modem

Modem support

Each particular class of modem has internal protocols needed for controlling it. So far, Synit is able to interact with generic Hayes-style (“AT-command”) modems, as seen in the PinePhone, as well as with the modem in the Samsung Galaxy S7.

Each modem’s internal protocol is spoken across the modem’s distinguished dataspace, a reference to which is held in the modem’s ModemPresent assertion.

Hayes-style (“AT-command”) Modems

As of October 2022, this protocol is implemented entirely in the SqueakPhone Smalltalk image, in class HayesModemActor and friends.

Presence

Hayes-style modems announce their presence with a subtype of the general ModemPresent assertion schema.

ModemPresent = <modem =hayes @devicePath string @dataspace #:InternalProtocol> .

(TODO: specify the InternalProtocol properly)

InternalProtocol = any .

Unsolicited Result Codes

An UnsolicitedResultCode message is sent when the modem sends us a “URC”, an Unsolicited Result Code.

UnsolicitedResultCode = <unsolicited @result Result> .

Executing AT commands

Assert a CommandRPC record to request execution of an AT command string. The completion, along with any responses, will be send to the replyTo entity reference. Alternatively, if no completion notification or response is desired, send a CommandEvent message.

CommandRPC = <execute-command @commandText string @replyTo #:CommandResult> .
CommandEvent = <execute-command @commandText string> .

The result of a command execution is asserted as a CommandResult record to the replyTo entity in the CommandRPC.

CommandResult = <command-result @commandText string @results [Result ...] @finalResult string> .

Responses and Unsolicited Results

The Result type appears in both UnsolicitedResultCode and CommandResult records.

Result = <result @text string @tag MaybeString @fields MaybeStrings> .
MaybeString = @present string / @absent #f .
MaybeStrings = @present [string ...] / @absent #f .

Examples. - <unsolicited <result "NO CARRIER" #f #f>> - <unsolicited <result "+CRING: VOICE" "CRING" ["VOICE"]>> - <unsolicited <result "+CLIP: \"+31655555555\",145,,,,0" "CLIP" ["+31655555555" "145" "" "" "" "0"]>> - <unsolicited <result "^DSCI: 2,1,4,0,+31655555555,145" "DSCI" ["2" "1" "4" "0" "+31655555555" "145"]>> - <unsolicited <result "+QIND: \"csq\",12,99" "QIND" ["csq" "12" "99"]>>

Samsung Galaxy S7

The Samsung Galaxy S7 was the first modem supported by Synit, but because of problems with the relevant PostmarketOS kernel, support for it has languished a bit while development has proceeded based around the PinePhone. As of October 2022, the Samsung modem support protocols are implemented entirely in the SqueakPhone Smalltalk image, in class SamsungGalaxyS7ModemActor and friends.

Presence

The modem announces its presence with a subtype of the general ModemPresent assertion schema.

ModemPresent = <modem =samsung-galaxy-s7 @devicePath string @dataspace #:InternalProtocol> .

(TODO: specify the InternalProtocol properly)

InternalProtocol = any .

Low-level packet I/O

ModemPacket = @in <from-modem @packet any> / @out <to-modem @packet any> .

# The bodies are instances of SamsungFmtMessage and SamsungRfsMessage, respectively.
FmtPacket = <fmt @body #:any> .
RfsPacket = <rfs @body #:any> .

Executing commands

Analogous to AT command execution for Hayes-style modems.

# Assertion. Asks the modem to execute the given command.
CommandRPC = <execute-command @command FmtPacket @replyTo #:FmtPacket> .
# Message. Asks the modem to execute the given command, but not to send back the reply.
CommandEvent = <execute-command @command FmtPacket> .

Copyright © 2021–2023 Tony Garnock-Jones, CC BY 4.0