNAL_FLASH_FILESYSTEM_SIZE (256*1024)
+#endif
 #else
-  #define CIRCUITPY_INTERNAL_FLASH_FILESYSTEM_SIZE (0)
+#define CIRCUITPY_INTERNAL_FLASH_FILESYSTEM_SIZE (0)
 #endif
 
 // Flash layout, starting at 0x00000000
@@ -116,7 +109,7 @@
 
 // SD_FLASH_SIZE is from nrf_sdm.h
 #define ISR_START_ADDR  (SD_FLASH_START_ADDR + SD_FLASH_SIZE)
-#define ISR_SIZE        (0x1000)   // 4kiB
+#define ISR_SIZE        (4*1024)   // 4kiB
 
 // Smallest unit of flash that can be erased.
 #define FLASH_ERASE_SIZE FLASH_PAGE_SIZE
@@ -127,12 +120,12 @@
 
 // Bootloader values from https://github.com/adafruit/Adafruit_nRF52_Bootloader/blob/master/src/linker/s140_v6.ld
 #define BOOTLOADER_START_ADDR          (FLASH_SIZE - BOOTLOADER_SIZE - BOOTLOADER_SETTINGS_SIZE - BOOTLOADER_MBR_SIZE)
-#define BOOTLOADER_MBR_SIZE            (0x1000)     // 4kib
+#define BOOTLOADER_MBR_SIZE            (4*1024)     // 4kib
 #ifndef BOOTLOADER_SIZE
-#define BOOTLOADER_SIZE                (0xA000)     // 40kiB
+#define BOOTLOADER_SIZE                (40*1024)     // 40kiB
 #endif
 #define BOOTLOADER_SETTINGS_START_ADDR (FLASH_SIZE - BOOTLOADER_SETTINGS_SIZE)
-#define BOOTLOADER_SETTINGS_SIZE       (0x1000)     // 4kiB
+#define BOOTLOADER_SETTINGS_SIZE       (4*1024)     // 4kiB
 
 #define CIRCUITPY_INTERNAL_FLASH_FILESYSTEM_START_ADDR (BOOTLOADER_START_ADDR - CIRCUITPY_INTERNAL_FLASH_FILESYSTEM_SIZE)
 
@@ -180,11 +173,46 @@
 #error No space left in flash for firmware after specifying other regions!
 #endif
 
+////////////////////////////////////////////////////////////////////////////////////////////////////
+// RAM space definitions
+
+// Max RAM used by SoftDevice. Can be changed when SoftDevice parameters are changed.
+// On nRF52840, the first 64kB of RAM is composed of 8 8kB RAM blocks. Above those is
+// RAM block 8, which is 192kB.
+// If SPIM3_BUFFER_RAM_SIZE is 8kB, as opposed to zero, it must be in the first 64kB of RAM.
+// So the amount of RAM reserved for the SoftDevice must be no more than 56kB.
+// SoftDevice 6.1.0 with 5 connections and various increases can be made to use < 56kB.
+// To measure the minimum required amount of memory for given configuration, set this number
+// high enough to work and then check the mutation of the value done by sd_ble_enable().
+// See common.template.ld.
+#ifndef SOFTDEVICE_RAM_SIZE
+#define SOFTDEVICE_RAM_SIZE         (56*1024)
+#endif
+
+
+#define RAM_START_ADDR              (0x20000000)
+#define SOFTDEVICE_RAM_START_ADDR   (RAM_START_ADDR)
+#define SPIM3_BUFFER_RAM_START_ADDR (SOFTDEVICE_RAM_START_ADDR + SOFTDEVICE_RAM_SIZE)
+#define APP_RAM_START_ADDR          (SPIM3_BUFFER_RAM_START_ADDR + SPIM3_BUFFER_RAM_SIZE)
+#define APP_RAM_SIZE                (RAM_START_ADDR + RAM_SIZE - APP_RAM_START_ADDR)
+
+#if SPIM3_BUFFER_RAM_SIZE > 0 && SOFTDEVICE_RAM_SIZE + SPIM3_BUFFER_RAM_SIZE > (64*1024)
+#error SPIM3 buffer must be in the first 64kB of RAM.
+#endif
+
+#if SOFTDEVICE_RAM_SIZE + SPIM3_BUFFER_RAM_SIZE + APP_RAM_SIZE > RAM_SIZE
+#error RAM size regions overflow RAM
+#endif
+
+#if SOFTDEVICE_RAM_SIZE + SPIM3_BUFFER_RAM_SIZE + APP_RAM_SIZE < RAM_SIZE
+#error RAM size regions do not use all of RAM
+#endif
+
 
-#define MICROPY_PORT_ROOT_POINTERS \
-    CIRCUITPY_COMMON_ROOT_POINTERS \
-    uint16_t* pixels_pattern_heap; \
-    ble_drv_evt_handler_entry_t* ble_drv_evt_handler_entries; \
+#define MICROPY_PORT_ROOT_POINTERS                              \
+    CIRCUITPY_COMMON_ROOT_POINTERS                              \
+    uint16_t* pixels_pattern_heap;                              \
+    ble_drv_evt_handler_entry_t* ble_drv_evt_handler_entries;   \
 
 
 #endif  // NRF5_MPCONFIGPORT_H__
diff --git a/ports/nrf/nrfx_config.h b/ports/nrf/nrfx_config.h
index b528a6032..94812d591 100644
--- a/ports/nrf/nrfx_config.h
+++ b/ports/nrf/nrfx_config.h
@@ -5,7 +5,7 @@
 #define NRFX_POWER_ENABLED 1
 #define NRFX_POWER_DEFAULT_CONFIG_IRQ_PRIORITY 7
 
-// NOTE: THIS WORKAROUND CAUSES BLE CODE TO CRASH.
+// NOTE: THIS WORKAROUND CAUSES BLE CODE TO CRASH. DO NOT USE.
 // It doesn't work with the SoftDevice.
 // See https://devzone.nordicsemi.com/f/nordic-q-a/33982/sdk-15-software-crash-during-spi-session
 // Turn on nrfx supported workarounds for errata in Rev1 of nRF52840