nrf51822 evaluation kit image from camera to BLE

RE: nrf51822 evaluation kit image from camera to BLE

Stefan Birnir Sverrisson — Tue, 09 Dec 2014 15:23:39 GMT

There is a pstorage example available at the bottom of this thread.

There is also a getting started guide here for the nRF51.

RE: nrf51822 evaluation kit image from camera to BLE

Dong Pham — Tue, 09 Dec 2014 01:24:25 GMT

Right now! I try to get a demo, which mean just need an complete image after sending through ble. I approach with ble_app_uart and simple_uart main files. I have some ideas:

-uint8_t simple_uart_get(void) // get data from RXD pin

-bool simple_uart_get_with_timeout(int32_t timeout_ms, uint8_t * rx_data) //get data and delay

-void simple_uart_put(uint8_t cr) // put data to TXD pin

-void simple_uart_putstring(const uint8_t * str) //ble_app_uart call this function,not sure what it does

-static void advertising_init(void) // setup first conditions for ble

-void uart_data_handler(ble_nus_t * p_nus, uint8_t * data, uint16_t length) // put data to handler

-static void advertising_start(void) // send to ble

Other functions in those main.c, i dont really understand fully, or do i really need all of them? Let me know if i miss something or misunderstand something Best regard

RE: nrf51822 evaluation kit image from camera to BLE

Salman — Mon, 08 Dec 2014 06:57:11 GMT

You should not store the image in flash. You need a SD card, external RAM or ROM for that. It is a good option to use SD card. Read all data from camera on serial interrupt and write it in SD card. You can write on SD card as RAW bytes. SD card writes and reads 512 bytes at a time so you need to make 2 512 bytes buffers this is because when buffer 1 is full you need to start receiving data on buffer 2 mean while write the data in buffer 1 to SD card. I have tried this and this logic works. One thing more you can reduce the size of image by sending it ratio command that why image size will be small.

RE: nrf51822 evaluation kit image from camera to BLE

Nguyen Hoan Hoang — Sun, 07 Dec 2014 03:08:01 GMT

First things, put your camera aside for a while. Take UART and other ble examples and get them working. Get a feel of how BLE works. Once you familiar with data transmission over BLE, then you can get back to your camera. There are many examples in the sdk you can look at. If you are using Keil free licence, it is limited to 30KB. This is probably not enough for real work. There are Eclipse based development which is completely free. You look at this Blog site on how to setup up Eclipse based nRF51 development. It also contains many examples you can use, including UART over BLE. embeddedsoftdev.blogspot.ca/.../ehal-nrf51.html

RE: nrf51822 evaluation kit image from camera to BLE

Dong Pham — Sat, 06 Dec 2014 17:58:40 GMT

since the minimum size of my image is 4k (160x120) and max is 60k(640x480), i think i just go with the min resolution. As Clem Taylor mentioned, if i dont store the image (i will add Winbond later) and i want to go direct to BLE, what direction should i follow? All the response i receive from the camera right now is though my logic analyzer.

RE: nrf51822 evaluation kit image from camera to BLE

Clem Taylor — Sat, 06 Dec 2014 08:06:44 GMT

Many of the jpeg camera modules can buffer the compressed data (some can even store a small ring of compressed frames). So your best bet is to stream the data directly from the uart to the radio and let the camera module act as your buffer.

The on-chip flash really isn't a good choice for writing something like image data. If you really want to write the images to flash first, then use an external SPI flash (something like the Winbond W25Q80BW is US$0.50/Q1 at digikey).

RE: nrf51822 evaluation kit image from camera to BLE

Nguyen Hoan Hoang — Sat, 06 Dec 2014 05:23:08 GMT

I can't to your question about the camera protocol. You'll need to find the camera specification and understand the transfer protocol it uses to transfer data over uart. JPEG is a compressed image. You won't the picture itself but compressed data bitstream. In order to see the image you need to decode it first. You don't need to do that. Just sent all the data you receive and send it as it over BLE to whatever you use to decode the image. The nRF51 is not fast enough to decode the image in realtime.

RE: nrf51822 evaluation kit image from camera to BLE

Dong Pham — Sat, 06 Dec 2014 04:39:27 GMT

Thanks for fast reply and your patience! The camera takes picture with its smallest resolution: 160x120 which means 10k. I receive the first chunk and the last chunk of the picture which starts with FFD8 and FFD9. It's not right because i want to receive all the chunks, not only the first one and the last one. I receive chunks with logic analyzer. 1 more thing, right at that logic analyzer, i am not sure if the image(in hex digit) is in the board nrf51822 or still in the camera. Sorry, i am a very beginner with ARM and Camera

RE: nrf51822 evaluation kit image from camera to BLE

Nguyen Hoan Hoang — Sat, 06 Dec 2014 03:48:56 GMT

All most all the example make use of pstorage you can lookup. It is also described here developer.nordicsemi.com/.../ writing to flash takes a lot times. I guest the image is around 4KB. Probably too much for RAM. You'll probably get 2-3 frames/sec going through RAM. May be 1/s through Flash, may be less.

RE: nrf51822 evaluation kit image from camera to BLE

Dong Pham — Fri, 05 Dec 2014 23:10:34 GMT

What do you mean by "10-second per frame"? Can you explain more about this ?

RE: nrf51822 evaluation kit image from camera to BLE

Marc Nicholas — Fri, 05 Dec 2014 22:57:11 GMT

Do you really want to spend 10-seconds per frame transferring the image? BLE is really not optimal for file transfers...

RE: nrf51822 evaluation kit image from camera to BLE

Dong Pham — Fri, 05 Dec 2014 22:41:13 GMT

The resolution : 160X120 so it wont take too much memory of the Ram/flash What I mean is how do set up the address after taking picture? how to transfer that picture to BLE ?

RE: nrf51822 evaluation kit image from camera to BLE

Nguyen Hoan Hoang — Fri, 05 Dec 2014 21:22:12 GMT

You need to look at the pstorage. How big is the picture ? You only have a few KB in the nRF51 flash avail for storage.