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docs: add Broadcom section

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doc/manual/docs/chipsets.md
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@ -1,11 +1,14 @@
In this chapter, we first explain how Bluetooth chipsets are connected physically and
then provide information about popular Bluetooth chipset and their use with BTstack.
The communication between a Host (a computer or an MCU) and a Host Controller (the actual Bluetoot chipset) follows the Host Controller Interface (HCI), see {@fig:HostChipsetConnection}. HCI defines how commands, events, asynchronous and synchronous data packets are exchanged, see [here]). Asynchronous packets (ACL) are used for data transfer, while synchronous packets (SCO) are used for Voice with the Headset and the Hands-free Profiles.
The communication between a Host (a computer or an MCU) and a Host Controller (the actual Bluetoot chipset) follows the Host Controller Interface (HCI), see {@fig:HostChipsetConnection}. HCI defines how commands, events, asynchronous and synchronous data packets are exchanged. Asynchronous packets (ACL) are used for data transfer, while synchronous packets (SCO) are used for Voice with the Headset and the Hands-Free Profiles.
![Host Controller to Host connection](picts/host_chipset_connection.png){#fig:HostChipsetConnection}
On desktop-class computers incl. laptops, USB is mainly used as HCI transport layer. On embedded systems, UART connections are used instead, although USB could be used as well.
On desktop-class computers incl. laptops, USB is mainly used as HCI transport layer. For USB Bluetooth chipsets, there is little variation: most USB dongles on the market currently contain a Broadcom BCM20702 or a CSR 851x chipset.
On embedded systems, UART connections are used instead, although USB could be used as well.
Most USB Bluetooth dongles on the market conatin either an Broadcom BCM20702
For UART connections, different transport layer variants exist. The most common one is the official "UART Transport", also called H4. It requires hardware flow control via the CTS/RTS lines and assumes no errors on the UART lines. The "Three-Wire UART Transport", also called H5, makes use of the SLIP protocol to transmit a packet and can deal with packet loss and bit-errors by retranssion. Finally, Texas Instruments created the "eHCILL transport" layer based on H4 that allows both sides to enter sleep mode without loosing synchronisation.
@ -15,14 +18,14 @@ Unfortunately, the HCI standard misses a few relevant details:
* Some Bluetooth chipsets don't have a unique MAC address. On start, the MAC address needs to be set, but there's no standard HCI command to set it.
* SCO data for Voice can either be transmitted via the HCI interface or via an explicit PCM/I2S interface on the chipset. Most chipsets default to the PCM/I2S interface. To use it via USB or for Wide-Band Speech in the Hands-Free Profile, the data needs to be delivered to the host MCU. Newer Bluetooth standards define a HCI command to configure the routing, but it is not implemented in the chipsets we've tested so far. Instead, this is configured in a vendor-specific way as well.
* SCO data for Voice can either be transmitted via the HCI interface or via an explicit PCM/I2S interface on the chipset. Most chipsets default to the PCM/I2S interface. To use it via USB or for Wide-Band Speech in the Hands-Free Profile, the data needs to be delivered to the host MCU. Newer Bluetooth standards define a HCI command to configure the SCO routing, but it is not implemented in the chipsets we've tested so far. Instead, this is configured in a vendor-specific way as well.
* In addition, most vendors allow to patch their chipsets at run time by sending patch comands to the chipset. Obviously, this is also vendor dependent.
* In addition, most vendors allow to patch or configure their chipsets at run time by sending custom comands to the chipset. Obviously, this is also vendor dependent.
The level of developer documentation and support varies widely between the various Bluetooth chipset providers.
From our experience, only Texas Instruments and EM Microelectronics provide all relevant information directly on their website. Nordic Semiconductor does not officially have Bluetooth chipsets with HCI interface, but their the documentation on their nRF5 series is complete and very informative. TI and Nordic also provide excellent support via their web forum.
From our experience, only Texas Instruments and EM Microelectronics provide all relevant information directly on their website. Nordic Semiconductor does not officially have Bluetooth chipsets with HCI interface, but their the documentation on their nRF5 series is complete and very informative. TI and Nordic also provide excellent support via their respective web forum.
Broadcom, whose Bluetooth + Wifi division has been acquired by the Cypress Semiconductor Corporation, provides developer documentation only to large customers as far as we know. It's possible to join their Community forum and download the WICED SDK. The WICED SDK is targeted at Wifi + Bluetooth Combo chipsets and contains the necessary chipset patch files.
@ -31,19 +34,42 @@ CSR, which has been acquired by Qualcomm, provides all relevant information on t
Chipset | HCI Transport | SCO over HCI | BTstack support | Comment
-------------------- | ---------------|------------------|-------------------|--------
Broadcom USB Dongles | USB | No (didn't work) | chipset/bcm |
Broadcom BCM43438 | H4, H5 | No (didn't work) | chipset/bcm | max UART baudrate 3 mbps
Broadcom UART | H4, H5 | No (didn't work) | chipset/bcm | Max UART baudrate 3 mbps
CSR 8x10, 8x11 | H4, H5 | No (didn't work) | chipset/csr |
CSR USB Dongles | USB | Yes | chipset/csr |
EM 9301 | SPI | n.a. | chipset/em9301 | LE only, custom HCI SPI implementation
Nordic nRF | H4 | n.a. | n.a. | LE only, requires HCI firmware
STM STLC2500D | H4 | No (didn't try) | chipset/stlc2500d | custom deep sleep management not supported
TC35661 | H4 | No (didn't try) | chipset/tc3566 | BLE patches missing
TI CC256x, WL183x | H4, H5, eHCILL | Yes | chipset/cc256x | also WL185x, WL187x, and WL189x
Nordic nRF | H4 | n.a. | n.a. | LE only, requires custom HCI firmware
STM STLC2500D | H4 | No (didn't try) | chipset/stlc2500d | Custom deep sleep management not supported
Toshiba TC35661 | H4 | No (didn't try) | chipset/tc3566 | HCI version not tested. Classic works.
TI CC256x, WL183x | H4, H5, eHCILL | Yes | chipset/cc256x | Also WL185x, WL187x, and WL189x
**Note** All Bluetooth Classic chipsets support SCO over HCI, for those that are marked with No, we either didn't try or didn't found enough information to configure it correctly.
## Broadcom
Before the Broadcom Wifi+Bluetooth division was taken over by Cypress Semiconductor, it was not possible to buy Broadcom chipset in low quantities. However, module manufacturers like Ampak created modules that contained Broadcom BCM chipsets (Bluetooth as well as Bluetooth+Wifi combos) that might already have been pre-tested for FCC and similar certifications.
A popular example is the Ampak AP6212A module that contains an BCM 43438A1 and is used on the Raspberry Pi 3, the RedBear Duo, and the RedBear IoT pHAT for older Rasperry Pi models.
The best source for documentation so far has been the source code for blueZ and the Bluedroid Bluetooth stack from Android.
Broadcom USB dongles do not require special configuration, however SCO data is not routed over USB by default.
**Init scripts**: For UART connected chipsets, an init script has to be uploaded after power on. For Bluetooth chipsets that are used in Broadcom Wifi+Bluetooth combos, this file often can be found as a binary file in Linux distributions with the ending *'.hcd'* or as part of the WICED SDK as C source file that contains the init script as a data array for use without a file system.
To find the correct file, Broadcom chipsets return their model number when asked for their local name.
BTstack supports uploading of the init script for both variants: file lookup by name in the posix-h4 port and linking against the init script in the WICED port.
**BD Addr** can be set with a custom command. A fixed addres is provided on some modules, e.g. the AP6212A, but not on others.
**SCO data** can be configured with a custom command found in the bluez sources. We haven't been able to route SCO data over HCI yet. Therefore, only HSP and HFP Narrow Band Speech is supported with BTstack via I2C/PCM pins currently.
**Baud rate** can be set with custom command. It is reset during the warm start after uploading the init script.
**BTstack integration**: The common code for all Broadcom chipsets is provided by *btstack_chipset_bcm.c*. During the setup, *btstack_chipset_bcm_instance* function is used to get a *btstack_chipset_t* instance and passed to *hci_init* function.
SCO Data can not be routed over HCI, so HFP Wide-Band Speech is not supported currently.
## CSR
## EM Microelectronic Marin
@ -64,7 +90,7 @@ The CC256x chipset is connected via an UART connection and supports the H4, H5 (
**BD Addr** can be set with [HCI_VS_Write_BD_Addr](2.2.1 HCI_VS_Write_BD_Addr (0xFC06)) although all chipsets have an official address stored.
**CC256x Init Scripts.** In order to use the CC256x chipset an initialization script must be obtained and converted into a C file for use with BTstack.
**Init Scripts.** In order to use the CC256x chipset an initialization script must be obtained and converted into a C file for use with BTstack.
The Makefile at *chipset/cc256x/Makefile* is able to automatically download and convert the requested file. It does this by:
@ -86,9 +112,9 @@ the naming scheme previously used on Linux systems. The conversion
script has been updated to also detect *initscripts_TIInit_6.7.16_bt_spec_4.1.bts*
and integrates *initscripts_TIInit_6.7.16_ble_add-on.bts* if present.
**BTstack integration**: The common code for all CC256x chipsets is provided by *btstack_chipset_cc256x.c*. During the setup, *btstack_chipset_cc256x_instance* function is used to get a *btstack_control_t* instance and passed to *hci_init* function.
**BTstack integration**: The common code for all CC256x chipsets is provided by *btstack_chipset_cc256x.c*. During the setup, *btstack_chipset_cc256x_instance* function is used to get a *btstack_chiopset_t* instance and passed to *hci_init* function.
SCO Data can be route over HCI, so HFP Wide-Band Speech is supported.
SCO Data can be routed over HCI, so HFP Wide-Band Speech is supported.
## Toshiba