Ticket #511 (Open)Fri May 14 13:40:53 UTC 2021
CM4 Lite RTC
| Reported by: | Chris Hall (132) | Severity: | Enhancement |
| Part: | RISC OS: General | Release: | |
| Milestone: | Status | Open |
Details by Chris Hall (132):
On CM4 lite the RTC is said to be connected to a different IIC bus and appears invisible to RISC OS.
Changelog:
Modified by Chris Hall (132) Wed, May 19 2021 - 17:33:59 GMT
The IIC bus for the RTC (PCF85063, not supported by RISC OS) on the I/O board is on GPIO 44/45 at address &A2. So this issue is really one that relates to the I/O board not the CM4 itself. The IIC pins on the GPIO header on the I/O board work OK.
Modified by Sprow (202) Fri, May 21 2021 - 21:10:05 GMT
For reference, the CMIO IIC bus comes out on GPIO44/45. It’s possible to mux IIC1 to those pins by editing IIC.s in the HAL sources
LDR a2, [a3, #GPFSel4] BICHS a2, a2, #8_00770000 ORRHS a2, a2, #8_00660000 ; Set FSEL to ALT2 on GPIO44/45 for Compute Module 4 STR a2, [a3, #GPFSel4]however this then means the IIC bus that appears on the GPIO header disappears (IIC1 when it’s muxed to GPIO2/3).
Some options:
- Use IIC0 for GPIO44/45
- Bitbash IIC on GPIO44/45
But then: - RISC OS only looks on logical bus 0 for some things
- A driver is needed for the PCF85063 RTC chip (there’s also a fan controller on the CMIO board)
Modified by Sprow (202) Fri, May 21 2021 - 21:10:46 GMT
- Part changed from Unspecified to RISC OS: General
Modified by Sprow (202) Sat, May 22 2021 - 10:31:04 GMT
- Severity changed from Normal to Enhancement
