Using SPI to interface an omnivision camera?

RE: Using SPI to interface an omnivision camera?

Marc Nicholas — Tue, 18 Nov 2014 20:36:46 GMT

Even QCIF would be well beyond the capabilities of the nRF51 (~25K @ 8-bits)....plus it'd take several seconds per frame to transfer via BLE and even using an external SRAM, you also blow-up the short duty-cycle == long battery life use-case too as you'd be running the SPI peripheral continuously.

BLE is just not optimized for these use-cases.

-m

RE: Using SPI to interface an omnivision camera?

Adam — Tue, 18 Nov 2014 20:31:08 GMT

Hi Elena,

Can you specify what model of omnivision camera are you going to use? Generally I agree with Marc that there is not enough memory on the nRF51 to buffer images. Alternatively, you can change the resolution of the camera, e.g. to QCIF resolution (176x144) if this option is available in your camera. For more omnivision cameras settings please visit www.mobilerobots.pl/index.php You should use the TWI code example from Nordic as a base and modify it to your needs. There is a little difference between SCCB and TWI(I2C). In TWI there is an ACK bit after each byte of transmission and in SCCB the slave don't need to send ACK (Don't care bit) - please see the answer in this post devzone.nordicsemi.com/.../

RE: Using SPI to interface an omnivision camera?

Marc Nicholas — Fri, 08 Nov 2013 13:04:25 GMT

Hi Elana,

The cameras use SCCB as a control channel for setup only. It is I2C, but obviously I2C is a Philips trademark/standard....which is why Nordic called their implementation TWI.

To get data out of the camera, you latch a parallel data bus. Often this requires an external buffer IC.

Three problems you'll face:

(1) The amount of bandwidth the camera requires to latch out an image. (2) Lack of enough memory on the nRF51 to buffer that image, requiring an external SRAM instead. (3) The S110 SoftDevice is actually one of the better performing BLE stacks, but you'll be lucky to get 5Kbytes/sec throughput.

-m

RE: Using SPI to interface an omnivision camera?

Pål Håland — Fri, 08 Nov 2013 09:47:08 GMT

Hi Elena,

There is a spi_master_example in the SDK (in Board/nrf6310 folder) devzone.nordicsemi.com/.../group__spi__master__example.html

a driver (spi_master) is there as well (in the Source folder) devzone.nordicsemi.com/.../group__lib__driver__spi__master.html