increase max connections from 2 to 5

Author: dhalbert

ports/nrf/bluetooth/ble_drv.h

@@ -33,8 +33,6 @@
 
 #include "ble.h"
 
-#define MAX_TX_IN_PROGRESS 10
-
 #ifndef BLE_GATT_ATT_MTU_DEFAULT
     #define BLE_GATT_ATT_MTU_DEFAULT GATT_MTU_SIZE_DEFAULT
 #endif

ports/nrf/boards/common.template.ld

@@ -19,14 +19,13 @@ MEMORY
 
 
     /* 0x2000000 - RAM:ORIGIN is reserved for Softdevice */
-    /* SoftDevice 6.1.0 takes 0x7b78 bytes (30.86 kb) minimum with high ATT MTU. */
+    /* 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. */
-    RAM (xrw)       : ORIGIN = 0x20000000 + 32K, LENGTH = 256K - 32K
+    RAM (xrw)       : ORIGIN = 0x20000000 + 64K, LENGTH = 256K - 64K
 }
 
-/* produce a link error if there is not this amount of RAM for these sections */
-_minimum_stack_size = 40K;
+/* produce a link error if there is not this amount of RAM available */
 _minimum_heap_size = 0;
 
 /* top end of the stack */
@@ -125,7 +124,7 @@ SECTIONS
     .stack :
     {
         . = ALIGN(4);
-        . = . + _minimum_stack_size;
+        . = . + ${CIRCUITPY_DEFAULT_STACK_SIZE};
         . = ALIGN(4);
     } >RAM
 

ports/nrf/common-hal/_bleio/Adapter.c

@@ -108,6 +108,9 @@ STATIC uint32_t ble_stack_enable(void) {
 
     ble_cfg_t ble_conf;
     ble_conf.conn_cfg.conn_cfg_tag = BLE_CONN_CFG_TAG_CUSTOM;
+    // Each additional connection costs:
+    // about 3700-4300 bytes when .hvn_tx_queue_size is 1
+    // about 9000 bytes when .hvn_tx_queue_size is 10
     ble_conf.conn_cfg.params.gap_conn_cfg.conn_count = BLEIO_TOTAL_CONNECTION_COUNT;
     // Event length here can influence throughput so perhaps make multiple connection profiles
     // available.
@@ -118,17 +121,23 @@ STATIC uint32_t ble_stack_enable(void) {
     }
 
     memset(&ble_conf, 0, sizeof(ble_conf));
+    // adv_set_count must be == 1 for S140. Cannot be increased.
     ble_conf.gap_cfg.role_count_cfg.adv_set_count = 1;
-    ble_conf.gap_cfg.role_count_cfg.periph_role_count = 2;
-    ble_conf.gap_cfg.role_count_cfg.central_role_count = 1;
+    // periph_role_count costs 1232 bytes for 2 to 3, then ~1840 for each further increment.
+    ble_conf.gap_cfg.role_count_cfg.periph_role_count = 4;
+    // 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 = 4;
     err_code = sd_ble_cfg_set(BLE_GAP_CFG_ROLE_COUNT, &ble_conf, app_ram_start);
     if (err_code != NRF_SUCCESS) {
         return err_code;
     }
 
     memset(&ble_conf, 0, sizeof(ble_conf));
     ble_conf.conn_cfg.conn_cfg_tag = BLE_CONN_CFG_TAG_CUSTOM;
-    ble_conf.conn_cfg.params.gatts_conn_cfg.hvn_tx_queue_size = MAX_TX_IN_PROGRESS;
+    // Each increment to hvn_tx_queue_size costs 2064 bytes.
+    // 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 = 9;
     err_code = sd_ble_cfg_set(BLE_CONN_CFG_GATTS, &ble_conf, app_ram_start);
     if (err_code != NRF_SUCCESS) {
         return err_code;
@@ -143,10 +152,11 @@ STATIC uint32_t ble_stack_enable(void) {
         return err_code;
     }
 
-    // Triple the GATT Server attribute size to accomodate both the CircuitPython built-in service
+    // Increase the GATT Server attribute size to accomodate both the CircuitPython built-in service
     // and anything the user does.
     memset(&ble_conf, 0, sizeof(ble_conf));
-    ble_conf.gatts_cfg.attr_tab_size.attr_tab_size = BLE_GATTS_ATTR_TAB_SIZE_DEFAULT * 3;
+    // Each increment to the BLE_GATTS_ATTR_TAB_SIZE_DEFAULT multiplier costs 1408 bytes.
+    ble_conf.gatts_cfg.attr_tab_size.attr_tab_size = BLE_GATTS_ATTR_TAB_SIZE_DEFAULT * 5;
     err_code = sd_ble_cfg_set(BLE_GATTS_CFG_ATTR_TAB_SIZE, &ble_conf, app_ram_start);
     if (err_code != NRF_SUCCESS) {
         return err_code;
@@ -155,7 +165,8 @@ STATIC uint32_t ble_stack_enable(void) {
     // Increase the number of vendor UUIDs supported. Apple uses a complete random number per
     // service and characteristic.
     memset(&ble_conf, 0, sizeof(ble_conf));
-    ble_conf.common_cfg.vs_uuid_cfg.vs_uuid_count = 32; // Defaults to 10.
+    // Each additional vs_uuid_count costs 16 bytes.
+    ble_conf.common_cfg.vs_uuid_cfg.vs_uuid_count = 75; // Defaults to 10.
     err_code = sd_ble_cfg_set(BLE_COMMON_CFG_VS_UUID, &ble_conf, app_ram_start);
     if (err_code != NRF_SUCCESS) {
         return err_code;

ports/nrf/common-hal/_bleio/Adapter.h

@@ -35,7 +35,7 @@
 #include "shared-bindings/_bleio/Connection.h"
 #include "shared-bindings/_bleio/ScanResults.h"
 
-#define BLEIO_TOTAL_CONNECTION_COUNT 2
+#define BLEIO_TOTAL_CONNECTION_COUNT 5
 
 extern bleio_connection_internal_t bleio_connections[BLEIO_TOTAL_CONNECTION_COUNT];