RedBearLab BLE nano<\/a> (v1.5). It has been tough getting Xcode setup to compile code right, and \u00a0I ended up using \u201cembedXcode\u201d as a starting point, and the Arduino plugin for RedBearLab. I\u2019d rather just use mbed, but the web experience is terrible, and I must use Xcode. However, I couldn\u2019t get their scripts to compile..mainly do to case sensitivity issues (BLE.h and ble.h both exist, and my drive partition is insensitive).\u00a0<\/p>\nFor the Nano, the bottom line was I had to edit the projectconfig.h file and use these settings:<\/p>\n
\u00a0 \u00a0\u00a0#define CFG_GAP_CONNECTION_MIN_INTERVAL_MS \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 <\/span>20<\/span>\/\/ corbin!! fYI, 40 worked. 50 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/**< Minimum acceptable connection interval *\/<\/p>\n\u00a0 \u00a0 #define CFG_GAP_CONNECTION_MAX_INTERVAL_MS\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 <\/span>40<\/span>\/\/ corbin!! 500 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/**< Maximum acceptable connection interval *\/<\/p>\n\u00a0 \u00a0 #define CFG_GAP_CONNECTION_SUPERVISION_TIMEOUT_MS\u00a0 <\/span>500<\/span>\/\/ corbin!! 4000 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/**< Connection supervisory timeout *\/<\/p>\nThe key part was not just the min interval, but the max; 500 was too large, and there is no API to control it (I can add some in for myself). 40 is required. I didn\u2019t test lower\u2026but lower might be better too. Too low, and the Mac (or iOS device) might not be able to keep up.<\/p>\n
\u00a0When sending from an OS X app, I discovered I could get the most data by doing a \u201cwrite without response\u201d:<\/p>\n
\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0peripheral<\/span>.writeValue<\/span>(subData, forCharacteristic: _uartTransmitCharacteristic<\/span>!, type: CBCharacteristicWriteType<\/span>.WithoutResponse<\/span>)<\/p>\n\u00a0And batching the 20 byte data chunks every 2 nano seconds:<\/p>\n
\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0<\/span>let<\/span> delay: <\/span>Int64<\/span> = <\/span>Int64<\/span>(<\/span>NSEC_PER_MSEC<\/span>)*<\/span>2<\/span>\/\/ At about 4ns, it starts to get slower on the recieving end.<\/p>\n\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 <\/span>dispatch_after(<\/span>dispatch_time(<\/span>DISPATCH_TIME_NOW<\/span>, delay), <\/span>dispatch_get_main_queue(), { () -> <\/span>Void<\/span>in<\/span><\/p>\n\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 self<\/span>.sendMoreData<\/span>();<\/p>\n\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 })<\/p>\n
\u00a0Anything longer and it would be slower. This doesn\u2019t make sense\u2026as the BLE stack can\u2019t really be faster than 7.5ms, but I\u2019m sure the computer is doing a bit of processing and handling the BLE stack separately from my process. I have yet to test the code on iOS\u2026it might need a larger delay, and might be slower. That is fine\u2026 my goal is to send files from the desktop to the device, and potentially vice-versa.\u00a0<\/p>\n
With my above changes, a raw read of 1024 bytes (1kB) took 185ms; and it was fairly consistent. That\u2019s about 5.4kB<\/strong> per second! I could probably improve it 6x more by using multiple characteristics to write at simultaneously, but I\u2019ll test that later. 5.4kB\/second is fast enough to start with.<\/p>\n\u00a0<\/p>\n
\u00a0<\/p>\n
I was curious if the Adafruit Bluefruit LE friend<\/strong> could be made faster. I know the GAP interval can be changed, so I made it match with:<\/p>\n\u00a0 \u00a0 \u00a0 \u00a0\u00a0<\/span>m_ble<\/span>.<\/span>sendCommandCheckOK<\/span>(<\/span>“AT+GAPINTERVALS=20,40,25,30”);<\/span><\/p>\n\u00a0<\/div>\n
Indeed, this did help! the UART service can read 1024 bytes in 3.5 seconds, instead of 10 seconds, or about
0.3kB<\/strong>\/second versus 0.1kB\/second. \u00a0This is reading the data from a teensy, which means the Adafruit BLE friend first reads the data, and then transfers it to the teensy over SPI. That protocol is somewhat slow, and it has a 16 byte payload (it really needs to be 20 bytes to transfer complete packets from the BLE).\u00a0<\/div>\n\u00a0<\/div>\n
Of course\u2026my test is ignoring the SPI transfer from the nRF chip to the teensy chip. This is also going to take some time, and might slow my numbers down a bit. I also need to learn how to write SPI code and make my own mechanism for transferring data. Lots more coding to do…<\/div>\n","protected":false},"excerpt":{"rendered":"
I\u2019ve been using the Adafruit LE friend to do some data transfer tests. With the basic setup, I was sending 1 kB of data in about 9.5 to 10 seconds. That is horribly slow! About… [read more]<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[6,86],"tags":[126,127,129,72],"class_list":["post-4281","post","type-post","status-publish","format-standard","hentry","category-cocoa","category-coding","tag-arduino","tag-bluetooth","tag-c","tag-programming"],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.corbinstreehouse.com\/blog\/wp-json\/wp\/v2\/posts\/4281","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.corbinstreehouse.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.corbinstreehouse.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.corbinstreehouse.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.corbinstreehouse.com\/blog\/wp-json\/wp\/v2\/comments?post=4281"}],"version-history":[{"count":2,"href":"https:\/\/www.corbinstreehouse.com\/blog\/wp-json\/wp\/v2\/posts\/4281\/revisions"}],"predecessor-version":[{"id":5321,"href":"https:\/\/www.corbinstreehouse.com\/blog\/wp-json\/wp\/v2\/posts\/4281\/revisions\/5321"}],"wp:attachment":[{"href":"https:\/\/www.corbinstreehouse.com\/blog\/wp-json\/wp\/v2\/media?parent=4281"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.corbinstreehouse.com\/blog\/wp-json\/wp\/v2\/categories?post=4281"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.corbinstreehouse.com\/blog\/wp-json\/wp\/v2\/tags?post=4281"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}