Another instance - feasible?

[olsky]

Hi, in some earlier versions I do recall there was a possibility to start more instances, is it still the case? Was this tried/tested? I thought to start two/three independent instances on different channels.

Can you please share some infos?

[trond-snekvik]

Could you elaborte a bit? At which level of instancing?

[olsky]

sure, wanted to try 3 independed mesh instances on different radio channels (with own name-value map and own tickle instance).

[trond-snekvik]

Hi, sorry for the delay. I'm afraid you can't start multiple concurrent instances of the mesh on a single chip. I think what you're referring to was meant to be multiple network-instances in a single location, but I don't think the documentation was clear enough. This is of course still possible by setting different channels/access addresses on different devices, but a single device will be restricted to a single configuration at a time in the base mesh-implementation.

If you're still interested in doing multiple instances, there's a way to do this with access addresses in the hardware, but it will require quite extensive additions throughout the stack. I can walk through them for you if you're up for it, but I doubt it will be part of the main version of the mesh-framework, sorry.

[olsky]

Thanks Trond! Yes, I'm interested! :) sounds really cool...

[trond-snekvik]

To do this, we need to change the radio configuration, and expose this change further up the stack.

First, multiple access addresses:

The nRF51 radio has a limited number of access addresses it can match packets to. These addresses are set in the NRF_RADIO->PREFIXn and NRF_RADIO->BASEn registers. In our stack, these are configured in radio_init():

    /* Configure Access Address  */
    NRF_RADIO->PREFIX0      = ((access_address >> 24) & 0x000000FF);
    NRF_RADIO->BASE0        = ((access_address << 8) & 0xFFFFFF00);
    NRF_RADIO->TXADDRESS    = 0x00;             // Use logical address 0 (prefix0 + base0) = 0x8E89BED6 when transmitting
    NRF_RADIO->RXADDRESSES  = 0x01;             // Enable reception on logical address 0 (PREFIX0 + BASE0)

As you can see, we define PREFIX and BASE 0. You can only have two different base addresses, and 8 different prefixes, but you can't mix and match as you want: Table 99 in the nRF51 Reference manual v3.0 (pdf!) defines 8 possible combinations. These indexes defined for each combination is to be used in the NRF_RADIO->TXADDRESS and NRF_RADIO->RXADDRESSES registers. The TXADDRESS is an index (matching the table), the RXADDRESSES is a bitfield, where you can mark which access addresses you want to receive on. After receiving a packet, you can get the index of the address-combination you received on in the NRF_RADIO->RXMATCH register.

Multiple channels:

Channels are a bit easier to deal with than access addresses. Setting the hardware-channel only requires that you set NRF_RADIO->FREQUENCY to the frequency of the BLE channel you want, and setting NRF_RADIO->DATAWHITEIV to the channel index you want. Luckily, this mapping is already done in radio_channel_set(uint8_t ch), so you only need to store the BLE channel, and set it correctly in setup_event(radio_event_t* p_evt).

Passing the parameters:

Configuring a second access address or channel should be as easy as duplicating the access address or channel parameter all the way from the API (or hardcode it, if you won't bother:) ). Binding the access address or channel to the packets you're sending requires more work. I don't know your use-case, but you could either split your handle range into multiple configurations by some global rule, or find a smart way to specify (and store!) them throughout the stack. Sending on the correct TXADDRESS and channel should be solvable by adding extra parameters to the radio_event_t struct.

[olsky]

OMG! :-) you simply rock, Trond!

That's what I was thinking of, but I was not sure if it was feasible (espacially with logical addresses -- I might have overlooked some docs, I will check the RefManual again, just in case -- could you please point to some other nRF docs?)

Thank you alot!

PS: now it gets tricky :-) I simply need some time... that's all :)))

[trond-snekvik]

The three docs that are always open on my computer are

• nRF51 Reference manual: Register overview, HW functionality, module overview
• Softdevice Specification S110: Softdevice S110 resource requirements, timing, API details.
• nRF51822 Product specification: Power consumption, HW module instances, HW timing.

All info relevant for radio config is in the RM (Section 17) :)

[olsky]

Trond: thank you!

I must admit ref-man and prod-spec are my pref read. I must force myself into S110 spec reading...