Jwy-jump / pyGRMON

Usage of the UART master of the GR718B

pyGRMON

Usage of the UART master of the GR718B

UART Interface

The protocol allows a read or write transfer to be generated to any address on the AMBA AHB bus

Transmission protocol

The interface supports a simple protocol where commands consist of a control byte, followed by a 32-bit address, followed by optional write data.

READ command

We have to transmit a read command, the header is:

Byte	Value	Description
0	b'01' & Length	10 -> Denotes Command Read; L[5..0] Is the number of words to read: Length-1
1	Addr 31..24	Addr 31..24
2	Addr 23..16	Addr 23..16
3	Addr 15..08	Addr 15..8
4	Addr 07..00	Addr 7..0

Read Example: Read Version / instance ID regiser (RTR.VER) AMBA Addr: 0xFFF20A08 RMAP Addr: 0x00000A08

Byte	Value	Description
0	80	Read Command. Read Lenth = 1 Word.
1	FF	AMBA ADDR = 0xFFF20A08
2	F2
3	0A
4	08

Command : 0x80 0xFF 0xF2 0x0A 0x08 Expected Result: 0x01 0x03 0x00 0x00

31 24	23 16	15 8	7 4	3 0
MA	MI	PA	ID
0x01	0x03	0x00	0x0	*

31: 24 Major version (MA) - Holds the major version number of the router. Constant value 0x01. 23: 16 Minor version (MI) - Holds the minor version number of the router. Constant value 0x03. 15: 8 Patch (PA) - Holds the patch number of the router. Constant value 0x00. 7: 0 Instance ID (ID) - Holds the instance ID number of the router. Reset value for bits 3:0 is set through GPIO[23:0] pins, as specified in section 5.

Write command

Write the register Addr with value.

Write Exmaple: Write Spw2 ctrl (RTR.PCTRL) AMBA Addr: 0xFFF20808 RMAP Addr: 0x00000A08 Value: 0x081404F0

Byte	Value	Description
0	C0	Write Command. Write Lenth = 1 Word.
1	FF	AMBA ADDR = 0xFFF20A08
2	F2
3	0A
4	08
5	08
6	14
7	04
8	F0
Command: 0xC0 0xFF 0xF2 0x0A 0x08 0x08 0x14 0x04 0xF0

Install

Requires Python3, pySerial.

$]# sudo python3 -m pip install pyserial