Decoding errors

[ryaneastland-zz]

Probably just my not knowing how to set everything up right but I keep ever getting NUL at the end on messages received or Ä instead of [ and Ü instead of ] any ideas.

I'm running on a raspberry pi with rtl_fm input

command
rtl_fm -f 148.9125M -s 22050 | multimon-ng -t raw -a POCSAG512 -f alpha /dev/stdin

[marshyonline]

Not just you, I am also getting this.

[ryaneastland-zz]

I've worked out it's something to do with the charset that multimon is using so just do a find/replace for the incorrect letters

[EliasOenal]

I'm still waiting for someone to implement this, without completely breaking support for the German charset. Please see #65 and #21

[pyrog]

Hi,
Same issue with "french" charset.
Swissphone pagers use the following charset:

• FTZ Germany
• US ASCII
• Norway / Danmark
• Switzerland
• Sweden / Finland
• Spain
• France
• Britain
• International
• Italy
• Slovenia

Tested with a Swissphone DE700 pager set with French charset:

• Input of rpitx/pocsag

 !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7F

• Output of multimode-ng

!#$%&'()*+,-./0123456789:; = ?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[Ö]^_`abcdefghijklmnopqrstuvwxyzäöüß

• Message displayed on the DE700

 !"#$%&'()*+,-./0123456789:;<=>?àABCDEFGHIJKLMNOPQRSTUVWXYZâç§^_`abcdefghijklmnopqrstuvwxyzéùèê¡

(DEL character is displayed as an inverted exclamation mark)

Hex	US	FR	DE
40	@	à	@

Hex	US	FR	DE
5b	[	â	Ä
5c	\	ç	Ö
5d	]	§	Ü

Hex	US	FR	DE
7b	{	é	ä
7c	⎜	ù	ö
7d	}	è	ü
7e	~	ê	ß
7F	␡	¡	␡

DEL is displayed as <DEL> by multimode-ng

[pyrog]

According to NZ Telepermit for pagers, the POCSAG charset is ISO 646 with US / IRV (1991) variant (ISO-IR-006).

All other variant are described in the ISO/IEC_646 Variant comparison chart.

According to DecentralizedAmateurPagingNetwork/Core issue #143, AlphaPoc pager used by hams use the DE variant (ISO-IR-021).

[pyrog]

Variant	Code Chart	24	40	5B	5C	5D	5E	5F	60	7B	7C	7D	7E
US / IRV (1991)	ISO-IR-006	#	@	[	\	]	^	_	`	{	|	}	~
DE	ISO-IR-021	#	§	Ä	Ö	Ü	^	_	`	ä	ö	ü	ß
swi (NRCS)	CP01021	ù	à	é	ç	ê	î	è	ô	ä	ö	ü	û
FR (1983)	ISO-IR-069	£	à	°	ç	§	^	_	µ	é	ù	è	¨
CA	ISO-IR-121	#	à	â	ç	ê	î	_	ô	é	ù	è	û
DE700		$	à	â	ç	§	^	_	`	é	ù	è	ê
TPL		$	à	°	ç	§	^	_	`	é	ù	è	‾

DE700 and TPL pagers with french charset seem to use a mix of FR and CA ISO 646 charset.

[EliasOenal]

Thanks for posting that table. Would you be willing to change the default to US and implement a command line flag allowing the selection of the other charsets?

[pyrog]

In pocsag.c#L129 we could use a simple global trtab[128] and remove the binary search.
So the --charset option "just" set the appropriate tab once…

[EliasOenal]

Fine with me.

[eopo]

Same error here but inverted.
German messages with Umlauts. Pager displays Ü, multimon_ng outputs ']' (closing square bracket)

[pyrog]

@shutterfire Do you have a technical manual for this pager with the charset(s) used?

Or could you send this test message with rpitx ?

printf "1234567A:Test charset \x24\x40\x5B\x5c\x5d\x5e\x5f\x60\x7b\x7c\x7d\x7e" | sudo ~/src/rpitx/pocsag -f BOS_FREQUENCY -r BOS_BAUD_RATE

[pyrog]

I don't add yet charsets for EuroBos, Swissphone and TPL pagers.

Should we add ?

• a charset option tpl-DE, tpl-FR, eurobos-DE, eurobos-FR…
• a config file to specify the "user" charset
• …

TPL seem to use the FR (1973) also called ISO-IR-025 (except £).

[pyrog]

Several characters could be used as combining characters, when preceded or followed with a backspace C0 control. This is attested in the code charts for IRV, GB, FR1, CA and CA2, which note that "',^ would behave as the diaeresis, acute accent, cedilla and circumflex (rather than quotation marks, a comma and an upward arrowhead) when preceded or followed by a backspace. The tilde character (~) was similarly introduced as a diacritic (˜).

Source : https://en.wikipedia.org/wiki/ISO/IEC_646#Variant_comparison_chart

Tested with TPL and Swissphone pager with french charset:

printf "1234567A:Test E\x08^ ^\x08E \x08^E E^\x08" | sudo rpitx/pocsag…

That don't work: 😁

• TPL display Test Eî^ ^îE î^E E^î
• Swissphone display Test E ^ ^ E ^E E^

[pyrog]

Send characters from 0x00 to 0x1f with the following script:

printf "1234567A:Test 0x1f (\x1f)" | sudo rpitx/pocsag …

(Note: both pagers use the french charset).

• Swissphone pager display a Whitespace character except for 0x00 and 0x0A as it end the message.
• TPL pager display the following characters:

Code	Char	Comment
0x00		end of message
0x01		Whitespace character
0x02		new line
0x03	£	Pound sign
0x04	¯	Macron
0x05	ë	Latin Small Letter E with diaeresis
0x06	Ü	Latin Capital Letter U with diaeresis
0x07	ê	Latin Small Letter E with circumflex
0x08	î	Latin Small Letter I with circumflex
0x09	â	Latin Small Letter A with circumflex
0x0a		end of message
0x0b	ô	Latin Small Letter O with circumflex
0x0c	ï	Latin Small Letter I with diaeresis
0x0d		new line
0x0e	°	Degree symbol
0x0f	ç	Latin Small Letter C with cedilla
0x10	§	Section sign
0x11	é	Latin Small Letter E with acute
0x12	ù	Latin Small Letter U with grave
0x13	è	Latin Small Letter E with grave
0x14	¡	Inverted Exclamation Mark
0x15	Ç	Latin Capital letter C with cedilla
0x16	Ñ	Latin Capital letter N with tilde
0x17	¿	Inverted Question Mark
0x18	ñ	Latin Small Letter N with tilde
0x19	Ä	Latin Capital letter A with diaeresis
0x1a	Ö	Latin Capital letter O with diaeresis
0x1b		Whitespace character
0x1c	ä	Latin Small Letter A with diaeresis
0x1d	ö	Latin Small Letter O with diaeresis
0x1e	ü	Latin Capital Letter U with diaeresis
0x1f	ß	Latin Small Letter sharp S