Questions regarding nRF52832 for specific application

[Rahul Shah]

Hi, I have a specific application/product where in I am planning to use Nordic nRF52832.

-> There is a 9 Axis Inertial Measurement Unit (accel/gyro/magnetometer) connected to I2C port of nRF52832 -> Per second I have to sample approx. 300Kbits of data from the 9 axis sensor over I2C.

-> At the same time the sampled data should be transmitted over BLE to smartphone.

I seek some quick answers to the below mentioned questions.

1. Will I be able to sample 300Kbits of data over I2C running at 400 KHz in 1 second? Else what time will it take?
2. Will BLE stack run simultaneously?
3. If not what will be the latency?
4. How much time will it take for nRF52832 to transmit 300 Kbits data to smartphone?
5. While BLE stack is in operation, can there be any other priority interrupts possible?
6. In case I design an architecture wherein the data is first captured and then transmitted, can 300Kbits data be saved in internal ROM or will it be saved in data RAM?

Thank you in advance Regards Rahul Shah

[Wojtek]

Ad1. I don't think so - 400KHz wouldn't be enough because you probably have to switch between registers, request data, etc. Protocol has some overhead that just takes some cycles. You need to check exactly how your device communicates and just count bytes needed...

Ad4. That mostly depends of the maximum throughput of the smartphone (differs between devices). This may be helpful.

Ad6. Why don't you just do simple maths to calculate this? You can use internal rom if you have enough space - nrf52832 has 512kB ROM AFAIR. Your program probably wouldn't take much space so you can store data in ROM. however, i highly wouldn't recommend that because of limited write-cycles and time needed to store the data. I don't know how much RAM S132 needs, but 64kB may not be enough to store your samples and all the program data.

[Petter Myhre]

Ad2. If you are in a connection the BLE stack needs to be running.

Ad3. If you are not in a connection the peripheral needs to advertise, the phone needs to scan. The connection must be established, and you may have to do service discovery, if you haven't bonded to avoid this. The time it takes to do this depends on the advertising interval, scan interval and scan window, and connection interval, so it is difficult to give you an exact time.

Ad5. The radio and the link layer has the higest priority. Have a look at this for more information. If you want to make sure you are not interrupted for a certain timeslot, you have have a look at the Timeslot API.